JUDGMENT NO. 145

YEAR 2026

ITALIAN REPUBLIC

IN THE NAME OF THE ITALIAN PEOPLE

THE CONSTITUTIONAL COURT

composed of:

President: Giovanni AMOROSO;

Judges: Francesco VIGANÒ, Luca ANTONINI, Stefano PETITTI, Angelo BUSCEMA, Emanuela NAVARRETTA, Maria Rosaria SAN GIORGIO, Filippo PATRONI GRIFFI, Marco D’ALBERTI, Giovanni PITRUZZELLA, Massimo LUCIANI, Roberto Nicola CASSINELLI, Francesco Saverio MARINI,
has pronounced the following

JUDGMENT

in proceedings concerning the constitutional legitimacy of Article 12 of Law No. 91 of June 13, 2025 (Delegation to the Government for the transposition of European directives and the implementation of other European Union acts - European Delegation Law 2024), brought by the Region of Lombardy with an appeal notified on August 22, 2025 and filed in the registry on the same date; by the Region of Piedmont with an appeal notified on August 25, 2025 and filed in the registry on the same date; by the Region of Veneto, with an appeal notified on August 25, 2025 and filed in the registry on the same date, respectively registered under numbers 34, 35, and 36 of the 2025 appeal registry and published in the Official Journal of the Republic No. 40, first special series, for the year 2025.

Having regard to the appearance entries of the President of the Council of Ministers;

having heard in the public hearing of May 6, 2026, the Judge Rapporteur Massimo Luciani;

having heard counsel Piera Pujatti for the Region of Lombardy, Giacomo Quarneti for the Region of Veneto, and Marcello Cecchetti for the Regions of Piedmont and Veneto, as well as State attorneys Giovanni Palatiello and Giuseppe Lillo for the President of the Council of Ministers;

deliberated in the chambers on May 6, 2026.

Ritenuto in fatto

1.– By an initial appeal registered under No. 34 of the 2025 appeal registry, notified and filed on August 22, 2025, and by two other appeals, substantially overlapping in content, registered under numbers 35 and 36 of the 2025 appeal registry, notified and filed on August 25, 2025, the Regions of Lombardy, Piedmont, and Veneto brought multiple questions of constitutional legitimacy regarding Article 12 of Law No. 91 of June 13, 2025 (Delegation to the Government for the transposition of European directives and the implementation of other European Union acts - European Delegation Law 2024), which sets forth principles and guiding criteria for the exercise of the legislative delegation conferred upon the Government for the transposition of Directive (EU) 2024/2881 of the European Parliament and of the Council of October 23, 2024, on ambient air quality and cleaner air for Europe.

1.1.− By the first ground of its appeal, the Region of Lombardy alleges the constitutional illegitimacy of Article 12 of Law No. 91 of 2025 for violation of Articles 5 and 120, second paragraph, of the Constitution, arguing that, owing to the omission of obtaining the opinion of the Permanent Conference for the Relations between the State, the Regions, and the Autonomous Provinces of Trento and Bolzano, the principle of loyal cooperation was violated.

The appellant premises that, according to this Court, the delegation law is not exempt from the principal review of constitutional legitimacy (in this regard, reference is made to judgments No. 261 of 2017, No. 251 of 2016, and No. 205 of 2005) and that the application of the principle of loyal cooperation is inescapable, in forms allowing adequate involvement of the regions, where the regulated subject matter is characterized by an intertwining of exclusive state, concurrent, and residual legislative competences (reference is made to judgment No. 72 of 2019).

According to the appellant, the intertwining of different material areas cannot be resolved by reference to the concept of prevalence – reference is made again to judgment No. 172 (recte: No. 72) of 2019 – such that the circumstance that the matter regulated by Article 12 of Law No. 91 of 2025 falls within the domain of environmental protection cannot cause the coexistence of other matters falling within regional competences to be overlooked.

In particular, «the provision not to implement» regional cooperation during the delegation phase would conflict with Article 5 of the Constitution, which requires the State, inter alia, to adapt «the principles and methods of its legislation to the requirements of autonomy and decentralization».

1.2.− By the second ground of its appeal, the Region of Lombardy alleges the constitutional illegitimacy of Article 12, paragraph 2, of Law No. 91 of 2025, for violation of the principle of loyal cooperation under Articles 5 and 120, second paragraph, of the Constitution, insofar as it provides that the legislative decrees referred to in paragraph 1 of the same provision shall be adopted upon receiving the opinion of the Unified Conference referred to in Article 8 of Legislative Decree No. 281 of August 28, 1997 (Definition and expansion of the attributions of the Permanent Conference for the Relations between the State, the Regions and the Autonomous Provinces of Trento and Bolzano and unification, for matters and tasks of common interest to regions, provinces, and municipalities, with the State-City and Local Autonomies Conference), rather than upon prior agreement (intesa).

The curtailment of regional consultation «during the enactment phase of the legislative decree» would have «no counterbalance in the procedure for the enactment of the legislative decree». This ground of appeal is presented in continuity with the first, as it highlights that the overall delegation law–legislative decree system regulates domains characterized by the intertwining of state and regional competences without ensuring effective forms of coordination with the regions.

According to the appellant, regional involvement would prove insufficient, since the intertwining of the competences affected by the regulation would have required, instead of a merely consultative contribution, recourse to an agreement (intesa) as the sole instrument capable of ensuring effective participation of regional autonomies in the determination of the relevant contents (reference is made to the judgments of this Court No. 130 of 2024, No. 72 and No. 56 of 2019, and No. 251 of 2016). This is all the more true considering that the State would shift full responsibility (on an ordinary basis) for air quality planning onto the regions.

1.2.1.− Furthermore, the Region of Piedmont and the Region of Veneto, by the third ground set forth in the appeals registered under numbers 35 and 36 of the 2025 appeal registry, challenge the constitutional legitimacy of Article 12, paragraph 2, of Law No. 91 of 2025 for violation of Articles 5 and 120, second paragraph, of the Constitution.

The appellants argue that the challenged provision is constitutionally illegitimate because, notwithstanding multiple interferences with regional competences that cannot be resolved through the criterion of the prevalence of state law, it provides for the mere opinion of the Unified Conference for the adoption of delegated legislative decrees, rather than an agreement (intesa) within the State-Regions Conference, which is the only form of coordination capable of guaranteeing effective involvement of regional autonomies.

The state legislature omitted to consider the peculiar position of regional entities and their respective constitutional competences, which are inevitably involved in the adoption of policies and measures necessary to guarantee air quality standards established at the European level, both regarding the collaborative venue designated (the Unified Conference instead of the State-Regions Conference) and – even more so – regarding the intensity of the chosen form of collaboration (a mere opinion instead of an agreement).

The Regions of Piedmont and Veneto premise awareness of this Court's orientation according to which, in principle, the necessity of loyal cooperation in the adoption of state legislative acts is to be excluded, but they add that, nonetheless, precisely with reference to the adoption of legislative decrees, this Court, starting from judgment No. 251 of 2016, affirmed that «[w]hereas, however, the delegated legislator sets out to reform institutions affecting inextricably connected state and regional competences, the need arises to resort to an agreement (intesa)».

The appeals of the Regions of Piedmont and Veneto argue that, although Directive 2024/2881/EU on air quality falls within the European Union's competence in environmental matters, also pursuant to Article 192, paragraph 1, of the Treaty on the Functioning of the European Union, cited as the legal basis by the directive itself, it would be reductive to consider that its implementation in national legal orders – and thus the definition of strategies, instruments, and measures – can be automatically traced back to the exclusive legislative competence of the State in matters of environmental and ecosystem protection, pursuant to Article 117, second paragraph, letter s), of the Constitution, based on a presumed criterion of prevalence.

In the field of air quality, an essential distinction exists: «on the one hand, regulations establishing standards to be respected and results to be achieved, control and measurement parameters for necessary compliance verifications, as well as timelines and updates to technical-scientific progress [...]; on the other hand, however, those very regulations – which in themselves are certainly attributable to "environmental protection" – necessarily require, under penalty of their definite inefficacy and ineffectiveness, the activation of strategic policies of extraordinary variety and complexity that affect, through appropriate instruments and measures specifically addressed to the undeniable multiplicity of factors impacting air quality, the broadest fields of anthropogenic activities producing emissions into the atmosphere, extending from industrial and commercial activities, to energy production and consumption, agricultural activities, mobility and transport intermodality, heating/cooling of civil buildings, urban planning of the territory, as well as obviously public health, tourism, scientific research, and technological innovation». This approach is also confirmed by the state legislature itself (reference is made to Article 12, paragraph 1, letter a, of Law No. 91 of 2025), which mandates coordination between air quality policies and those relating to major emission sources.

According to the appellants, the constraint to provide ordinarily for regional and local legislative competence for air remediation measures, reserving to the State a merely complementary role in limited cases, highlights the inadequacy of a simple opinion within the Unified Conference to guarantee the proper design of the distribution of competences, thereby rendering an agreement (intesa) within the State-Regions Conference necessary.

1.3.− By the third ground of its appeal, the Region of Lombardy contends that Article 12 of Law No. 91 of 2025 is constitutionally illegitimate for violation of Article 117, third and fourth paragraphs, of the Constitution (referred to on one occasion in the appeal as the second and third paragraphs), and of the principle of loyal cooperation, also as a «consequence of what has been set forth in the preceding grounds, with reference to the violation of the principle of loyal cooperation».

More specifically, the appeal states: «the concept of synergy, referred to in the challenged Article 12, is strictly connected to forms of cooperation; which implies the integration of competences. But the one-way synergy conceived by Article 12 of Law No. 91/2025 will have a direct impact on the planning of other regional domains (health protection, transport, energy). In this sense, the constitutional illegitimacy of Article 12 is emphasized from this perspective as well».

1.4.− By the fourth ground of its appeal, the Region of Lombardy alleges the constitutional illegitimacy of Article 12 of Law No. 91 of 2025 also for violation of Article 3 of the Constitution, as regards reasonableness, Article 97 of the Constitution, as regards sound administration, and Article 118 of the Constitution, as regards adequacy.

The provision would establish synergies between «regional measures for the remediation of air quality undertaken "ordinarily" by the Regions» and a subsidiary state intervention, activable only in the event of insufficiency of regional measures, without indicating timelines, participatory procedures, and adequate coordination mechanisms, thereby failing to guarantee sufficient protection of regional interests. This conflicts with Article 97 of the Constitution, which must be construed as imposing the «establishment of organizational structures and modules aimed at ensuring optimal functionality».

State and regional action would thus proceed on parallel planes, without spaces for co-decision or even coordination. The sole exception to this scheme would be the conclusion of an agreement signed by the interested regional authorities and all state authorities competent over the relevant emission sectors; however, regarding this aspect, the implementation of the delegation would be left to the initiative of individual authorities, compelling the delegated legislature to de facto shift the exercise of the regulatory function from the Government in its collegial capacity to individual ministers or individual competent state authorities (reference is made to judgment of this Court No. 104 of 2017).

The appellant argues that Article 12 of Law No. 91 of 2025 appears to reiterate the model introduced by Legislative Decree No. 155 of August 13, 2010 (Implementation of Directive 2008/50/EC on ambient air quality and cleaner air for Europe), although the latter has already been deemed insufficient by the European Union (reference is made to «infringement procedures No. 2014/2147, No. 2015/2043, and No. 2020/2299 against Italy for the incorrect application of Directive 2008/50/EC with reference to continuous and long-term exceedances of limit values for particulate matter PM10, nitrogen dioxide, and particulate matter PM2.5», as well as Court of Justice of the European Union, Grand Chamber, judgment of November 10, 2020, Case C-644/18, European Commission, and Seventh Chamber, judgment of May 12, 2022, Case C-573/19, European Commission).

According to the Region of Lombardy, «the mere reproduction of the prior model, with the addition of "synergy"», devoid of regional consultation, proves irrational and unsuitable to guarantee the attainment of European standards, in the absence of an effective system of institutional collaboration.

Furthermore, in the appellant's view, the challenged provision appears to move in the opposite direction to the resolution of the Council of Ministers of June 20, 2025 (National Action Plan for the Improvement of Air Quality), which establishes the commitment of all administrations identified by Article 14, paragraph 5, of Decree-Law No. 131 of September 16, 2024 (Urgent provisions for the implementation of obligations deriving from European Union acts and pending infringement and pre-infringement procedures against the Italian State), converted, with amendments, into Law No. 166 of November 14, 2024, «to cooperate in identifying future national strategies in order to guarantee greater protection of ambient air quality», leaving to the regions the drafting of plans not preceded by coordinated examinations among different institutional levels, in the presence of an ormai acclarata (already acknowledged) particularity of the so-called "Po Valley" due to its orographical and climatic situation (reference is made to the principle and guiding criterion set forth in letter d of Article 10 of Law No. 7 of July 7, 2009, No. 88, bearing «Provisions for the fulfillment of obligations deriving from Italy's membership of the European Communities - Community Law 2008»).

The Region of Lombardy further states that: «[s]ound administration presents areas of overlap and competition with different constitutional values, but, in a matter exhibiting such a marked intertwining of competences, the claim to establish "synergies" without any regional involvement in determining the delegated provision conflicts with Article 118 of the Constitution, for failure of the state regulation to implement any consultation concerning the adequacy of the provision» and that «[t]here is a well-founded doubt in this regard concerning the reasonableness of such a choice, with consequent violation of Article 3 of the Constitution and, once again, violation of the principle of loyal cooperation between the State and the Regions, due to lack of proportionality and logical correspondence with the declared purposes, and due to irrationality to the extent that ex ante collaboration between the State and the Regions is not provided for».

1.5.− By the fifth and final ground of its appeal, the Region of Lombardy alleges the constitutional illegitimacy of Article 12, paragraph 3, of Law No. 91 of 2025, insofar as it provides that «[n]o new or greater burdens on public finance shall derive from the implementation of this article. Competent administrations shall meet the related obligations using human, instrumental, and financial resources available under current legislation». This provision follows the establishment that regions are ordinarily responsible for adopting air quality remediation measures in the environment. The provision would violate Articles 81, 97, and 119 of the Constitution (with a passing reference also to Article 119, fifth paragraph) as it lacks adequate financial coverage and would infringe upon the principles of coordination of public finance, sound administration, balanced budget, and regional prerogatives, rendering the contemplated intervention unfeasible in practice, also in light of the coverage obligations provided for by Article 17, paragraph 2, of Law No. 196 of December 31, 2009 (Law on Accounting and Public Finance).

The appeal also reads: «[t]he provision is moreover gravely detrimental to the balanced budget principle referred to in Article 81 of the Constitution, as well as to the aforementioned principles of reasonableness, sound administration, and adequacy referred to in Articles 3, 97, and 118 of the Constitution» and «[n]on-existent financial endowment cannot accompany reorganization proposals like those indicated in the delegation law and interrupts the necessary correspondence between allocated resources and exercised functions. Once again, in conflict with the principle of reasonableness referred to in Article 3 of the Constitution due to the absence of reorganizational or reallocative measures of resources» (reference is made to the judgments of this Court No. 272, No. 188 of 2015, and No. 1 of 2014).

For completeness, and as further demonstration of the constitutional illegitimacy of the challenged provision, the Region of Lombardy emphasizes that the regions had already pointed out, during the State-Regions Conference on the text that would result in the aforementioned resolution of the Council of Ministers of June 20, 2025, the inadequacy of state resources and that the achievement of European Union targets for 2030 «postulates going beyond actions on best available technologies and directly influencing behaviors», entailing massive investments to be borne by the regions.

1.5.1.− Furthermore, the Regions of Piedmont and Veneto, by the fourth ground of their appeals, allege the constitutional illegitimacy of Article 12, paragraph 3, of Law No. 91 of 2025, for violation of Articles 81, third paragraph, and 119, fourth paragraph, of the Constitution (or, as the appellants specify, Articles 3, 97, and 117, first paragraph, of the Constitution).

According to the appellant Regions, the provision, by imposing a financial invariance clause upon the Government for the implementation of legislative decrees, evades the obligation to cover the costs of new functions necessary to properly implement Directive 2024/2881/EU, in violation of the principle of correspondence between resources and functions, which requires the State to guarantee territorial entities full financing of the competences conferred upon them (Articles 81, third paragraph, and 119, fourth paragraph, of the Constitution), «or, alternatively, claims "effectively" and "seriously" to bind the delegated legislature to implement the obligations deriving from the directive in question without new or greater burdens on public finance», contradicting the purposes of the delegation and hindering the proper fulfillment of European obligations (reference is made to Articles 3, 97, and 117, first paragraph, of the Constitution).

The appeals highlight that the challenged provision has a special nature regarding the transposition and implementation of the aforementioned Directive 2024/2881/EU and has the effect of derogating from the general regulation of financial burdens provided for by Article 1, paragraph 3, of Law No. 91 of 2025. It would allow legislative decrees to provide for «any expenses not contemplated by current laws and which do not concern the ordinary activity of state or regional administrations», within the limits necessary for the fulfillment of European obligations, providing coverage through funds already allocated or, failing that, through the fund for the transposition of European legislation. Should the resources of such fund prove insufficient, decrees entailing new or greater burdens may be enacted only after the entry into force of «[l]egislative provisions allocating the necessary financial resources, in compliance with Article 17, paragraph 2, of Law No. 196 of December 31, 2009» (reference is made to the content of Article 17, paragraph 2, of Law No. 196 of 2009).

The appellants observe that, considering the «epochal» and unprecedented objectives of Directive 2024/2881/EU on air quality, it is evident that the adaptation of the Italian legal order – which is already non-compliant with less stringent standards today – would not be realistically possible without new resources. Consequently, the financial invariance clause is constitutionally illegitimate.

More specifically, according to the appellants, either "zero-cost" implementation is demanded, thus fundamentally compromising – however – the purpose of the delegation and the fulfillment of European obligations (in violation of Articles 3, 97, and 117, first paragraph, of the Constitution), or the necessity of new burdens is admitted, without however being able to quantify and cover them due to the imposed constraint, thereby evading Articles 81, third paragraph, and 119, fourth paragraph, of the Constitution.

1.6.− The Regions of Piedmont and Veneto, by the first ground of their appeals, also allege the constitutional illegitimacy of Article 12, paragraph 1, letter b), of Law No. 91 of 2025, for violation of Article 117, second paragraph, letter s), of the Constitution, with reference to the matter of «environmental and ecosystem protection», as well as Article 118, first paragraph, of the Constitution and the principles of subsidiarity, differentiation, and adequacy contemplated therein, concerning the correct allocation of administrative functions among the territorial entities of the Republic.

More specifically, according to the appellants, Article 12, paragraph 1, letter b), of Law No. 91 of 2025 is constitutionally illegitimate because, by mandating the ordinary attribution of air remediation measures to regional and local authorities and limiting state intervention solely to cases where «regional plans cannot allow the achievement of air quality values in areas influenced, in a determining manner, by emission sources over which the regions have no administrative and legislative competence» and «the contents of the measures are defined in agreements signed by the interested regional authorities and all state authorities competent over the relevant emission sectors», it ignores the proven inadequacy of such levels to guarantee European standards – especially in the Po Valley. This would conflict with the exclusive legislative competence of the State in environmental protection (Article 117, second paragraph, letter s, of the Constitution) and with the principles of subsidiarity, differentiation, and adequacy (Article 118, first paragraph, of the Constitution), which require such functions to be attributed to the State when regional levels prove structurally unsuitable, especially when, due to «natural causes» linked to the peculiar orographical conformation and meteoclimatic situation of the territories, regional levels are "physiologically” unsuited to independently face and manage phenomena that by origin, scope, or effects transcend the territorial spheres proper to the regions.

According to the appellants, Article 12 of Law No. 91 of 2025 purports to bind the delegated legislature to reproduce the model for the distribution of competences in air quality matters previously introduced by Legislative Decree No. 155 of 2010 during the implementation of the previous Directive 2008/50/EC of the European Parliament and of the Council of May 21, 2008, on ambient air quality and cleaner air for Europe.

The appeals emphasize that Legislative Decree No. 155 of 2010, implementing Law No. 88 of 2009, should have considered the specific criticality of pollution in the Po Valley, since Article 10 of Law No. 88 of 2009, in paragraph 1, letter d), contemplated a specific principle and guiding criterion expressly addressing the peculiarities of atmospheric pollution phenomena within such territories.

However, this criterion remained unimplemented: the legislative decree left management to the ordinary model, based on interregional coordination and state interventions only on an eventual basis and upon request by the regions. In the appellants' view, the fifteen-year experience of the competence-distribution model provided for by Legislative Decree No. 155 of 2010 – which the new delegation mandates to replicate – has now incontrovertibly demonstrated its inadequacy, especially regarding pollution in the Po Valley. Such inefficacy has been ascertained both at the European level (reference is made to the infringement procedures initiated by the European Commission No. 2014/2147, No. 2015/2043, and No. 2020/2299 for the incorrect application of Directive 2008/50/EC) and through judgments condemning the State for failure to fulfill obligations by the Court of Justice (reference is made to Seventh Chamber, judgment of May 12, 2022, C-573/19, European Commission, with reference to infringement procedure No. 2015/2043; Grand Chamber, judgment of November 10, 2020, C-644/18, European Commission, with reference to infringement procedure No. 2014/2147; First Chamber, judgment of December 19, 2012, Case C-68/11, European Commission), and at the national level, through regulatory interventions and institutional agreements culminating in the adoption, in 2025, of the aforementioned «National Action Plan for the Improvement of Air Quality 2025-2027».

The appellants highlight that, most recently, on March 13, 2024, in relation to the execution of CJEU judgment of November 10, 2020, C-644/18, and thus within the framework of infringement procedure No. 2014/2147 concerning exceedances of the daily and annual limit values established for PM10 particulate concentrations, the European Commission sent a letter of formal notice to the Italian authorities pursuant to Article 260, paragraph 2, TFEU, foreshadowing a new appeal to the EU Court of Justice for a declaration of failure to properly execute the judgment and consequent order to pay the resulting sanctions.

Furthermore, the appellants recall the program agreements and memoranda of understanding concluded between state administrations and the regions and the Autonomous Provinces of Trento and Bolzano starting from 2013, precisely following the EU Court of Justice judgment of December 19, 2012.

Reference is also made to Decree-Law No. 121 of September 12, 2023 (Urgent measures regarding air quality planning and road traffic limitations), converted, with amendments, into Law No. 155 of November 6, 2023, which, in Article 1, in order to execute the aforementioned Court of Justice judgments of November 10, 2020, and May 12, 2022 (paragraph 1), authorized the regions of the Po Valley to introduce extraordinary road traffic limitation measures, and thus in areas otherwise outside their competence, as well as further measures aimed at reducing harmful emissions (paragraphs 2 and 2-bis). Subsequently, Article 14 of Decree-Law No. 131 of 2024 (cited hereafter in the text resulting from the conversion law), last amended by Article 15-bis of Decree-Law No. 25 of March 14, 2025 (Urgent provisions regarding recruitment and functionality of public administrations), converted, with amendments, into Law No. 69 of May 9, 2025, provided for a funded program for sustainable mobility in areas where exceedances of air quality limit values relating to PM10 particulate matter and nitrogen dioxide NO2 had been ascertained (paragraphs 1 to 3) and established a control room (cabina di regia) at the Presidency of the Council of Ministers, tasked with drafting a «National Action Plan for the Improvement of Air Quality, including a timeline», indicating the administrations competent for its implementation (paragraphs 4 to 10).

In implementation precisely of this legislation, the aforementioned National Action Plan for the Improvement of Air Quality 2025-2027 was adopted (the appellants quote certain contents of the Plan).

The appellants point out that the Plan, as required by Article 14, paragraph 6, of Decree-Law No. 131 of 2024, and as reiterated by Article 1, paragraph 2, of the resolution of the Council of Ministers that adopted it, identifies for each measure the administrations entrusted with its implementation. This reveals a design contrary to the model outlined by Article 12, paragraph 1, letter b), of Law No. 91 of 2025: out of 29 actions, only one is entrusted exclusively to the regions, while all others involve at least one state administration. This would confirm the need for a direct and primary role of the State – not merely complementary – in managing atmospheric pollution and in air quality policies.

In the appellants' opinion, it is therefore evident that the delegation criterion providing for the ordinary attribution of air quality measures to regional and local authorities, relegating the State to a merely complementary role, is constitutionally illegitimate, especially concerning measures regarding the Po Valley. It would violate Articles 117, second paragraph, letter s), and 118, first paragraph, of the Constitution, which require the State to exercise its competences ordinarily and to allocate functions that regions are unable to perform adequately to the supra-regional level. In particular, the provision would be constitutionally illegitimate because it fails to provide for the direct competence of the State in cases where, due to the nature of the phenomena, interventions of an ultra-regional dimension are necessary.

1.7.− By the second ground of their appeals, the Regions of Piedmont and Veneto allege the constitutional illegitimacy of Article 12, paragraph 1, letter b), of Law No. 91 of 2025 also «for the same reasons and on the same terms indicated in the preceding censure [first ground of appeal]», as well as for violation of Articles 3, 97, and 117, first paragraph, of the Constitution, in relation to Directive 2024/2881/EU, with the concomitant indirect infringement of regional legislative and administrative competences under Articles 117, third and fourth paragraphs, and 118 of the Constitution.

In particular, the appellants argue that this provision prevents, in an irrational manner contrary to the principle of sound administration, both the regions of the Po Valley and the State from achieving the objectives of Directive 2024/2881/EU. The regions would thus be compelled to exercise their attributions (in matters of concurrent competence «health protection», «national production, transport, and distribution of energy», «territorial governance», as well as in the residual matters «agriculture» and «local public transport») in a constitutionally illegitimate manner, assuming the relative responsibilities. The distribution criterion provided for would therefore be structurally inadequate to guarantee compliance with European obligations and would consequently violate Articles 3, 97, and 117, first paragraph, of the Constitution, indirectly infringing regional legislative competences.

In summary, the constitutional illegitimacy of the delegation provision, conflicting with Articles 3, 97, and 117, first paragraph, of the Constitution, would inevitably entail an indirect infringement of the legislative competences of the appellants, who would be forced to exercise them through acts vitiated by derived illegitimacy for violation of the same constitutional parameters.

The appellants specify that the second ground of appeal is based on the same premises as the first, while placing before this Court the direct violation of substantive constitutional parameters rather than competence-related ones.

In conclusion, it is observed that, in such a context, it is evident that the challenged delegation provision, in seeking to replicate the competence-distribution system of Legislative Decree No. 155 of 2010 – which had already proven ineffective and irrational regarding less stringent objectives – conflicts with Articles 3, 97, and 117, first paragraph, of the Constitution, also in light of the more stringent obligations imposed by Directive 2024/2881/EU, especially for the Po Valley.

The provision would therefore be constitutionally illegitimate to the extent that it does not impose upon the State the exercise of ordinary and direct legislative competence in cases – such as in the Po Valley – where atmospheric pollution requires ultra-regional interventions.

2.– On September 30, 2025, the President of the Council of Ministers, represented and defended by the State Attorney General's Office (Avvocatura generale dello Stato), entered an appearance in all proceedings with separate acts of identical tenor, requesting that the raised questions be declared inadmissible or ungrounded.

2.1.– Prior to illustrating the inadmissibility of the raised questions, the President of the Council of Ministers sets forth certain introductory premises reconstructing the regulatory framework and the grounds of censure deduced in the appeals.

2.2.– As a preliminary matter, state defense raises an objection of overall inadmissibility of the three appeals for lack of so-called "redundancy" (ridondanza), and thus of legal interest to act (reference is made to the judgments of this Court No. 278 and No. 52 of 2010, No. 50 of 2008, No. 285 of 2005, and the case law cited therein).

In particular, attention is drawn to what this Court highlighted in judgment No. 116 of 2006, according to which regions «may assert the conflict with constitutional norms other than those attributing legislative competence only if it results in an exclusion or limitation of regional powers, without complaints of illogicality or violation of constitutional principles that do not result in an infringement of regional competence spheres being relevant» (reference is also made to the judgments of this Court No. 139 of 2024; No. 261, No. 170, No. 154, No. 114, No. 75, and No. 13 of 2017; No. 16 of 2010; No. 107 of 2009; No. 216 and No. 63 of 2008).

The appearance entry argues that, in the present case, the challenged provision is limited to establishing principles and guiding criteria for the transposition of Directive 2024/2881/EU on air quality and that, therefore, this falls within the exclusive legislative competence of the State in environmental protection (Article 117, second paragraph, letter s, of the Constitution), such that no regional legislative competence is infringed.

In the view of state defense, the appellants, while not contesting the exclusive competence of the State, complain of violations of constitutional parameters other than those attributing legislative competence, without clearly indicating which of their legislative competences have been affected and in what manner.

Consequently, the appeals would be manifestly inadmissible for failure to demonstrate the "redundancy defect" and a concrete interest. Indeed, a compression of regional functions cannot be configured; on the contrary, the State recognized them in continuity with Legislative Decree No. 155 of 2010.

Essentially, the appellants do not contest an infringement of their constitutionally guaranteed competences, but unreasonably complain of the allocation of administrative functions by the State connected to the uncontested exclusive legislative power pursuant to Article 117, second paragraph, letter s), of the Constitution. The appeals would thus fall outside the model of Article 127 of the Constitution, pursuant to which regions may only denounce the infringement of their constitutionally guaranteed «sphere of competence».

State defense doubts the very legal admissibility of the actions brought by the Regions, which appear designed to achieve a utility – exclusion from an administrative function ordinarily and legitimately assigned by the state legislature in the exercise of its own exclusive legislative competence – that seems to find no specific protection in the constitutional order.

2.3.– Having premised this, regarding the first ground of the Region of Lombardy's appeal, which contests the failure to obtain the opinion of the State-Regions Conference during the approval of Article 12 of Law No. 91 of 2025, state defense preliminarily raises an objection of inadmissibility for lack of "redundancy" and absence of interest to appeal.

More specifically, the reasons why the failure to issue the opinion on the amendment concerning the transposition of Directive 2024/2881/EU infringed the Region's legislative competences remain incomprehensible, since the challenged provision intervenes in a sector such as «environmental protection, ecosystem, and cultural heritage» exclusively attributable to state legislative competence, pursuant to Article 117, second paragraph, letter s), of the Constitution.

Furthermore, state defense highlights that the Region of Lombardy did not even specifically indicate which regional competences the contested provision interferes with, limiting itself, in essence, to reproducing or paraphrasing the text of Article 12 of Law No. 91 of 2025.

On the merits, the first ground of the Region of Lombardy's appeal is manifestly ungrounded.

Contrary to the appellant's assertions, the opinion of the State-Regions Conference was actually obtained in full compliance with the rules governing the transposition and implementation phase of European Union law (reference is made to Articles 2 and 5 of Legislative Decree No. 281 of 1997 and this Court's judgment No. 401 of 2007).

In the present case, on October 17, 2024, the State-Regions Conference expressed its opinion, pursuant to Article 5, paragraph 1, letter b), and Article 2, paragraph 5, of Legislative Decree No. 281 of 1997, on the bill (XIX Legislature, A.S. 1258), bearing «Delegation to the Government for the transposition of European directives and the implementation of other European Union acts - European Delegation Law 2024». Therefore, the regulatory dictate was complied with, as it does not require the Conference's opinion on every amendment introduced during legislative activity.

The appearance entry specifies that, in any event, even if it were to be considered that the Conference should have expressed its opinion also on governmental amendment No. 6.0.400 (concerning the transposition of Directive 2024/2881/EU), submitted during the parliamentary examination of the bill in question, the absence of such opinion would not in any case determine the constitutional illegitimacy of the challenged provision, since a procedural flaw deriving from the violation of ordinary law (namely Legislative Decree No. 281 of 1997) rather than a constitutional provision would be at issue (reference is made to this Court's judgment No. 237 of 2017).

Nor, according to state defense, can it be argued that the failure to obtain the opinion constitutes a violation of the principle of loyal cooperation derivable from Articles 5 and 120 of the Constitution, since consolidated case law of this Court holds that it «does not apply to the legislative procedure» (reference is made to judgments No. 192 and No. 63 of 2024, No. 192 of 2017, No. 251 and No. 65 of 2016, No. 250 of 2015, No. 401 of 2007, No. 272 of 2005, and No. 437 of 2001).

The appearance entry also challenges the reference to this Court's judgment No. 72 of 2019, which concerned the different case of the downstream omission of the obligation to adopt the implementing decree following an agreement (intesa) to be reached within the Permanent Conference for the Relations between the State, the Regions, and the Autonomous Provinces of Trento and Bolzano. Moreover, that judgment admitted recourse to the criterion of prevalence.

2.4.– Regarding the second ground of the Region of Lombardy's appeal and the third ground of the appeals of the Regions of Piedmont and Veneto, which challenge Article 12, paragraph 2, of Law No. 91 of 2025 for providing that the legislative decrees transposing Directive 2024/2881/EU are adopted upon receiving the opinion of the Unified Conference rather than prior agreement (intesa), state defense preliminarily raises an objection of inadmissibility: as to the Region of Lombardy's appeal, for lack of "redundancy" and absence of interest to appeal; as to the appeals of the Regions of Piedmont and Veneto, for «intrinsic contradictoriness».

In particular, the respondent argues that the Regions of Piedmont and Veneto – while acknowledging, in substance, the prevalence of the matter «environmental protection» of exclusive state legislative competence over regional competence matters – would then contradictorily assert that the case at hand involves an inextricable intertwining of competences, which would have required the provision of an agreement (intesa) instead of an opinion at the time of enacting the legislative decrees. The contradictory reasoning of the censure would therefore imply failure to satisfy the burden of exactly identifying the brought question of constitutional legitimacy (reference is made to this Court's judgment No. 39 of 2014).

It is also observed that the appellants apodictically deduced that the matter regulated by the challenged legislation involves state and regional legislative competences characterized by an inextricable intertwining, without however specifically indicating which regional attributions would be involved and for what reason, with respect to such attributions, the exclusive legislative competence of the State in environmental and ecosystem protection pursuant to Article 117, second paragraph, letter s), of the Constitution would not be prevalent anyway.

On the merits, these grounds of appeal would also be manifestly ungrounded.

According to the President of the Council of Ministers, constitutional case law has consistently affirmed that the principle of loyal cooperation «"does not apply to the legislative procedure"», while recognizing that it finds application within the scope of legislative delegation (reference is made to the judgments of this Court No. 63 of 2024, No. 192 of 2017, No. 251 and No. 65 of 2016, No. 250 of 2015, No. 401 of 2007, No. 272 of 2005, and No. 437 of 2001).

More specifically, judgment No. 251 of 2016 clarified that prior agreement (intesa) is required exclusively in cases where the delegation invests areas characterized by an inextricable intertwining of state and regional legislative competences, without a prevalent state competence being identifiable. Only in such hypotheses does a mere opinion prove insufficient, rendering a more incisive collaborative module necessary.

State defense also recalls this Court's judgment No. 72 of 2019, according to which the criterion of prevalence must be evaluated from both a qualitative and a quantitative profile, arguing that, in the present case, the core essence of the regulation is attributable to the matter «environmental and ecosystem protection», reserved to the exclusive legislative competence of the State pursuant to Article 117, second paragraph, letter s), of the Constitution.

From this perspective, the objective pursued by the state legislature is primarily environmental protection, whereas the additional sectors involved have an accessory and serving function. Nor, in the State Attorney General's opinion, does the transversal nature of environmental matters (reference is made to this Court's judgment No. 16 of 2024) exclude the prevalence of state competence, since an assessment in concreto must be carried out; on the contrary, such transversality confirms the need to ensure uniform standards throughout the national territory, which can be guaranteed solely by the State (reference is made to the judgments of this Court No. 198 of 2018 and No. 278 of 2012).

Therefore, in cases such as the one under examination, constitutional case law considers the opinion of the State-Regions Conference an adequate instrument of loyal cooperation, reserving recourse to an agreement (intesa) solely to hypotheses where a prevalent state legislative competence is not identifiable or where the delegation directly impacts regional organization.

The President of the Council of Ministers lastly represents that the regulatory framework introduced by the state legislature would in any case guarantee adequate regional involvement, since the procedure for enacting legislative decrees provides for the necessity of acquiring the opinion of the State-Regions Conference; downstream of the legislative intervention, moreover, the regions are in any case attributed the power to define the contents of measures «in agreements signed by the interested regional authorities and all state authorities competent over the relevant emission sectors» (reference is made to Article 12, paragraph 1, letter b, of Law No. 91 of 2025).

2.5.– Regarding the third ground of the Region of Lombardy's appeal, which contests the violation of Article 117, third and fourth paragraphs, of the Constitution, on the grounds that Article 12 of Law No. 91 of 2025, although presented as a provision pertaining to environmental protection, would actually significantly impact areas of regional legislative competence, both concurrent and residual, state defense preliminarily raises an objection of manifest inadmissibility for generality and for apodictic and tautological formulation (reference is made to this Court's judgments No. 231 of 2017 and No. 104 of 2014, which refers to judgment No. 272 of 2013).

The constitutional parameter whose violation is alleged, namely Article 117, third and fourth paragraphs, of the Constitution, is merely invoked, but lacks even a concise illustrative section of the reasons for the complained violation, as the Region limited itself to asserting that it suffered an infringement of its legislative competences because the challenged provision will have a "direct impact" on them.

On the merits, the ground is in any case manifestly ungrounded.

Article 12 of Law No. 91 of 2025 stands in continuity with the model of Legislative Decree No. 155 of 2010, implementing Directive 2008/50/EC, which already assigns to the regions the task of drafting regional air quality plans (reference is made to Article 9 of Legislative Decree No. 155 of 2010) and to the State coordination and supplementary intervention functions (reference is made to Article 9, paragraphs 9 and 10, and Article 20 of Legislative Decree No. 155 of 2010). Article 12 of Law No. 91 of 2025 does nothing more than provide for forms of "empowerment" (responsabilizzazione) of all actors involved and instruments of linkage and coordination.

The state legislature established delegation criteria that, in the distribution of competences, prioritize synergy, integration, and coordination among institutional subjects, providing specific organizational and procedural instruments. Primarily, air quality remediation measures are entrusted to regional and local authorities, barring national interventions in foreseen cases. Such an arrangement, to be better defined by the delegated legislature, is consistent with the principle of subsidiarity, which allocates functions to the level of government closest to citizens, unless effectiveness requirements demand higher levels.

The delegation provision, therefore, does not deprive the regions of any function, but confirms their ordinary role in air quality planning.

Finally, it is highlighted that the appellant generically contests the forms of "synergy" provided for by Article 12 of Law No. 91 of 2025, deducing that «the one-way synergy conceived by Article 12 of Law No. 91/2025 will have a direct impact on the planning of other regional domains (health protection, transport, energy)», without specifying – confirming the obscurity of the censure – what it means by "one-way synergy"; nor is it understood for what reasons the challenged provisions are deemed constitutionally illegitimate and in what sense the realization of synergy is hoped for.

2.6.– Regarding the fourth ground of the Region of Lombardy's appeal, which contests the violation of Articles 3, 97, and 118 of the Constitution, state defense preliminarily raises an objection of inadmissibility (subsequently specifying that it is «manifest[…]») for lack of "redundancy" and consequent absence of interest to act, since the Region, in a singular manner, complains of an infringement of its attributions not because the State subtracted competences belonging to it, but because excessive competences were entrusted to it, for the exercise of which the appellant would be inadequate.

Essentially, the Region censures not an impairment of its legislative competences, but, on the contrary, the allocation of administrative functions in its favor. The fourth ground, as framed by the appellant, is therefore manifestly inadmissible, as no «infringement of regional competence spheres» is found and no «compression» of regional powers and attributions emerges (reference is made to this Court's judgment No. 63 of 2008).

According to state defense, even assuming the profile of so-called "redundancy" abstractly exists, the ground of appeal would in any case be inadmissible for lack of interest to act, as the legislative delegation is not in itself capable of causing any current and concrete infringement of regional prerogatives (reference is made to the judgments of this Court No. 234 of 2013, No. 278 of 2010, and No. 224 of 1990).

Article 12 of Law No. 91 of 2025 does not possess a sufficient degree of determinacy to warrant the conclusion that a current and immediate infringement of constitutionally guaranteed regional legislative competences derives therefrom. Indeed, it will be up to the delegated legislature to introduce mechanisms ensuring synergy between actions relating to the remediation of ambient air quality and actions relating to sectors affecting major emission sources, providing the necessary integration and coordination measures.

On the merits, the fourth ground of appeal is also manifestly ungrounded.

It is stated that, according to the consolidated orientation of this Court, in matters attributed by Article 117, second paragraph, of the Constitution to the exclusive legislative competence of the State, choices concerning the allocation of related administrative functions are also reserved to the state legislature. Such choices – it is added – are subject to review only in the case of manifest unreasonableness, which was not argued by the Region and in any case cannot be discerned according to state defense (reference is made to the judgments of this Court No. 151 of 2024 and No. 189 of 2021).

For completeness, the President of the Council of Ministers states that the assessment allocating administrative functions to the regions in the present case is in any case fully respectful of Article 118, first paragraph, of the Constitution and, therefore, of the principles of subsidiarity, differentiation, and adequacy (reference is made to this Court's judgment No. 192 of 2024).

According to state defense, in the present case, the attribution of administrative functions to the regions is adequate, considering the nature of the activities and the territorial context. Although environmental protection is a matter of state legislative competence, it has a transversal character and may interfere with regional competences (reference is made to this Court's judgment No. 16 of 2024), which renders it reasonable to entrust connected administrative functions to the regions.

The challenged provision respects the principles of subsidiarity, differentiation, and adequacy by providing that measures for air quality improvement are ordinarily adopted at the regional and local levels, contemplating state interventions only subsidiarily. Such administrative measures (emission limitations, incentives, transport and mobility interventions, etc.) are strictly linked to territorial specificities and local planning and, therefore, should be managed primarily at the regional level.

It is therefore incorrect to argue that these competences should be allocated primarily and directly to the State, which nonetheless maintains a central role of coordination and supplementary intervention, already provided for by Legislative Decree No. 155 of 2010.

Regarding the particularity of the Po Valley, which would determine the impossibility of achieving, at the regional level, initiatives adequate to attain the purpose established by the European Union, state defense observes that precisely in that area «multilevel governance (State-Regions program agreements of 2013, 2017, and 2019 and now the national plan 2025-2027)» has developed, demonstrating how the problem is addressed not through a generalized centralization of competences in the State, but through synergistic, coordinated, and integrated action among different institutional levels.

Moreover, Article 12, paragraph 1, letter b), of Law No. 91 of 2025 itself provides, in compliance with the principle of vertical subsidiarity, for a central and significant role of the State regarding air quality.

2.7.– Regarding the fifth and final ground of the Region of Lombardy's appeal and the fourth ground of the appeals of the Regions of Piedmont and Veneto, which contest the constitutional illegitimacy of Article 12, paragraph 3, of Law No. 91 of 2025 to the extent that it establishes that its implementation must not entail new or greater burdens on public finance and that competent administrations must meet the related obligations with resources available under current legislation, state defense preliminarily contests its inadmissibility.

More specifically, the appellants fail to clarify what the impact of the challenged provisions is on their financial autonomy and, consequently, the consistency of the infringement inflicted upon their competences (reference is made to the judgments of this Court No. 63 of 2024, No. 83 of 2019, No. 251 of 2016, and No. 256 of 2014).

Furthermore, the Regions generically alleged the asserted insufficiency of resources available to them to face the attributed competences, without indicating either currently available and deployable resources or any greater resources deemed necessary.

The appeals are also deficient because the complained violations of regional financial autonomy are not substantiated by an adequate comprehensive analysis of regional budgets (reference is made to the judgments of this Court No. 220 of 2021 and No. 83 of 2019).

State defense also asserts that the Regions complain of the insufficiency of resources for functions attributed to them by future delegated decrees on air quality, putting forward an inadmissible censure: the decrees have not yet been enacted, so it is not possible to know their contents and concrete burdens. The grievances should therefore eventually be directed against the legislative decrees, not against the delegation law, which does not produce an immediate and current infringement.

On the merits, the grounds of appeal are in any case manifestly ungrounded.

First of all, the censure concerning the alleged violation of Article 81, third paragraph, of the Constitution is ictu oculi devoid of merit. This constitutional parameter establishes that «[e]very law entailing new or greater burdens shall provide for the means to cover them» and, in the present case, in paragraph 3 of Article 12 of Law No. 91 of 2025, the state legislature expressly provided for a financial invariance clause. The challenged provision aims precisely at ensuring compliance with the invoked parameter, avoiding unfinanced expenditures.

Planning, coordination, and monitoring activities already fall within the ordinary functions of the regions and do not require additional resources.

State defense further highlights that the delegated legislature may in any case modulate interventions by relating them to available means, valuing coordination and existing resources. Moreover, the financial invariance clause does not transfer burdens onto the regions, but binds all administrations to operate with existing resources, without violating the principle of loyal cooperation (reference is made to this Court's judgment No. 82 of 2023).

2.8.– Regarding the first ground of the appeals of the Regions of Piedmont and Veneto, which deduces the constitutional illegitimacy of Article 12, paragraph 1, letter b), of Law No. 91 of 2025, to the extent that it attributes to the regions primary responsibility for the adoption of regional air quality plans, reserving to the State a merely subsidiary or complementary role, state defense preliminarily contests its inadmissibility for lack of "redundancy" and consequent absence of interest to act, since the Regions, in a very singular manner, complain of an infringement of their attributions not because the State subtracted competences belonging to them, but because excessive competences were entrusted to them, for the exercise of which the appellant Regions would be inadequate. Essentially, the Regions censure not an impairment of their legislative competences, but, on the contrary, the allocation of administrative functions in their favor.

The defect of so-called "redundancy" is even more evident with reference to Article 117, second paragraph, letter s), of the Constitution, since, according to constitutional case law, a region cannot «deduce, as the foundation of its own hypothetical title of intervention, a primary competence reserved exclusively to the State, not even when it intertwines with distinct competences of secure regional belonging» (reference is made to this Court's judgment No. 56 of 2020).

In any event, the aforementioned "redundancy" profile would be inadmissible for lack of interest to act, as the legislative delegation is not in itself capable of causing any current and concrete infringement of regional prerogatives (reference is made to the judgments of this Court No. 234 of 2013 and No. 224 of 1990).

The challenged provision, which in the appellants' opinion outlines an inadequate allocation of competences, does not possess a sufficient degree of determinacy to warrant the conclusion that a current and immediate infringement of constitutionally guaranteed regional legislative competences derives therefrom, as it will be up to the delegated legislature to introduce, inter alia, mechanisms ensuring synergy between actions relating to the remediation of ambient air quality and actions relating to sectors affecting major emission sources and other necessary integration and coordination measures.

On the merits, state defense deduces the manifest ungroundedness of the questions based on the same arguments already illustrated with reference to the fourth ground of the Region of Lombardy's appeal.

2.9.– Regarding the second ground of the appeals of the Regions of Piedmont and Veneto, which contests the constitutional illegitimacy of Article 12, paragraph 1, letter b), of Law No. 91 of 2025 under a different profile, namely for violation of Articles 3, 97, and 117, first paragraph, of the Constitution, state defense preliminarily contests its inadmissibility for the same reasons already highlighted in relation to the first ground of appeal.

As to the parameter of Article 117, first paragraph, of the Constitution, the ground would in any case be manifestly inadmissible as it fails to elucidate why the potential violation of such parameter results in a limitation of the regions' constitutional attributions (reference is made to the judgments of this Court No. 244 of 2012 and No. 225 of 2019). Furthermore, the interposed supranational norms allegedly violated are not specified either (reference is made to the judgments of this Court No. 249 of 2019, No. 201 of 2017, and No. 156 of 2016) and the conflict is invoked in an absolutely generic manner (reference is made to the judgments of this Court No. 199 of 2014 and No. 311 of 2013).

In relation, moreover, to the parameter represented by Article 117, third and fourth paragraphs, of the Constitution, state defense highlights that constitutional case law links so-called redundancy to the existence of «regional competences susceptible of being indirectly infringed by the challenged legislation [...]» (reference is made to this Court's judgment No. 145 of 2016), whereas the Regions limited themselves to representing a mere risk of having to exercise their attributions in compliance with allegedly illegitimate legislation. This configures a purely hypothetical, unproven event of currently merely factual relevance, and is therefore unsuitable and insufficient to establish the interest to act via the remedy provided by Article 127, second paragraph, of the Constitution.

On the merits, the second ground of the appeals is in any case manifestly ungrounded.

State defense reiterates that the allocation outlined by Article 12, paragraph 1, letter b), of Law No. 91 of 2025 is not unreasonable, constituting direct application of the principle of subsidiarity, pursuant to which administrative functions belong to the level of government closest to citizens, unless, for reasons of «scale or effectiveness», they must be exercised at higher levels.

Moreover, the principle of sound administration cannot be deemed infringed in any way, since the challenged provision provides, alongside ordinary allocation, instruments of integration and coordination among different levels of government ensuring coherence and efficiency to administrative action, as demonstrated by the experience of program agreements and the national air quality plan approved in 2025.

The argument of an indirect infringement of regional competences is also ungrounded: the delegation does not deprive the regions of functions, but confirms their role in drafting air quality plans, leaving concurrent legislative competences intact, to be exercised consistently with European Union objectives and in loyal cooperation with the State. There is therefore no violation of Articles 117 and 118 of the Constitution.

Finally, the argument that the regions would be forced to adopt acts vitiated by derived illegitimacy is also ungrounded: since the allocation of competences provided by the delegating legislature complies with the Constitution, the very prerequisite of the flaw is lacking.

2.10.– On April 3, 2026, in the proceedings registered under number 34 of the 2025 appeal registry, a brief was filed by the Region of Lombardy, reiterating what was already deduced in the introductory act.

2.11.– On April 14, 2026, in all proceedings, briefs were filed by the President of the Council of Ministers, reiterating what was already deduced in the appearance entry and insisting on the declaration of inadmissibility of the appeals and, in any event, on their dismissal.

2.12.– Finally, on April 15, 2026, in the proceedings registered under numbers 35 and 36 of the 2025 appeal registry, briefs were filed by the Region of Piedmont and the Region of Veneto, replying to the objections and arguments set forth in the President of the Council of Ministers' appearance entry, asserting their erroneousness and ungroundedness.

More specifically, regarding the objection of inadmissibility raised by state defense with reference to all appeals, the two Regions argue, inter alia, that principal constitutional review proceedings are configured as a jurisdictional instrument for protecting not only legislative attributions, but all others (regulatory, administrative, and financial) that are relevant within the spheres of regional competence guaranteed by the Constitution.

They also argue that the «infringement of their spheres of competence», to which Article 127 of the Constitution links a region's standing to bring principal proceedings, is to be understood as a violation of the constitutional norms delimiting such competences, so that an infringement may be configured both when attributions are unduly subtracted or limited to the detriment of the region and, conversely, when functions constitutionally reserved to other entities are attributed to it. Such a profile, however, would be relevant only with reference to one of the grounds of appeal.

Considerato in diritto

3.− The Region of Lombardy, by an appeal registered under No. 34 reg. ric. of 2025, and the Regions of Piedmont and Veneto, by appeals of substantially overlapping content registered respectively under numbers 35 and 36 reg. ric. of 2025, brought multiple questions of constitutional legitimacy regarding Article 12 of Law No. 91 of 2025, bearing delegation to the Government for the transposition of Directive (EU) 2024/2881 on air quality.

The censures formulated in the appeals are articulated into multiple orders of grievances.

3.1.− By the first ground of its appeal, the Region of Lombardy complains of the violation of the principle of loyal cooperation under Articles 120, second paragraph, and 5 of the Constitution, because the approval of the challenged provision occurred without the necessary involvement of the State-Regions Conference.

3.2.− By the second ground of the appeal, also shared by the Region of Piedmont and the Region of Veneto in their third ground of appeal, the Region of Lombardy complains, with particular reference to paragraph 2 of the challenged Article 12, once again of the violation of the principle of loyal cooperation, but with reference to the provision for a mere opinion of the Unified Conference, rather than an agreement (intesa), prior to the adoption of legislative decrees implementing the delegation.

3.3.− By the third ground of the appeal, it argues that Article 12 of Law No. 91 of 2025 is constitutionally illegitimate for violation of Article 117, third and fourth paragraphs, of the Constitution and of the principle of loyal cooperation, also as a «consequence of what has been set forth in the preceding grounds, with reference to the violation of the principle of loyal cooperation».

More specifically, the appeal contests «the concept of synergy, referred to in Article 12», a synergy conceived in a one-way manner.

3.4.− By the fourth ground of the appeal, it alleges the constitutional illegitimacy of the challenged provision also for violation of Article 3 of the Constitution, as regards reasonableness, Article 97 of the Constitution, as regards sound administration, and Article 118 of the Constitution, as regards adequacy.

The challenged provision, indeed, fails to provide adequate coordination instruments or shared participatory modalities, resulting in a fragmented system where the State and regions operate on parallel planes. This would be inefficient and unsuited to guarantee the achievement of European Union objectives regarding air quality.

3.5.− By the fifth and final ground of the appeal, it contests the constitutional legitimacy of Article 12, paragraph 3, of Law No. 91 of 2025, for violation of Articles 81, 97, and 119 (cursory reference is also made to Articles 3 and 118 of the Constitution) of the Constitution, as it mandates the exercise of new functions without providing adequate financial coverage and infringes regional prerogatives and the principles of public finance coordination, sound administration, and balanced budget.

Censures analogous to this are also proposed by the Regions of Piedmont and Veneto by the fourth ground of their appeals.

3.6.− The same Regions of Piedmont and Veneto, by the first ground of their appeals, additionally deduce the constitutional illegitimacy of Article 12, paragraph 1, letter b), of Law No. 91 of 2025, for violation of Article 117, second paragraph, letter s), of the Constitution, with reference to the matter «environmental and ecosystem protection», as well as Article 118, first paragraph, of the Constitution and the principles of subsidiarity, differentiation, and adequacy contemplated therein, for the correct allocation of administrative functions among the territorial entities of the Republic. The appellants consider that the challenged provision attributes tasks to the regions for the fulfillment of which they are structurally inadequate, specifically in complex territorial contexts such as the Po Valley, characterized by unfavorable orographical and climatic conditions.

3.7.− By the second ground of their appeals, the Regions of Piedmont and Veneto deduce the constitutional illegitimacy of Article 12, paragraph 1, letter b), of Law No. 91 of 2025 also for violation of Articles 3, 97, and 117, first paragraph, of the Constitution, in relation to Directive 2024/2881/EU, with the concomitant indirect infringement of regional legislative and administrative competences under Articles 117, third and fourth paragraphs, and 118 of the Constitution. Indeed, both the regions of the Po Valley and the State would be prevented from achieving the objectives of Directive 2024/2881/EU.

4.– On September 30, 2025, the President of the Council of Ministers, represented and defended by the State Attorney General's Office, entered an appearance in all proceedings with separate acts of identical tenor, requesting that the promoted questions be declared inadmissible or ungrounded.

5.– Preliminarily, it must be noted that the introductory acts are partially overlapping.

More specifically, the appeals brought respectively by the Region of Piedmont and the Region of Veneto (reg. ric. No. 35 and No. 36 of 2025) have totally overlapping content, whereas the appeal of the Region of Lombardy (reg. ric. No. 34 of 2025) exhibits only partially coincident content: only two of the grounds deduced therein (the second and the fifth) coincide, in substance, with two of the grounds deduced also by the Regions of Piedmont and Veneto (the third and the fourth). These are the grounds whereby the Regions, albeit with varying formulation, declination, and invocation of pertinent parameters, contest, on the one hand, the violation of the principle of loyal cooperation, as the provision mandates that the legislative decrees provided for in paragraph 1 be adopted upon receiving the opinion of the Unified Conference referred to in Article 8 of Legislative Decree No. 281 of 1997, rather than upon prior agreement (intesa); on the other hand, the lack of adequate financial coverage, with consequent violation of the principles of public finance coordination, sound administration, and balanced budget, with relative infringement of regional prerogatives.

Joinder of the proceedings must therefore be ordered so that they may be decided by a single judgment, as certain questions of constitutional legitimacy have as their object the same norms, put forward analogous censures, and invoke partially coincident parameters.

6.– Before proceeding to examine the questions, it is useful to briefly recall European legislation concerning air quality.

Directive 2024/2881/EU, adopted on the basis of Article 192, paragraph 1, TFEU in environmental matters, unifies and replaces Directives 2008/50/EC (already recalled in the narrative) and 2004/107/EC of December 15, 2004 (concerning arsenic, cadmium, mercury, nickel, and polycyclic aromatic hydrocarbons in ambient air), both of the European Parliament and of the Council, which will be repealed with effect from December 12, 2026 (Article 31, paragraph 1, of Directive 2024/2881/EU).

Directives 2008/50/EC and 2004/107/EC were transposed into Italy, respectively, by Legislative Decree No. 155 of 2010, Legislative Decree No. 250 of December 24, 2012 (Amendments and additions to Legislative Decree No. 155 of August 13, 2010, bearing implementation of Directive 2008/50/EC on ambient air quality and cleaner air for Europe), and Legislative Decree No. 152 of August 3, 2007 (Implementation of Directive 2004/107/EC relating to arsenic, cadmium, mercury, nickel, and polycyclic aromatic hydrocarbons in ambient air).

The transposition of Directive 2024/2881/EU was instead provided for by Article 12 of Law No. 91 of 2025.

The objective of the directive is to achieve "zero pollution" by 2050, progressively improving air quality to levels not harmful «to human health, natural ecosystems, and biodiversity» (Article 1). To this end, following the model of previous directives, it establishes rules on: air quality objectives, assessment methods, monitoring, and maintenance or improvement measures. The parameters – indicated in Annex I – (limit values, target values, average exposure reduction obligations, average exposure concentration objectives, critical levels, alert thresholds, information thresholds, and long-term objectives) are updated periodically, in line with World Health Organization (WHO) recommendations (Article 1, paragraph 2).

The directive also provides that «[i]n all zones classified as above the assessment thresholds established for pollutants referred to in Article 7» – pursuant to which «[t]he assessment thresholds indicated in Annex II apply to sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter (PM10 and PM2.5), benzene, carbon monoxide, arsenic, cadmium, lead, nickel, benzo(a)pyrene and ozone in ambient air» (Article 7, paragraph 1) – «ambient air quality shall be assessed by means of fixed measurements» (Article 8, paragraph 2), confirms the zoning of territory (Article 6), and introduces new monitoring obligations, including "supersites" for larger Member States such as Italy (Article 10).

The directive establishes that by December 11, 2026 (the deadline for its transposition), the limit values to be respected are similar to those provided by previous directives; it also sets stricter limits to be achieved by January 1, 2030 (in particular for PM2.5, PM10, and NO2), closer to (though still exceeding) WHO standards.

Pursuant to Article 18 of the directive, extensions of deadlines are permitted where justifying reasons exist (deadlines of January 1, 2035, and January 1, 2040, are provided). Member States must also adopt air quality plans for zones where pollutant levels in «ambient air» exceed any limit value or target value set in Annex I, Section 1, of the directive (Article 19). Furthermore, if in certain zones there is a risk that pollutant levels will exceed one or more alert thresholds referred to in Annex I, Section 4, of the directive, Member States must also adopt short-term action plans containing indications on emergency measures (Article 20).

Finally, the directive introduces important innovations regarding access to justice and compensation for damage to human health.

In particular, Article 28, paragraph 1, provides that Member States shall ensure that natural persons whose health has suffered damage as a result of a violation of national transposition rules concerning air quality plans and "roadmaps" (referred to in Article 19, paragraphs 1 to 5) or short-term action plans (referred to in Article 20, paragraphs 1 and 2) – which violation has been committed intentionally or negligently by the competent authorities – have the right to claim and obtain compensation.

Having thus reconstructed the essential features of European legislation relating to air quality, we may proceed to examine the questions submitted to this Court.

7.– It is appropriate to begin with preliminary questions.

7.1.– The State Attorney General's Office raises first an objection of inadmissibility (subsequently qualified as «manifest[…]») with reference to all introductory appeals of the present proceedings.

According to state defense, the Regions do not allege the violation of constitutional norms attributing legislative competences and, therefore, the case law of this Court applies, according to which regions «may assert the conflict with constitutional norms other than those attributing legislative competence only if it results in an exclusion or limitation of regional powers, without complaints of illogicality or violation of constitutional principles that do not result in an infringement of regional competence spheres being relevant» (judgment No. 116 of 2006; lately, in the same sense, judgment No. 139 of 2024).

The appearance entry argues that, in the present case, the challenged provision is limited to establishing principles and guiding criteria for the transposition of Directive 2024/2881/EU on air quality and that, therefore, it falls within the exclusive legislative competence of the State in environmental protection (Article 117, second paragraph, letter s, of the Constitution); such that no regional legislative competence can be deemed infringed.

In the view of state defense, the appellants, while not contesting the exclusive legislative competence of the State, complain of violations of constitutional parameters other than those attributing legislative competences to the regions, without clearly indicating which legislative competences – instead – have been affected and in manner. Indeed, there is no compression of regional prerogatives; rather, these are functions that the State attributed to the regions in continuity with Legislative Decree No. 155 of 2010.

7.2.– An objection of inadmissibility for lack of "redundancy" and consequent absence of interest to act was also proposed with more specific reference to the first and second grounds of the Region of Lombardy's appeal and the first and second grounds of the appeals of the Regions of Piedmont and Veneto.

Regarding the first ground of the Region of Lombardy's appeal, state defense highlights, inter alia, that the Region did not even specifically indicate which regional competences the contested provision interferes with, limiting itself, in substance, to reproducing or paraphrasing the text of Article 12 of Law No. 91 of 2025.

Regarding the first and second grounds of the appeals of the Regions of Piedmont and Veneto, it is argued that they complain of a singular infringement of constitutional prerogatives not by reason of the subtraction of competences belonging to them, but of the entrustment of excessive competences, to the exercise of which the appellant regions would be inadequate. Essentially, what was complained of was not an impairment of regional legislative competences, but rather the allocation of administrative functions from the State to the regions.

The defect of so-called "redundancy" would be even more evident with reference to Article 117, second paragraph, letter s), of the Constitution, since, according to this Court's case law, a region cannot «deduce, as the foundation of its own hypothetical title of intervention, a primary competence reserved exclusively to the State, not even when it intertwines with distinct competences of secure regional belonging» (reference is made to this Court's judgment No. 56 of 2020).

7.3.– Essentially, with the general objection and the more specific one, state defense, alleging a lack of "redundancy", objects to the inadmissibility of the challenges on the grounds that: a) the allocation, and not the subtraction, of a competence is complained of; b) the competence whose infringement is complained of is not legislative.

None of these exception profiles can be upheld.

The constant case law of this Court considers admissible «questions of constitutional legitimacy that a region, within the framework of principal proceedings, raises by reference to parameters other than those governing the distribution of competences between the State and the regions, provided that the spheres of regional legislative competence indirectly affected by the state legislation are clearly identified and the redundancy flaw is adequately illustrated» (judgment No. 139 of 2024, which refers to judgment No. 40 of 2022, point 2.4 of the Considerato in diritto, emphasis added; on this point, also judgments No. 56 of 2020, No. 261, No. 231, No. 170, No. 154, No. 114, No. 75, and No. 13 of 2017, No. 251, No. 202, No. 145, and No. 68 of 2016, No. 104 of 2014, No. 236, No. 220, and No. 219 of 2013, No. 244 of 2012, No. 128 and No. 33 of 2011, No. 107 of 2009, No. 116 of 2006, and No. 285 of 2005), namely the profiles through which the complained flaws result in a violation of regional attributions.

Principal constitutional review proceedings are thus configured as an instrument for protecting legislative attributions not only directly, but also indirectly. Indeed, an indirect infringement of regional legislative competences is in re ipsa whenever the State detrimentally impacts any domain of regional competence (regulatory, administrative, and financial) guaranteed by the Constitution, since such an occurrence conditions regional primary law-making anyway.

Most importantly, Article 127, second paragraph, of the Constitution allows a region to act before this Court «when it deems that a law or an act having force of law of the State or of another Region infringes its sphere of competence». What matters, therefore, is solely the infringement of the «sphere of competence», which may occur regardless of the specific "type" of competence deemed compromised. Being, moreover, the spatial delimitation of a competence "sphere", the integrity of said sphere is relevant, and it is altered when its shape or dimension is modified. Consequently, the infringement legitimizing the challenge may well be configured not only when regional competences are unduly subtracted or limited, but also, conversely, when competences that do not belong to them and which the Constitution assigns to other entities are attributed to the regions.

This Court has also affirmed that «questions of constitutional legitimacy raised by Regions with reference to parameters unrelated to the distribution of state and regional competences are admissible upon the occurrence of two concomitant conditions: firstly, the appellant must identify the domains of regional competence – legislative, administrative, or financial – impacted by the state legislation, indicating the constitutional provisions upon which – precisely – its own indirectly infringed competences are founded [...]; and, secondly, this Court must deem that regional competences susceptible of being indirectly infringed by the challenged legislation exist [...]» (judgment No. 145 of 2016). This occurs when the state provision, although compliant with the constitutional distribution of competences, obliges Regions – in the exercise of their other normative, administrative, or financial attributions – to comply with a legislative discipline allegedly unconstitutional due to conflict with parameters extraneous to that distribution. All of this confirms both that the functions protectable in court by regions include those other than legislative ones, and that the complained infringement may also be merely indirect.

That being said, the appellant Regions generally complain of the fact that the State provided for the attribution to them of administrative functions, primarily of a planning character (in matters including health protection, national production, transport, and distribution of energy, territorial governance, agriculture, and local public transport), aimed at implementing the European directive on air quality, although they have already demonstrated inability to achieve the results provided therein (three infringement procedures are recalled: No. 2014/2147, No. 2015/2043, and No. 2020/2299).

According to the Regions, in light of the demonstrated inability to achieve European air quality objectives, such functions should have been placed upon the State.

Indeed, Section B of the Region of Lombardy's appeal is specifically dedicated to demonstrating «redundancy on regional competences»; the first ground of the appeals of the Regions of Piedmont and Veneto is aimed precisely at censuring the attribution of certain administrative air remediation functions to regional authorities.

The Regions, therefore, have indicated what recognized constitutional prerogatives of theirs were impacted by the challenged provisions. And that suffices, given that «Regions "are entitled to denounce only violations capable of repercussing their effects, directly and immediately, upon the constitutional prerogatives recognized to them by the Constitution. Hence it follows that within such a framework – characterized by the necessity that the initiative undertaken by the appellant Regions be objectively directed at achieving the utility proper, obviously, to the type of proceeding that may from time to time be relevant – the existence of the interest to act must be assessed, to be postulated only when it presents the characteristics of concreteness and currency, consisting in that direct and immediate utility that the acting party can obtain with the measure requested of the court" (judgments No. 107 of 2009 and No. 216 of 2008)» (judgment No. 170 of 2017).

Moreover, when the subject matter concerned by the regional appeal in principal proceedings is, as in the present case, environmental protection, the Court has affirmed that «[r]edundancy on such attributions [...] is not prevented but is correlated with the "transversal" nature of the matter to which the provision is primarily attributable, since, "given the breadth and complexity of themes pertaining to environmental protection, the principles and rules elaborated by the State in subiecta materia involve other legal goods, having as their object components or aspects of the environmental good, but concerning different legally protected interests within the scope of other legislative competences distributed according to the canons of Article 117 of the Constitution" [...], interests of which the regions are also bearers» (judgment No. 114 of 2017, which refers to judgment No. 278 of 2012).

In conclusion, since the Regions argue the impact of the challenged provision on their specific administrative competences of constitutional rank, the redundancy requirement is satisfied.

The rest pertains to the merits, since, as this Court has already affirmed: «[t]he question [...] at the conclusion of a review on the merits, might prove ungrounded with respect to competence parameters, but be deemed preliminarily admissible precisely due to its potential impact on the latter. Only if from the very framing of the appeal the irrelevance of the question with respect to regional competence domains emerges – independently of any evaluation on the ungroundedness of the censures – must the question be declared inadmissible» (judgment No. 220 of 2013, which refers to judgment No. 8 of 2013).

7.4.– The objection of inadmissibility for "intrinsic contradictoriness", raised by the State Attorney General's Office regarding the second ground of the Region of Lombardy's appeal, is also ungrounded.

This ground is indeed supported by sufficient arguments and reasoning capable of making the meaning of the censure understood.

7.5.– Likewise ungrounded are the objections of inadmissibility concerning the first and second grounds of the appeals of the Regions of Piedmont and Veneto, which put forward a lack of interest to act on the grounds that the delegation is not in itself capable of causing a current and concrete infringement of regional prerogatives.

State defense argues that challenged Article 12 of Law No. 91 of 2025 does not possess a sufficient degree of determinacy to warrant the conclusion that a current and immediate infringement of regional legislative competences derives therefrom. It is argued, instead, that such an infringement will occur, if at all, only upon the adoption of delegated legislative decrees, to which alone the concrete identification of modalities for implementing Directive 2024/2881/EU is entrusted.

In reality, the challenged provision nonetheless imposes constraints on the delegated legislature that are already sufficient by themselves to integrate the interest to appeal. And here too the question concerning the actual injuriousness of such constraints pertains to the merits.

7.6.– Finally, the objection of inadmissibility relating to the second ground of the appeals of the Regions of Piedmont and Veneto, with reference to the parameter of Article 117, first paragraph, of the Constitution on the grounds that the interposed supranational norms allegedly violated were not specified, is ungrounded.

Indeed, contrary to what state defense maintains, explicit reference is made in the appeals to «the much more severe and stringent obligations imposed by Directive (EU) 2024/2881».

7.7.– On the other hand, the objection of inadmissibility for generality of reasoning raised by the State Attorney General's Office with reference to the third ground of the Region of Lombardy's appeal must be upheld.

The appeal does not in fact allow understanding why the violation of Article 117, third and fourth paragraphs, of the Constitution would exist, as the appellant limits itself to asserting that «the one-way synergy conceived by Article 12 of Law No. 91/2025 will have a direct impact on the planning of other regional domains».

Furthermore, regarding the second ground of the appeals of the Regions of Piedmont and Veneto, the objection formulated by state defense with reference to the alleged violation of Article 117, first paragraph, of the Constitution, in relation to Directive 2024/2881/EU, must be upheld, given that such parameter is effectively invoked in an excessively generic manner.

On this point, also recently, this Court highlighted that «in principal proceedings the appellant bears the burden of identifying the challenged provisions and constitutional parameters whose violation it complains of and presenting reasoning that is not merely assertive, indicating the reasons for the conflict with the invoked parameters, through a – albeit concise – argumentative discussion on the merits in support of the censures» (judgment No. 82 of 2024; regarding this issue, among many, also judgments No. 136 and No. 28 of 2025, and No. 103 of 2024).

7.8.– Likewise, the objection of inadmissibility raised by the state defense regarding the fifth ground of the Region of Lombardy's appeal and the fourth ground of the appeals of the Regions of Piedmont and Veneto must be upheld.

State defense argues that the appellants failed to clarify either the impact of the challenged provisions on their financial autonomy or, consequently, the consistency of the infringement inflicted upon their respective competences. Furthermore, it asserts that the Regions generically alleged the asserted insufficiency of resources available to them to face newly attributed competences, without indicating either currently available and deployable resources or any greater resources deemed necessary.

The appeals would also be deficient because the complained violations of regional financial autonomy are not substantiated by an adequate comprehensive analysis of regional budgets.

State defense finally states that the Regions complain of the insufficiency of resources necessary to perform tasks not yet attributed to them and deriving, if anything, from (merely) future delegated legislative decrees on air quality, whose content is currently unknown. Hence the inadmissibility of the censures for lack of currency (whereas the currency requirement is of mandatory observance: see again judgment No. 170 of 2017).

These findings hit the mark. On the one hand, the appellants complain of the insufficiency of resources that will be necessary only for performing functions not yet conferred; on the other hand, they fail to specify with punctual analyticity what new functions would be assigned to them beyond those under Legislative Decree No. 155 of 2010.

Indeed, the activity of drafting air quality plans and monitoring functions already fall within the institutional and ordinary duties of regions, structurally not requiring additional resources. Moreover, the delegated legislature could well modulate further tasks taking available resources into account, valuing forms of inter-institutional coordination and the better utilization or distribution of pre-existing resources.

Faced with this, the grievance concerning the insufficiency of resources appears merely generic, so that the impact of the challenged provision on regional financial autonomy and the resulting infringement of the appellants' prerogatives are not clear.

Not only that. The Regions of Piedmont and Veneto complain that the general discipline provided for by Article 1, paragraph 3, of Law No. 91 of 2025 was derogated from, where it is provided that «[w]ithout prejudice to what is provided in Articles [...] 12, paragraph 3 [...], any expenses not contemplated by current laws and which do not concern the ordinary activity of state or regional administrations may be provided for in the legislative decrees referred to in paragraph 1 of this article, solely within the limits necessary for the fulfillment of obligations deriving from the exercise of the delegations referred to in the same paragraph 1. Related coverage, as well as the coverage of any reduced revenues deriving from the implementation of the delegations, where it is not possible to face them with funds already allocated to competent administrations, shall be provided by reducing the fund for the transposition of European legislation referred to in Article 41-bis of the aforementioned Law No. 234 of 2012. Should the endowment of said fund prove insufficient, legislative decrees from which new or greater burdens derive shall be enacted only after the entry into force of legislative provisions allocating the necessary financial resources, in compliance with Article 17, paragraph 2, of Law No. 196 of December 31, 2009». The exact scope of the provision in question, however, is not specified, nor is the operation of the coverage mechanism contemplated therein specified.

We are thus faced with a question of constitutional legitimacy of a state provision brought with reference (also in combination with other parameters) to Article 119 of the Constitution (note that the Region of Lombardy's appeal invokes Article 119 of the Constitution in its entirety, except for citing the text of its fifth paragraph at page 27, whereas the appeals proposed by the Regions of Piedmont and Veneto specifically invoke its fourth paragraph) without a complete demonstration of the scope and gravity of the financial effects complained of. This Court has affirmed that «[...] it is incumbent upon Regions, when claiming the illegitimacy of provisions providing for a reduction in exchequer transfers, that such reduction determines the insufficiency of financial means for fulfilling tasks belonging to them, and that failure to fulfill such burden entails the inadmissibility of the proposed question (ex plurimis, judgments No. 5 of 2018 and No. 192 of 2017)» (judgment No. 74 of 2019, which ruled for the inadmissibility of the censure; similarly, judgments No. 75 of 2018 and No. 36 of 2014). In the present case, it is not a question of reducing financial resources available to regions, but of the deemed conferral upon them of tasks considered additional. The appellants, nonetheless, omit to specify to what extent said alleged tasks would burden regional administration with greater costs and could not be tackled through a different organization of competent offices.

8.– Turning now to the merits, it is appropriate to begin with the first ground of the Region of Lombardy's appeal, where the constitutional illegitimacy of Article 12 of Law No. 91 of 2025 is deduced for violation of Articles 120, second paragraph, and 5 of the Constitution, because, due to the omission of obtaining the opinion of the State-Regions Conference, the principle of loyal cooperation was violated. The Region argues, in fact, that since the directive on air quality entered into force after the acquisition of the State-Regions Conference's opinion, no (additional and mandatory) opinion was obtained on the amendment providing for its transposition.

The question is ungrounded.

According to the constant case law of this Court (lately judgment No. 192 of 2024, which refers to judgments No. 139, No. 130, and No. 63 of 2024, No. 6 of 2023, No. 169 of 2020, and No. 237 of 2017), the principle of loyal cooperation does not govern the approval procedure of state laws. Judgment No. 63 of 2024 also specifies that this conclusion must be considered valid «even more so in domains attributable to an exclusive legislative competence of the State» (reference is made to judgments No. 6 of 2023, No. 137 of 2018, and No. 237 of 2017).

This Court has nevertheless affirmed that agreement (intesa) between the State and Regions «is imposed [...] as the cornerstone of loyal cooperation even when the implementation of provisions dictated by the state legislature is entrusted to delegated legislative decrees, adopted by the Government on the basis of Article 76 of the Constitution». This «in the event [...] of a strict intertwining between matters and competences» (judgment No. 169 of 2020, which refers to judgment No. 251 of 2016 and, in the same sense, judgment No. 72 of 2019).

Furthermore, it has been clarified that «when the delegation law is characterized by a degree of specificity and concreteness such as to entail an infringement of the Region's interest, since it has as its object the future regulation (by the delegated decree) of complex domains characterized by an intertwining of state and regional competences [...], the Region can and must assert it by challenging the delegation provision», clarifying that «[a] different solution would lead to a manifest, inadmissible circumvention of the peremptory sixty-day time limit established by Article 127, second paragraph, of the Constitution» (judgment No. 261 of 2017, which refers to judgment No. 251 of 2016).

In summary: adequate cooperation mechanisms are also required in the legislative procedure when provisions dictated by the delegating legislature must be implemented by the Government, through specific delegated legislative decrees, in the hypothesis where the intertwining between different material domains characterizing the concerned legislation cannot be unraveled by resorting to the criterion of prevalence, applicable only when the belonging of the core essence of the legislation itself to one matter rather than another is evident (ex plurimis, judgments No. 72 of 2019, No. 198 and No. 137 of 2018, No. 261, No. 170, and No. 114 of 2017, No. 287 and No. 251 of 2016) from a qualitative or quantitative point of view (judgments No. 21 and No. 1 of 2016, and No. 140 of 2015).

With the ground examined here, however, what is censured is the failure to express the prescribed opinion on an article of the delegation law providing for the transposition of the directive on air quality, complaining of a procedural flaw imputable to the violation of an ordinary law provision (namely Article 5, paragraph 1, letter b, of Legislative Decree No. 281 of 1997), and not a constitutional norm.

In judgment No. 237 of 2017, although concerning the different relationship between reinforced law and ordinary law, it is clarified that: «[w]hile it is true that the illegitimacy of a delegation law was recently declared for failing to provide for an agreement (intesa) with the Unified Conference (or with the State-Regions Conference, as the case may be) with a view to adopting delegated legislative decrees (judgment No. 251 of 2016), it must be emphasized that such pronouncement refers specifically to the relationship existing between the delegation law and the legislative decree, and that it would be incorrect to extend its scope to the different relationship existing between reinforced law and ordinary law. Such extension is indeed precluded by the circumstance, decisive in itself, that the legislative procedure is governed by a system of norms contained in the Constitution and parliamentary regulations to which the former refers for supplementary discipline (Articles 64 and 72 of the Constitution), with the consequence that a law, however reinforced, must be deemed precluded from regulating the legislative procedure of another law, even if of a different rank, with the (non-constitutional) law remaining in any case devoid of competence over such object».

Well then: the principles affirmed by judgment No. 237 of 2017 with reference to the relationship between reinforced law and ordinary law apply, a fortiori, also to the relationship between Legislative Decree No. 281 of 1997 and the delegation law object of review here. The complained flaw, therefore, does not exist.

For completeness, it is pointed out that, recently, this Court ruled on the theme of mechanisms for involving territorial autonomies in the legislative procedure regarding the coordination of public finance (judgments No. 152 of 2025 and No. 195 of 2024).

More specifically, in judgment No. 195 of 2024 it is observed that «the case law of this Court has essentially sought to affirm the need, on the part of the State which is the "custodian of extended public finance" (ex plurimis, judgment No. 103 of 2017) also in relation to the correct application of EU-unit constraints for which it is responsible, to acquire adequate evidentiary elements on the sustainability of the amount of the contribution by the entities from whom it is requested», clarifying, however, that this was functional «to preventing the adoption of "blind cuts", which besides potentially proving unsustainable for territorial autonomies, with unpredictable repercussions on services offered to the population, would not even allow a transparent weighting at the parliamentary level» and requiring, therefore, in relation to this specific requirement and from the perspective of the new European economic governance, which also provides for the temporal lengthening of net expenditure containment measures mentioned in the Structural Budget Plan, «substantial, and not merely formal, compliance with the principle of loyal cooperation».

The factual scenario of the current review is different and it cannot be deemed that the requirement of loyal cooperation, as a modification of the ordinary legislative procedure, mandates the expression of an opinion also on all individual amendments presented during the relative path, merely due to the fact that regional competences are involved. In the present case, the State-Regions Conference had already expressed its general opinion and the further opinion on the amendment subsequently approved was not imposed by the need for rationality of budgetary choices, a financial invariance clause having been provided for which the delegated legislative decrees must take into account in implementing the delegation, when concretely establishing which new tasks – given said clause – may be effectively conferred upon the regions.

9.– By the second ground of the Region of Lombardy's appeal (coinciding with the third ground of the appeals of the Regions of Piedmont and Veneto), the constitutional illegitimacy of Article 12, paragraph 2, of Law No. 91 of 2025 is deduced for violation of the principle of loyal cooperation under Articles 5 and 120, second paragraph, of the Constitution, in that the provision mandates that the legislative decrees referred to in paragraph 1 be adopted only upon receiving the opinion of the Unified Conference referred to in Article 8 of Legislative Decree No. 281 of 1997, rather than upon prior agreement (intesa) (which, moreover, in the view of the Regions of Piedmont and Veneto, should have intervened within the State-Regions Conference).

The question is ungrounded.

As already highlighted by this Court (judgments No. 72 of 2019 and No. 251 of 2016), when it comes to implementing provisions dictated by the state legislature, the application of the principle of loyal cooperation, in forms allowing adequate regional involvement, is inescapable only when an inextricable intertwining of exclusive (state), concurrent, and residual matters exists, none of which is prevalent, neither from a qualitative nor from a quantitative point of view.

In the present case, instead, the matter «environmental protection» is prevalent, falling within the exclusive legislative power of the State pursuant to Article 117, second paragraph, letter s), of the Constitution.

Said prevalence is evidenced by the following data: i) Directive 2024/2881/EU on air quality falls within European competence in environmental matters, by virtue of Article 192, paragraph 1, TFEU, cited as the legal basis by the directive itself; ii) the object of the directive is ambient air quality and the Recitals recall «risks of an environmental nature»; iii) in the challenged provision, references to air quality prevail – and this is the quantitative profile; iv) the purpose of the challenged provision – and this is the qualitative profile – is environmental remediation, relative to which other material domains of regional legislative competence are in a secondary position.

Since environmental protection constitutes the prevalent matter, the opinion of the Unified Conference referred to in Article 8 of Legislative Decree No. 281 of 1997 ensures an adequate and sufficient regional involvement by itself.

10.– By the fourth ground of the Region of Lombardy's appeal, the constitutional illegitimacy of Article 12 of Law No. 91 of 2025 is deduced also for violation of Article 3 of the Constitution, as regards reasonableness, Article 97 of the Constitution, as regards sound administration, and Article 118 of the Constitution, as regards adequacy.

The provision would establish inter-institutional synergies and a subsidiary state intervention, activable only in case of insufficiency of regional measures, without indicating timelines, participatory modalities, and adequate coordination mechanisms, thereby failing to guarantee sufficient protection of regional interests, in conflict with Article 97 of the Constitution (which should be construed as imposing the establishment of structures and organizational modules aimed at ensuring optimal functionality of administrative action).

The appellant argues that Article 12 of Law No. 91 of 2025 appears to reiterate the model in force since Legislative Decree No. 155 of 2010, despite such model having already been deemed insufficient by the European Union.

The question is ungrounded.

10.1.– According to the consolidated orientation of this Court, in matters referred to in Article 117, second paragraph, of the Constitution, choices concerning the allocation of administrative functions are also reserved to the state legislature (judgments No. 151 of 2024 and No. 189 of 2021), choices that are subject to review only in the case of their manifest unreasonableness. Such manifest unreasonableness does not occur here.

Article 12 of Law No. 91 of 2025 dictates criteria and principles of delegation giving particular emphasis to initiatives aimed at ensuring «synergy», «integration», and «coordination», this being precisely the content of the (first) delegation criterion referred to in letter a).

Paragraph 1, letter a), of the same Article 12, moreover, by setting forth principles and guiding criteria, establishes that: i) synergy must be ensured between actions relating to the remediation of ambient air quality and actions relating to sectors affecting major emission sources; ii) necessary integration and coordination measures must be provided between planning and programming acts regarding air quality and those regarding transport, mobility, energy, industry, energy efficiency, and agriculture; iii) institutional venues and procedures must be provided for the impulse and coordination of shared action, at the territorial and national levels, between authorities competent for air quality and authorities competent for such sectors.

Therefore, there can be no doubt that, as the delegated legislature must define «institutional venues and procedures for the impulse and coordination of shared action, at the territorial and national levels», the delegated decrees must assign a significant role to state authorities as well. The delegation criteria do not relegate the initiative of the latter solely to an eventual and ex post phase, but contemplate involvement of the State ex ante as well, primarily through impulse and coordination measures.

Paragraph 1, letter b), again of Article 12, further assigns a central role to "synergy" among the actions of the various institutional actors involved, providing for intense state involvement. Indeed: i) synergy must be ensured between air quality remediation measures adopted ordinarily by regional and local authorities and complementarily by state authorities; ii) the competence of the State to adopt national measures is established whenever regional plans cannot allow the achievement of air quality values in areas influenced, in a determining manner, by emission sources over which regions have no administrative and legislative competence or, even in the absence of such condition, whenever the contents of the measures are defined in agreements signed by interested regional authorities and all state authorities competent over the relevant emission sectors.

The State, therefore, maintains a central role and the distribution of tasks is by no means manifestly unreasonable. In light of this finding, the very reference to the peculiarities of the "Po Valley", insistently found in all regional challenges, is incapable of leading to a different conclusion.

10.2.– As to, moreover, the censure profile concerning the absence of indications of timelines, participatory modalities, and adequate coordination mechanisms, such organizational instruments will have to be better identified in the implementing legislative decrees, a delegation law not being required to directly provide detailed regulation.

In the case under examination, administrative functions, taking their nature into account, were attributed to the most appropriate territorial level.

Indeed, these are administrative activities that cannot ordinarily be allocated other than to regional and local authorities, also because account must be taken of the specificities of each territory and the circumstance that such activities must integrate with regional and local planning instruments, such as urban planning, energy plans, transport plans, and development plans. Therefore, such competences cannot be placed primarily and "directly" upon the State, as the appellant Region would wish.

The assessment allocating administrative functions to the regions in the present case, while simultaneously providing various forms of ex ante and ex post coordination with the State, is respectful of Article 118 of the Constitution and, therefore, of the principles of subsidiarity, differentiation, and adequacy. Consequently, the prerequisites for finding a violation of Articles 3, 97, and 118 of the Constitution in the terms framed in the appeal are not met.

11.– The Regions of Piedmont and Veneto, by the first ground of their appeals, deduced the constitutional illegitimacy also of Article 12, paragraph 1, letter b), of Law No. 91 of 2025, for violation of Article 117, second paragraph, letter s), of the Constitution, with reference to the matter «environmental and ecosystem protection», as well as Article 118, first paragraph, of the Constitution and the principles of subsidiarity, differentiation, and adequacy contemplated therein, for the correct allocation of administrative functions among the territorial entities of the Republic.

According to the appellants, Article 12, paragraph 1, letter b), of Law No. 91 of 2025 would be constitutionally illegitimate because it mandates the ordinary attribution of air remediation measures to regional and local authorities, limiting – instead – state intervention.

The challenged provision would ignore the proven inadequacy of regional and local levels – especially in the Po Valley – to guarantee European standards, and this would conflict with the exclusive legislative competence of the State in environmental protection (Article 117, second paragraph, letter s, of the Constitution) and with the principle of adequacy (Article 118, first paragraph, of the Constitution), which require such functions to be attributed to the State when regional and local levels prove structurally unsuitable. It would indeed be illegitimate to reproduce the model for distributing competences in air quality matters previously introduced by Legislative Decree No. 155 of 2010, which proved inadequate.

The censure cannot be upheld.

Regarding the parameter of Article 117, second paragraph, letter s), of the Constitution, invoked indeed in conjunction with other constitutional parameters, it suffices to observe that precisely by virtue of it the State adopted Article 12 of Law No. 91 of 2025, thereby exercising its exclusive legislative competence. Therefore, no violation of such parameter can be deemed integrated with reference to the legislative activity carried out by the State, nor can it be maintained that the latter, being the holder of exclusive legislative competence, should necessarily have "entrusted" itself with related administrative competences as well, while departing from the constitutional principle of subsidiarity. Moreover, following the reform of Title V of the Constitution, the so-called "principle of parallelism of functions" was overcome, so that administrative functions may also be attributed to an entity different from the holder of the relative legislative competence, on the basis of criteria identified by Article 118, first paragraph, of the Constitution, according to which «[a]dministrative functions are attributed to Municipalities unless, to ensure their unitary exercise, they are conferred upon Provinces, Metropolitan Cities, Regions, and the State, on the basis of principles of subsidiarity, differentiation, and adequacy».

As to the parameter of Article 118, first paragraph, of the Constitution, it suffices to refer to what was already stated in point 10 above.

12.– By the second ground of their appeals, the Regions of Piedmont and Veneto deduced the constitutional illegitimacy of Article 12, paragraph 1, letter b), of Law No. 91 of 2025 «for the same reasons and on the same terms indicated in the preceding censure» (first ground of appeal) also for violation of Articles 3, 97, and 117, first paragraph, of the Constitution, with the concomitant indirect infringement of regional legislative and administrative competences under Articles 117, third and fourth paragraphs, and 118 of the Constitution.

Following the declaration of partial inadmissibility of this censure reasoned in point 7.7.2 above, only the profile of violation of Articles 3 and 97 of the Constitution remains, with concomitant indirect infringement of regional legislative and administrative competences under Articles 117, third and fourth paragraphs, and 118 of the Constitution.

In this part, the censure proves ungrounded, for the same reasons already set forth in point 10 above, with reference to the fourth ground of the Region of Lombardy's appeal, to which reference should therefore be made. Nor is the reference to the «indirect infringement of legislative and administrative competences recognized by the Constitution to Regions» (under Articles 117, third and fourth paragraphs, and 118 of the Constitution) relevant. Such grievance, indeed, on the one hand, is proposed simply for the purpose of demonstrating the "redundancy" of the complained flaws; on the other hand, moreover in truly extreme summary, it evokes a simple "derived" constitutional illegitimacy, which is not supported by arguments additional to those spent with reference to the parameters that the appellants themselves define as "substantive".

per these reasons

THE CONSTITUTIONAL COURT

joines the proceedings,

1) declares inadmissible the questions of constitutional legitimacy of Article 12, paragraph 3, of Law No. 91 of June 13, 2025 (Delegation to the Government for the transposition of European directives and the implementation of other European Union acts - European Delegation Law 2024), raised, with reference to Articles 3, 81, 97, 118, and 119 of the Constitution, by the Region of Lombardy, and with reference to Articles 3, 81, third paragraph, 97, 117, first paragraph, and 119, fourth paragraph, of the Constitution, by the Regions of Piedmont and Veneto, by the appeals indicated in the heading;

2) declares inadmissible the questions of constitutional legitimacy of Article 12 of Law No. 91 of 2025, raised, with reference to Article 117, third and fourth paragraphs, of the Constitution, by the Region of Lombardy, by the appeal indicated in the heading;

3) declares inadmissible the questions of constitutional legitimacy of Article 12 of Law No. 91 of 2025, raised, with reference to Article 117, first paragraph, of the Constitution, in relation to Directive (EU) 2024/2881 of the European Parliament and of the Council of October 23, 2024, on ambient air quality and cleaner air for Europe, by the Regions of Piedmont and Veneto, by the appeals indicated in the heading;

4) declares ungrounded the questions of constitutional legitimacy of Article 12 of Law No. 91 of 2025, raised, with reference to Articles 5, 120, second paragraph, 3, 97, and 118 of the Constitution, by the Region of Lombardy, by the appeal indicated in the heading;

5) declares ungrounded the questions of constitutional legitimacy of Article 12, paragraph 2, of Law No. 91 of 2025, raised, with reference to Articles 5 and 120, second paragraph, of the Constitution, by the Regions of Lombardy, Piedmont, and Veneto, by the appeals indicated in the heading;

6) declares ungrounded the questions of constitutional legitimacy of Article 12, paragraph 1, letter b), of Law No. 91 of 2025, raised, with reference to Articles 3, 97, 117, second paragraph, letter s), third and fourth paragraphs, and 118 of the Constitution, by the Regions of Piedmont and Veneto, by the appeals indicated in the heading.

Decided in Rome, at the seat of the Constitutional Court, Palazzo della Consulta, on May 6, 2026.

Signed:

Giovanni AMOROSO, President

Massimo LUCIANI, Rapporteur

Roberto MILANA, Director of the Registry

Filed in the Registry on July 23, 2026