JUDGMENT NO. 57

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, Antonella SCIARRONE ALIBRANDI, Massimo LUCIANI, Maria Alessandra SANDULLI, Roberto Nicola CASSINELLI, Francesco Saverio MARINI,
has delivered the following

JUDGMENT

in the proceedings regarding the constitutionality of Articles 34(2) and 50 of Piedmont Regional Law no. 9 of 8 July 2025 (Annual Law for the Reorganization of the Regional Legal System. Year 2025), initiated by the President of the Council of Ministers with an appeal served on 8 September 2025, filed with the registry on the following day, registered under no. 37 of the 2025 register of appeals, and published in the Official Gazette of the Republic, no. 41, First Special Series, of the year 2025.

Having considered the entry of appearance by the Piedmont Region;

Having heard Judge Marco D’Alberti as reporting judge at the public hearing of 10 March 2026;

Having heard State Attorney Maria Luisa Spina for the President of the Council of Ministers and Attorney Giulietta Magliona for the Piedmont Region;

Having deliberated in the council chamber on 10 March 2026.

Statement of Facts

1.– By an appeal served on 8 September 2025, filed with the registry on 9 September 2025 (reg. appeal no. 37 of 2025), the President of the Council of Ministers, represented and defended by the State Attorney General’s Office, challenged Articles 34(2) and 50 of Piedmont Regional Law no. 9 of 8 July 2025 (Annual Law for the Reorganization of the Regional Legal System. Year 2025).

The first challenged provision, titled "Application of ecological flow,” establishes that "[i]n watercourses of a torrential nature, canals or portions thereof not classified as rivers by the Region, and in watercourses or stretches thereof classified as rivers characterized by recurrent seasonal water deficits, taking into account the non-constant regulation of water flow, the ecological flow shall be calculated dynamically based on the flow rate present in the abstraction section and may not exceed 30 percent of said actual flow rate.”

In the appellant's view, the challenged provision would allow for an increase in water abstraction from an individual watercourse and would therefore infringe upon the State’s exclusive legislative competence regarding the protection of the environment and the ecosystem, as provided for in Article 117(2)(s) of the Constitution, in relation to Article 76(1, 2, 3, 4, and 7), Article 95(4 and 6), Article 121(4), Article 144(1), and Part B of Annex 4 to Part III of Legislative Decree no. 152 of 3 April 2006 (Environmental Regulations), as well as Article 12-bis of Royal Decree no. 1775 of 11 December 1933 (Approval of the Consolidated Text of the Laws on Waters and Electrical Installations).

The same provision is also claimed to conflict with Article 117(1) of the Constitution, in relation to the principle of non-deterioration of watercourses, set forth in Article 4 of Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000, establishing a framework for Community action in the field of water policy.

1.1.– Article 50 of the same Piedmont Regional Law no. 9 of 2025 is also challenged.

In amending Annex A of Piedmont Regional Law no. 19 of 29 June 2009 (Consolidated Text on the Protection of Natural Areas and Biodiversity), the challenged provision, in paragraph 1, establishes the following: "[n]o. 26 of Annex A (Cartography of regional protected natural areas, contiguous areas, and natural safeguard zones) of Regional Law 19/2009 is replaced by the following: ‘26) Monte Fenera Natural Park - Scale 1:25,000’ (Annex 1).”

Paragraph 2 further provides that "[n]o. 90 of Annex A of Regional Law 19/2009 is replaced by the following: ‘90) Protected natural areas and contiguous area of the Po river belt - West Turin - Scale 1:25,000: - Contiguous area of the Piedmont Po river belt’ (Annex 2).”

In the appellant's view, the challenged regional provision, by providing for a new perimetration of two regional protected areas, would entail a reduction in landscape protection and a violation of the principle of landscape co-planning. Consequently, said provision is claimed to conflict with Articles 9 and 117(2)(s) of the Constitution, in relation to Articles 134(1)(c), 135(1), 142(1)(f), and 143(2) of Legislative Decree no. 42 of 22 January 2004 (Code of Cultural Heritage and Landscape, pursuant to Article 10 of Law no. 137 of 6 July 2002), Articles 3 and 18 of the implementing rules of the Regional Landscape Plan, approved by Regional Council Resolution no. 233-35836 of 3 October 2017, as well as Article 22 of Law no. 394 of 6 December 1991 (Framework Law on Protected Areas).

2.– Firstly, the appellant claims the unconstitutionality of Article 34(2) of Piedmont Regional Law no. 9 of 2025.

The challenged provision allegedly introduced a new method for calculating ecological flow – to be understood as the minimum flow of watercourses – which would entail its reduction and thus allow for an increase in abstractions.

This assessment allegedly falls outside regional competence, as the appropriate setting for regulating minimum vital flow and ecological flow is the planning phase, as established by Articles 76(4) and 121(4) of Legislative Decree no. 152 of 2006 regarding the water protection plan, and by Article 95 of the same decree regarding the water balance plan (reference is made to the judgments of this Court no. 153 of 2019 and no. 229 of 2017).

The provisions regarding water protection – under Articles 76(4), 95, 121(4), and 144 of Legislative Decree no. 152 of 2006, and Article 12-bis of Royal Decree no. 1775 of 1933 – fall under the subject matter of environmental protection, attributed to the State’s exclusive legislative competence under Article 117(2)(s) of the Constitution, which encompasses both the guarantee of ecological flow levels and measures safeguarding the balance of the water budget.

2.1.– Regional competencies regarding water protection could be legitimately exercised only if they pursue higher standards compared to those provided by State legislation.

Conversely, the limitation of ecological flow established by the challenged provision would introduce lower quality objectives than those set by State legislation and broad-area sectoral measures (reference is made to this Court's judgment no. 28 of 2013).

2.2.– Furthermore, the challenged provision is claimed to conflict with Article 117(1) of the Constitution, in relation to Article 4 of Directive 2000/60/EC, which sets out the principle of non-deterioration of water bodies.

3.– Secondly, the appellant claims the unconstitutionality of Article 50 of the same Piedmont Regional Law no. 9 of 2025, for violation of Articles 9 and 117(2)(s) of the Constitution, in relation to Articles 134(1)(c), 135(1), 142(1)(f), and 143(2) of the Cultural Heritage Code, as well as Articles 3 and 18 of the implementing rules of the Regional Landscape Plan (PPR) and Article 22 of Law no. 394 of 1991.

3.1.– Article 50 of Piedmont Regional Law no. 9 of 2025 amends Annex A of Regional Law no. 19 of 2009, replacing the cartographies relating to the Monte Fenera Natural Park protected area and the contiguous area of the Po river belt, respectively.

This would entail a reduction in the perimeters of the indicated natural areas. These are assets which, as they are subject to special environmental protection, should also be considered "of landscape interest” pursuant to Articles 134(1)(c) and 142(1)(f) of the Cultural Heritage Code.

Therefore, given the adoption of the PPR, the involvement of the Ministry of Culture would be necessary for the revision of park plans and the perimeters of protected natural areas, pursuant to Articles 135(1) and 143(2) of the Cultural Heritage Code.

Such a regulatory framework would be fully consistent with the incremental logic of landscape assets inherent in Legislative Decree no. 42 of 2004, which does not provide for regulations for the revision or elimination of said assets (reference is made to this Court's judgment no. 164 of 2021).

In the appellant's view, the obligation of co-planning with the Ministry, already provided for by Article 143(2) of the Cultural Heritage Code, particularly in the event of a de-perimetration, arises from the provisions of the PPR and Articles 3 and 18 of its implementing rules.

In conflict with said obligation, the changes to the boundaries of regional natural parks, introduced by the challenged provision, would introduce a unilateral reduction of areas subject to landscape protection.

The appellant emphasizes that, although State legislation distinguishes between the activity of classifying and establishing parks and natural reserves of regional and local interest and the activity of preparing regional landscape plans (reference is made to this Court's judgment no. 276 of 2020), in the case at hand, the PPR refers, regarding perimetration, to the provisions of Piedmont Regional Law no. 19 of 2009, as amended by the challenged provision.

In the view of the State defense, Article 50(1 and 2) would therefore conflict with Articles 134(1)(c), 135(1), 142(1)(f), and 143(2) of the Cultural Heritage Code, thus violating Articles 9 and 117(2)(s) of the Constitution.

3.2.– Approaching the public hearing, on 17 February 2026, the State Attorney General’s Office filed a defense brief in which it reiterated the admissibility and merits of the constitutionality questions raised in the appeal.

4.– By an act filed on 29 September 2025, the Piedmont Region entered an appearance, requesting that the constitutionality questions proposed by the President of the Council of Ministers be declared inadmissible or, in any event, unfounded.

4.1.– With reference to the challenges regarding Article 34(2) of Piedmont Regional Law no. 9 of 2025, the regional defense preliminarily provided a broad illustration of the relevant regulatory framework.

The Piedmont Region refers, in particular, to: 1) the Decree of the Ministry of the Environment and Protection of Land and Sea – Directorate General for the Safeguarding of Territory and Waters of 13 February 2017, no. 30 (Guidelines for updating methods to determine minimum vital flow in order to ensure the maintenance of ecological flow in watercourses to support the achievement of environmental objectives defined pursuant to Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000) (hereinafter: the Guidelines); 2) the Resolution of the Po River District Basin Authority – Permanent Institutional Conference of 14 December 2017, no. 4 (Directive for the determination of ecological flows to support the maintenance/achievement of environmental objectives set by the Hydrographic District Management Plan and subsequent reviews and updates) – the so-called ecological flow directive (hereinafter also: DDE); 3) the Water Protection Plan, approved by Resolution of the Piedmont Regional Council of 2 November 2021, no. 179-18293; 4) the Regulation of the President of the Piedmont Regional Executive of 27 December 2021, no. 14 (Provisions for the implementation of ecological flow); 5) the Resolution of the Piedmont Regional Executive of 27 March 2023, no. 14, no. 36-6674, titled "Implementation of the Regional Water Protection Plan (PTA) referred to in D.C.R. no. 179-18293 of 2 November 2021 and D.P.G.R. of 27 December 2021 no. 14/R. Approval of general guidelines for the experimentation of ecological flow release and the dynamic management of water scarcity scenarios,” with which the general guidelines for the experimentation of ecological flow release, as well as for the management of critical situations in relation to possible minor temporary releases, were defined.

4.1.1.– Given this, the regional defense considers the constitutionality question regarding Article 34(2) of Piedmont Regional Law no. 9 of 2025 to be inadmissible.

Faced with a complex and layered regulatory framework, the appeal is considered entirely generic, as it leaves the terms of the alleged conflict between the challenged regional provision and State discipline indeterminate. In particular, the reasons for the violation of the DDE, which defines the rules and parameters that must be used by the regions to determine ecological flow, are not indicated.

In essence, the appellant failed to indicate which State norm prevents the Region from varying the criteria for defining minimum flow established by the Water Protection Plan and Regional Regulation no. 14 of 2021 (in this regard, reference is made to this Court's judgment no. 113 of 2024).

4.1.2.– Furthermore, the constitutionality question regarding Article 34(2) of Piedmont Regional Law no. 9 of 2025 would also be inadmissible due to a lack of harm.

The regional defense highlights that, based on Article 34(1) of the same Piedmont Regional Law no. 9 of 2025, the application of ecological flow is deferred to 31 December 2026. This would impact the entry into force of the new discipline introduced by the challenged provision. Furthermore, the Piedmont Region must establish the criteria based on which to apply the new methods for calculating ecological flow. Being devoid of actual application at this stage, the challenged provision would not produce any legal constraint for the time being.

4.2.– Regarding the constitutionality questions of Article 50 of Piedmont Regional Law no. 9 of 2025, the Piedmont Region considers them inadmissible, due to a lack of adequate justification regarding the reasons for the conflict of the challenged provision with each of the multiple constitutional and interposed parameters invoked.

4.2.1.– The questions would, in any case, be unfounded in light of the principles affirmed by constitutional jurisprudence, in particular in judgment no. 115 of 2023, which addressed the issue of the re-perimetration of regional parks, concluding that it is up to the regions to define the boundaries of a regional natural park area.

The regional defense disputes the appellant's assumption that regional competence, once exercised (and recognized in the PPR), could only be expressed through the expansion of protected areas and not in the opposite direction, requiring the prior consent of ministerial bodies in such cases. Beyond conflicting with the principle of revocability of landscape protection constraints, such an assumption could discourage regional choices to strengthen protection, inducing the regional legislature not to make them for fear of never being able to revoke them, even when a renewed weighing of interests might demand it.

4.2.2.– In the view of the Piedmont Region, the alleged subjection of the activity of revising the boundaries of protected areas to the necessity of co-planning, provided for by Articles 135(1) and 143(2) of the Cultural Heritage Code, would end up subverting the distribution of competencies under Article 117(2)(s) of the Constitution, as it could transform the landscape constraint from a "derived” legal qualification arising from the existence of the environmental constraint into a legal prerequisite for the definition of competencies under Article 117 of the Constitution (reference is made to this Court's judgment no. 44 of 2001).

The regional defense believes, in fact, that the assessment of the necessity of environmental protection for an area belongs solely to the regions. The landscape constraint would intervene only subsequently and as a consequence of the necessity of environmental protection. Should the reasons for environmental protection that led to the identification and perimetration of an area cease to exist, the constraint itself would no longer have reason to exist *ex se*. Indeed, with respect to the environmental protection underlying the identification of protected areas, the landscape constraint has a derived and consequential nature.

4.2.3.– The regional defense deduces that, in the appellant's framework, the reference to regional parks and reserves and their related external protection territories, contained in Article 142(1)(f) of the Cultural Heritage Code, would entail an "attraction” of regional legislative competence for defining the boundaries of protected areas into the exclusive State competence regarding landscape protection.

Therefore, under this aspect as well, the constitutionality question would be unfounded.

4.2.4.– Furthermore, in the view of the Piedmont Region, the constitutionality question regarding Article 50 of Piedmont Regional Law no. 9 of 2025, promoted in reference to Article 134(1)(c) of the Cultural Heritage Code, would be unfounded due to the irrelevance of the interposed parameter with respect to the content of the grievance (reference is made to this Court's judgments no. 69 of 2024 and no. 161 of 2021).

Article 134(1) of Legislative Decree no. 42 of 2004 identifies three categories of constrained landscape assets, distinguished based on the type of constraint: by administrative provision (letter a); by law (letter b); and by landscape plan (letter c). When drafting its own PPR, the Piedmont Region did not resort to this third method of imposing the constraint, limiting itself to the recognition of the assets referred to in the other two categories of Article 134(1). Therefore, the reference to letter c) of Article 134(1) would be entirely irrelevant and superfluous.

4.2.5.– The Piedmont Region also deduces the inadmissibility and, in any case, the lack of merit of the question promoted in reference to Article 3 of the PPR implementing rules, dedicated to the "Role of the PPR and [its] relations with territorial plans and programs.”

The inadmissibility of the question would derive both from the irrelevance of the invoked parameter and from the generic nature of the challenges.

Pursuant to the cited Article 3, the obligation of co-planning would concern (only) the verification of compliance with the PPR of the area plans of the parks included in the list contained in Article 3(7), a verification that must be carried out jointly between the Ministry and the Region.

Moreover, this provision would not affect the challenged provision, which contains no reference to the activity or content of park plans. Furthermore, such plans regulate regional protected areas insofar as they possess the requirements to be classified as parks and, consequently, as landscape-protected areas. In the event that the landscape constraint ceases due to the loss of the park qualification, no planning would be envisaged and, therefore, the reference to Article 3 of the PPR implementing rules would not be relevant. Furthermore, area plans are intended to regulate permitted and prohibited uses and activities, without intervening in the definition of boundaries, which was done by the regional legislature pursuant to Piedmont Regional Law no. 19 of 2009.

4.2.6.– Regarding Article 18 of the PPR implementing rules (dedicated to "Protected natural areas and other biodiversity conservation areas”), the regional defense observes that this provision expresses the obligation for regional and State planners to attribute the qualification of landscape asset (with the consequent necessity of submitting works affecting such assets to the landscape authorization procedure) to the protected areas resulting from the current regional legislation, according to a dynamic reference to Piedmont Regional Law no. 19 of 2009 and its subsequent updates.

This would be a necessary provision, considering the "recognitory” rather than "constitutive” nature of the constraints operated by the PPR, as well as the necessity to adapt the same constraints to the actual status of the assets considered.

4.2.7.– Likewise inadmissible or, in any case, unfounded would be the constitutionality question regarding the violation of Article 22 of Law no. 394 of 1991.

This interposed parameter would constitute the very State regulatory reference – then declined at the regional level by Piedmont Regional Law no. 19 of 2009 – used by the regional legislature to perform the partial revision of the boundaries of protected areas, referred to in the challenged Article 50 of Piedmont Regional Law no. 9 of 2025.

After highlighting the minor nature of the changes made by the challenged provision to the indicated natural areas, the regional defense observes that over the years, changes, even in reduction, to the perimetrations of regional protected areas have already taken place without prior agreement with the Ministry of Culture.

5.– Pursuant to Article 6 of the Supplementary Norms for Proceedings before the Constitutional Court, the Italian Association of Hydroelectric Producers – Assoidroelettrica, acting as *amicus curiae*, filed a written opinion, admitted by presidential decree on 2 February 2026, requesting the rejection of the constitutionality questions concerning Article 34(2) of Piedmont Regional Law no. 9 of 2025.

5.1.– The *amicus curiae* observes, first of all, that the obligation to respect an ecological flow set in a fixed and static measure would be disproportionate with respect to small streams and rivers most exposed to flow fluctuation phenomena, due to the alternation of low and flood states. Such watercourses would be characterized by particularly resilient flora and fauna, capable of resisting even in conditions of extreme water scarcity. Faced with such characteristics of intrinsic flow instability, the sacrifice imposed on hydroelectric producers – deriving from the need to respect a fixed and static ecological flow regime – would be incongruous and disproportionate.

5.2.– Given this, Assoidroelettrica believes that the challenged provision constitutes a virtuous solution from an environmental perspective. The introduction of a flexible and dynamic criterion would, in fact, allow for adjusting the actual value of the flow necessary for achieving the objectives set by Article 4 of Directive 2000/60/EC, without prejudicing the public interest in pursuing the energy transition, enshrined in Article 16-*septies* of Directive (EU) 2023/2413 of the European Parliament and of the Council of 18 October 2023, amending Directive (EU) 2018/2001, Regulation (EU) 2018/1999, and Directive no. 98/70/EC regarding the promotion of energy from renewable sources and repealing Council Directive (EU) 2015/652; as well as in Article 3 of Legislative Decree no. 190 of 25 November 2024, titled "Discipline of administrative regimes for the production of energy from renewable sources, in implementation of Article 26(4 and 5)(b and d) of Law no. 118 of 5 August 2022.”

Considerations in Law

6.– With the appeal indicated in the epigraph, the President of the Council of Ministers challenged, firstly, Article 34(2) of Piedmont Regional Law no. 9 of 2025.

This provision establishes that "[i]n watercourses of a torrential nature, canals or portions thereof not classified as rivers by the Region, and in watercourses or stretches thereof characterized by recurrent seasonal water deficits, taking into account the non-constant regulation of water flow, the ecological flow shall be calculated dynamically based on the flow rate present in the abstraction section and may not exceed 30 percent of said actual flow rate.”

In the appellant's view, the introduction of these new methods for calculating ecological flow would allow for an increase in abstractions from the individual watercourse and, therefore, would infringe upon the State’s exclusive legislative competence regarding the protection of the environment and the ecosystem, under Article 117(2)(s) of the Constitution, in relation to Articles 76(1, 2, 3, 4, and 7); 95(4 and 6); 121(4); 144(1), and Part B of Annex 4 to Part III of Legislative Decree no. 152 of 2006, as well as Article 12-bis of Royal Decree no. 1775 of 1933.

The same provision is also claimed to conflict with Article 117(1) of the Constitution, in relation to the principle of non-deterioration of watercourses, referred to in Article 4 of Directive 2000/60/EC.

7.– Preliminarily, the Piedmont Region excepted the inadmissibility of the questions as the appeal is claimed to be generic, leaving the terms of the conflict between State discipline and the challenged regional provision indeterminate.

7.1.– The exception is unfounded.

The appeal is supported by arguments sufficient and suitable for understanding the essence of the grievances. The President of the Council of Ministers complains that, with the challenged provision, the Piedmontese legislature reduced the water flow suitable for ensuring ecological flow and, consequently, allowed for an increase in abstractions from the individual watercourse, thus violating both the exclusive State legislative competence on the subject of environmental and ecosystem protection, under Article 117(2)(s) of the Constitution, and the principle of non-deterioration of watercourses, under Article 4 of Directive 2000/60/EC. It can therefore be considered that the appellant identified the reasons for the proposed conflict and reached "the minimum threshold of clarity and completeness necessary to allow examination of the merits of the question promoted” (among the most recent, judgments no. 65 and no. 32 of 2025; in the same sense, judgments no. 133, no. 95 and no. 94 of 2024).

Moreover, the motivation of the appeal did not prevent the regional defense from elaborating a complete and exhaustive argumentative defense on the merits with reference to all the parameters and aspects invoked by the appellant (in this sense, among many, judgments no. 4 of 2026, no. 80 of 2025 and no. 53 of 2020).

8.– Also preliminarily, the Piedmont Region excepted the lack of motivation of the constitutionality questions under examination due to the failure to indicate the reasons why the challenged provision would conflict with what was established by the Basin Authority in the 2017 ecological flow directive. Furthermore, the appeal would not indicate which State norm prevents the Region from varying the criteria for defining minimum vital flow fixed in the Regional Water Protection Plan and in Regional Regulation no. 14 of 2021.

8.1.– This exception is also unfounded.

As seen, the President of the Council of Ministers denounces the violation of the State legislative competence regarding environmental protection and complains of the conflict between regional legislative discipline and that set by the State legislature in the exercise of such competence, punctually referred to by the same appellant. Conversely, the lack of motivation excepted by the Piedmont Region relates to the conflict of the challenged regional provision with discipline not having legislative rank, which is unsuitable for integrating the parameter of the constitutionality judgment.

9.– Finally, the Piedmont Region excepted the inadmissibility of the questions due to a lack of harm from the challenged provision.

The regional defense highlights, firstly, that Article 34(1) of Piedmont Regional Law no. 9 of 2025, which was not challenged, deferred the application of ecological flow to 31 December 2026 throughout the regional territory, without prejudice to ongoing experiments. This postponement should also be referred to the new ecological flow discipline introduced by the challenged paragraph 2 of the same Article 34.

Secondly, the regional defense observed that, to give concrete implementation to the challenged provision, the Piedmont Region will have to indicate the new methods for calculating ecological flow, as well as the criteria based on which to apply the new discipline. Being devoid of actual application at this stage, the challenged provision would currently not produce any legal constraint.

9.1.– This exception is also unfounded.

It must first be noted that, regardless of any consideration on the reported lack of application of the challenged Article 34(2), it entered into force on 25 July 2025 and since then has neither been repealed nor modified in any way. According to the constant jurisprudence of this Court, proceedings promoted *via principalis* presuppose the mere publication of a regional law deemed harmful to the distribution of competencies, regardless of the effects it has produced (among many, judgments no. 122 of 2025, no. 195 of 2017, no. 262 of 2016 and no. 118 of 2015). In fact, the interest to propose and pursue the appeal must be identified "in the protection of the legislative competencies as distributed in the Constitution: the correct framing of legislative competencies represents, in this sense, the utility expected from the requested ruling” (among many, judgments no. 122 of 2025 and no. 101 of 2021; in the same sense, judgments no. 56 of 2020, no. 178 of 2018 and no. 195 of 2017).

Therefore, the lack of concrete application of the challenged regional provision is irrelevant for the purposes of the admissibility of the questions under examination.

10.– On the merits, the constitutionality question raised in reference to Article 117(2)(s) of the Constitution is well-founded.

10.1.– Preliminarily, it must be noted that State legislation regarding water protection has undergone significant evolution over time.

While the 1933 Consolidated Text focused on regulating water resources aimed mainly at satisfying the needs of electrical energy production, Legislative Decree no. 152 of 2006 attributed primary importance to the protection of water for its environmental profile. Said decree transposed Directive 2000/60/EC, which, in Article 1(1)(a), established the principle of non-deterioration of water, in harmony with Article 191 of the Treaty on the Functioning of the European Union and Article 37 of the Charter of Fundamental Rights of the European Union, which demand a high level of environmental protection.

10.2.– The most relevant norms for the case at hand are contained in Articles 95, 96(3), 144, and 145 of Legislative Decree no. 152 of 2006.

In particular, Article 95 imposes measures to ensure the balance of the water budget and establishes that water abstraction concessions must provide for releases aimed at ensuring minimum vital flow in water bodies, as reiterated by the subsequent Article 96.

The flow is defined according to the criteria adopted by the Minister of the Environment and Energy Security with a specific decree, following agreement with the State-Regions Conference. With the aforementioned Ministerial Decree no. 13 of 2017, the Minister of the Environment adopted the Guidelines for updating methods for determining minimum vital flow, a concept substantially coinciding with that of ecological flow, as clarified by the Guidelines themselves.

The latter provide, among other things, for the establishment, at the Institute for Environmental Protection and Research (ISPRA), of the National Catalog of ecological flow calculation methods, the definition of which is handled by a National Technical Table chaired by the Minister of the Environment and Energy Security. ISPRA, the National Research Council – Water Research Institute (CNR-IRSA), the National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), the Higher Institute of Health (ISS), as well as District Basin Authorities and the Regions (Article 2(2) of Ministerial Decree no. 30 of 2017) participate in this body. Thus, the preeminent role of the sectoral Minister and highly specialized technical-scientific institutes in the determination of ecological flow emerges, and the name itself confirms the environmental importance of such a water body regime.

Article 144 of the Environmental Code, in paragraph 3, implements the principle of non-deterioration of Article 4 of Directive 2000/60/EC, establishing that "the regulation of water uses is aimed at their rationalization, for the purpose of avoiding waste and favoring the renewal of resources, of not prejudicing the water heritage, the livability of the environment, agriculture, fish farming, aquatic fauna and flora, geomorphological processes, and hydrological balances.”

In parallel, Article 145 of the same Legislative Decree no. 152 of 2006 provides that it is up to the Basin Authority to define the water balance and plan water economics and that abstraction concessions must ensure the level of flow necessary not to damage ecosystems. The Basin Authority has within it, as a policy-making body, the permanent institutional conference, in which the Presidents of the regions included in the hydrographic district, the Minister of the Environment and Energy Security, the Minister of Infrastructure and Transport, the Head of the Civil Protection Department, the Minister of Agriculture, Food Sovereignty and Forestry, and the Minister of Culture participate. The Authority draws up the basin plan, in compliance with which the regions prepare water protection plans, which they then transmit to the Minister of the Environment and the Basin Authorities for competency checks.

The primary importance of State bodies and planning activity in the definition of the water budget emerges.

10.3.– The constant jurisprudence of this Court has traced the provisions on water protection ‒ contained mainly in Part III of Legislative Decree no. 152 of 2006, titled "Regulations on soil defense and the fight against desertification, the protection of water from pollution, and the management of water resources” and, in particular, in its Section II titled "Protection of water from pollution” ‒ to the subject of "environmental protection,” falling under the State’s exclusive legislative power under Article 117(2)(s) of the Constitution (judgment no. 117 of 2020).

The provisions of Legislative Decree no. 152 of 2006, invoked by the appellant as interposed parameters, respond indeed to "purposes of prevention and reduction of pollution, remediation of polluted water bodies, improvement of the state of waters, pursuit of sustainable and lasting uses of water resources, maintenance of the natural self-purification capacity of water bodies and the capacity to support large and diversified animal and plant communities, mitigation of the effects of floods and droughts, protection and improvement of the state of aquatic ecosystems, terrestrial ecosystems, and wetlands directly dependent on aquatic ecosystems in terms of water needs” (judgments no. 229 of 2017 and no. 254 of 2009; similarly, judgment no. 246 of 2009).

These are aims that directly relate to the protection of the intrinsic conditions of water bodies and aim to guarantee certain qualitative and quantitative levels of water (judgments no. 117 of 2020, no. 153, no. 65 and no. 44 of 2019, no. 68 of 2018 and no. 229 of 2017).

10.4.– With specific reference to the discipline of minimum vital flow, this Court affirmed that "[t]he guarantee of the minimum vital flow of the water body, as it is aimed at avoiding the exhaustion of the source, must be considered to concern the ‘conservation’ of the water asset and not merely its use, with the consequence that the relevant discipline must be considered attracted into the exclusive competence of the State, pursuant to Article 117(2)(s) of the Constitution, regarding environmental protection” (judgment no. 28 of 2013). Although referring to a case of competing regional and State competencies on the subject of mineral and thermal waters, the principles affirmed by this ruling appear extendable to the discipline of water resources.

10.5.– In light of the highlighted regulatory and jurisprudential framework, Article 34(2) of the Piedmont Regional Law no. 9 of 2025 reveals itself to be in conflict with the aforementioned State discipline regarding water protection.

Without respecting the administrative competencies, conditions, and procedures provided for by said State discipline, the challenged regional provision provides for a drastic and unilateral modification of the criteria for applying ecological flow. It establishes that such a hydrological regime "may not exceed 30 percent of the actual flow rate.” Further reductions are therefore even permitted, which are reflected in the corresponding increase in abstractions that can be authorized.

This is a regulatory intervention which, besides not being preceded by an adequate investigation, nor supported by any technical-scientific parameter, paradoxically allows for increasing abstractions precisely in those situations which – due to being characterized by "recurrent seasonal water deficits” – entail a reduction in water flow.

The regional legislature's choice to establish a limit on the application of ecological flow deviates from the criteria established by State law for the purpose of conserving the good health status of watercourses and results in jeopardizing the pursuit of environmental protection objectives that ecological flow is aimed at guaranteeing.

10.6.– It must also be considered that, in light of constant constitutional jurisprudence, the environment delineates a "transversal” subject, in relation to which different competencies are manifested, which can well be regional, while State determinations of environmental protection responding to needs deserving of uniform discipline throughout the national territory remain the responsibility of the State (judgments no. 158 of 2021 and no. 407 of 2002).

The regional legislature, in the exercise of its competencies, is permitted to increase the levels of protection fixed by the State legislature. Regions, therefore, can adopt norms that interfere with environmental protection only if they raise the standard of protection provided by national legislation, which serves as a minimum threshold for safeguarding the environment, legitimizing regional regulatory interventions only in the sense of raising protection (among many, judgments no. 144 of 2022, no. 291 and no. 7 of 2019, no. 174 and no. 74 of 2017). In this sense, Article 76(7) of Legislative Decree no. 152 of 2006 provides that "[t]he regions may define higher environmental quality objectives, as well as identify further uses of water bodies and related quality objectives.”

In the case at hand, however, the unilateral reduction of the application of ecological flow modifies in a detrimental sense the environmental standard set by State discipline, since it impacts the balance of the water budget, allowing for the increase of abstractions from watercourses.

10.7.– In conclusion, Article 34(2) of Piedmont Regional Law no. 9 of 2025 results in conflict with essential profiles of State and European legislation, such as the principle of non-deterioration of water quality, the necessary compliance of regional plans with the basin plan, and the indispensable contribution of highly specialized technical-scientific entities for the determination of the correct ecological flow.

Failure to comply with ordinary State norms entails the violation of Article 117(2)(s) of the Constitution, which entrusts the discipline of environmental protection to the exclusive legislative power of the State. Article 117(1) is also violated, in relation to the principle of non-deterioration of water quality provided for by Directive 2000/60/EC.

10.8.– As an effect of the declaration of unconstitutionality of Article 34(2) of Piedmont Regional Law no. 9 of 2025, the previous paragraph 1, which defers the application of ecological flow until 31 December 2026, is entirely emptied of concrete prescriptive content.

11.– The President of the Council of Ministers also promoted constitutionality questions regarding Article 50 of Piedmont Regional Law no. 9 of 2025, in reference to Articles 9 and 117(2)(s) of the Constitution.

In amending Piedmont Regional Law no. 19 of 2009, the challenged provision replaces the cartography contained in Annex A of said law, in the part referring, respectively, to the Monte Fenera Natural Park and the contiguous area of the Piedmont Po river belt.

In the appellant's view, the new perimetration of regional natural parks, introduced by the challenged provision, would exclude some zones from the protected areas. This would entail a reduction in landscape protection and a violation of the principle of landscape co-planning. Therefore, the violation of Articles 9 and 117(2)(s) of the Constitution is denounced, in relation to Articles 134(1)(c), 135(1), 142(1)(f), and 143(2) of the Cultural Heritage Code; Articles 3 and 18 of the implementing rules of the Regional Landscape Plan, as well as Article 22 of Law no. 394 of 1991.

12.– Preliminarily, the regional defense excepted the inadmissibility of the constitutionality questions, due to a lack of adequate motivation regarding the conflict of the challenged regional provision with each of the cited parameters.

The exception is unfounded.

As is known, the requirement for adequate motivation underlying an appeal arises in strict terms in proceedings promoted *via principalis*, in which the appellant has the burden not only to identify the challenged provisions and the constitutional parameters of which it denounces the violation but also to substantiate the reasons for the deduced conflict with clear, complete, and sufficiently articulated arguments (among the most recent, judgments no. 198, no. 126 and no. 106 of 2025, no. 169 of 2024, no. 125 of 2023, no. 265, no. 259 and no. 135 of 2022, no. 170 of 2021 and no. 279 of 2020).

In the case at hand, the exception is unfounded due to the general nature of the grievance asserted in these proceedings. The President of the Council of Ministers, in fact, believes that, once a regional natural park is established and its relative boundaries are defined, the regional legislature can no longer operate any reductive intervention without the necessary involvement of State bodies, because otherwise landscape protection in those areas would be compromised.

It follows that, in the case at hand, the motivational burden can be considered satisfied – albeit succinctly – by the appellant, which correctly identified the constitutional parameters it assumes are violated (Articles 9 and 117(2)(s) of the Constitution) and punctually referred to the complex of State provisions regarding the protection of protected natural areas.

13.– On the merits, the question is well-founded.

13.1.– It must be stressed that the fundamental principles for the establishment and management of protected natural areas are dictated by Law no. 394 of 1991, introduced "for the purpose of guaranteeing and promoting, in a coordinated form, the conservation and enhancement of the country's natural heritage” (Article 1(1)).

The national framework law classifies protected natural areas into parks and natural reserves and, in relation to the local dimension of naturalistic interests, attributes to the Regions the competence for the establishment and classification of parks and natural reserves of regional and local interest (Article 2(8) and Article 22(3)).

Regarding the subsequent modification of the perimeter of the regional protected area, this Court recognized that it can be carried out both during the adoption or modification of the park plan and by regional law, provided it is done in compliance with the procedure regulated by Article 22 of Law no. 394 of 1991, including consultation with local authorities (judgments no. 235, no. 221 and no. 115 of 2022, no. 276 and no. 134 of 2020).

In implementation of said State discipline, Article 10-*bis* of Piedmont Regional Law no. 19 of 2009, introduced by Article 6(1) of Piedmont Regional Law no. 16 of 3 August 2011, titled "Amendments to Regional Law 29 June 2009, no. 19 (Consolidated Text on the Protection of Natural Areas and Biodiversity),” established that "[t]he partial modification of the boundaries of protected areas delimited in Annex A or in the relative founding laws, necessary for the purpose of guaranteeing the effective achievement of the aims referred to in this law, is carried out with a specific resolution of the Regional Executive, in agreement with the interested local authorities and after hearing the binding opinion of the competent council commission.”

13.2.– Regarding the case that comes to light in these proceedings, it must first be noted that, with the aforementioned Regional Council Resolution no. 233-35836 of 2017, the PPR was approved based on the agreement signed in Rome on 14 March 2017 between the Ministry for Cultural Heritage and Activities and the Piedmont Region.

Article 135(1), third period, of the Cultural Heritage Code, in fact, places the obligation to prepare regional landscape plans "jointly between the Ministry and the regions, limited to the landscape assets referred to in Article 143(1)(b, c, and d), in the forms provided for by the same Article 143.”

In this regard, this Court affirmed that State discipline aimed at protecting the environment and the landscape requires a broad-spectrum institutional strategy, which is expressed in planning activity extended throughout the national territory entrusted jointly to the State and the Regions (judgments no. 6 of 2023, no. 240 and no. 130 of 2020, no. 86 of 2019 and no. 66 of 2018). In this perspective, Article 135, by providing for the obligation of joint preparation of the landscape plan, places an unalterable principle of State legislation, which, in turn, is a reflection of the necessary unitary imprint of landscape planning and aims to guarantee, through the participation of ministerial bodies in proceedings on the subject, the effective and uniform protection of the environment (again judgments no. 6 of 2023 and no. 240 of 2020).

13.3.– With reference to landscape planning, Article 143(1)(c) of the Cultural Heritage Code establishes that "[t]he preparation of the landscape plan includes at least: [...] c) recognition of the areas referred to in paragraph 1 of Article 142, their delimitation and representation on a scale suitable for identification, as well as the determination of use prescriptions intended to ensure the conservation of the distinctive characters of said areas and, compatibly with them, their enhancement.”

Therefore, in the preparation of the landscape plan, the areas referred to in Article 142(1), i.e., those protected *ope legis*, including natural parks and regional reserves, contemplated by letter f) of the same paragraph 1 of Article 142, are the object of "recognition,” in the sense that they constitute a fact from which landscape planning cannot prescind (judgment no. 115 of 2023).

The landscape plan has, in fact, the function of an instrument for recognizing the territory subject to planning, not only for the purposes of safeguarding and enhancing landscape assets but also in the perspective of sustainable development and conscious use of land, so as to allow the identification of measures necessary for the correct insertion, in the landscape context, of land transformation interventions (judgment no. 172 of 2018).

In the logic of an integrated protection system, Article 140(2) of the Cultural Heritage Code prescribes the necessary transfusion into the landscape plan of the discipline contained in the individual constraint provisions. Only for this hypothesis, "and by reason of this integration between different moments of the same protection matter, so that the plan that follows can only take note of the pre-existing constraint provisions, the irrevocability of the discipline contained in the latter is justified” (judgments no. 115 of 2023 and no. 135 of 2022).

13.4.– In the presence of the PPR, the result of planning activity jointly carried out by the State and the Region, the intervention of the Piedmontese legislature, aimed at unilaterally modifying the discipline of two regional natural areas through the reduction of some protected areas, conflicts with the aforementioned prescriptions of the Cultural Heritage and Landscape Code, which, through the participation of ministerial bodies in proceedings on the subject, aim to guarantee the effective and uniform protection of the environment, entrusted to the exclusive legislative competence of the State.

Indeed, as an effect of the reductionist revision of the two regional protected areas, a part of the territories, previously included within the scope of the plan’s provisions, was unilaterally removed from landscape protection, imposed on the same areas by Article 142(1)(f) of the Cultural Heritage Code.

The remodulation in a restrictive sense of the constraint should have been evaluated within the landscape co-planning referred to in Articles 135 and 143(2) of the Cultural Heritage Code.

This Court affirmed that the region "operates on the procedural level by addition, and never by subtraction, in the sense that regional competence can be spent only for the purpose of enriching the catalog of landscape assets, by virtue of the knowledge that the authority closest to the territory where they arise has of them, and not to lighten it by force of considerations conflicting with those assumed by the State” (judgment no. 164 of 2021). In fact, "the levels of environmental protection set by the State legislature could be expanded and not derogated in a detrimental sense by the regional legislature, […] so that the lowering of the level of landscape protection would also violate Article 9 of the Constitution” (judgment no. 90 of 2023; in the same sense, judgments no. 115 of 2023 and no. 135 of 2022). The Region, therefore, could not unilaterally derogate in a detrimental sense from the environmental protection standards established in the co-decided PPR.

13.5.– In the opposite sense, the reference made by the regional defense to what was affirmed in judgment no. 115 of 2023, which addressed the issue of the re-perimetration of regional parks, concluding that it is up to the regions to define the boundaries of a regional natural park area, is of no avail.

In fact, the case examined by said ruling concerned a provision of the Liguria Region which – unlike the Piedmont Region – was devoid of a PPR. In the case at hand, instead, landscape assets and their relative protection regime have already merged into the PPR – the result of the joint preparation of the Region with the State – with which the recognition of such assets and the preparation of relative use prescriptions were carried out.

13.6.– Likewise irrelevant is the reference to the principle of revocability of regional environmental protection constraints relating to the perimetration of protected areas, on the assumption that the landscape constraint of the PPR has a "derived and consequential nature.”

It has long been recognized, in fact, that protection, both environmental and landscape, by burdening a complex and unitary asset, assumes a primary value and falls within the exclusive competence of the State. It "precedes and in any case constitutes a limit to the protection of other public interests assigned to the concurrent competence of the Regions in the matter of government of the territory and enhancement of cultural and environmental assets” (judgment no. 164 of 2021).

13.7.– The constitutionality of Article 50 of Piedmont Regional Law no. 9 of 2025 must therefore be declared in reference to Articles 9 and 117(2)(s) of the Constitution, the latter in relation to Articles 135(1), 142(1)(f), and 143(2) of the Cultural Heritage Code, with the absorption of the further questions promoted in the appeal.

FOR THESE REASONS

THE CONSTITUTIONAL COURT

1) Declares the unconstitutionality of Article 34(2) of Piedmont Regional Law no. 9 of 8 July 2025 (Annual Law for the Reorganization of the Regional Legal System. Year 2025);

2) Declares the unconstitutionality of Article 50 of Piedmont Regional Law no. 9 of 2025.

Thus decided in Rome, at the seat of the Constitutional Court, Palazzo della Consulta, on 10 March 2026.

Signed:

Giovanni AMOROSO, President

Marco D’ALBERTI, Reporting Judge

Roberto MILANA, Director of the Registry

Filed in the Registry on 27 April 2026