Hidden in plain sight: The green constitutional force of Article 11 TFEU

Abstract

The escalating climate crisis and major advances in climate litigation question the existence of constitutional protection for environmental rights in the EU legal system. For forty years, Article 11 TFEU has mandated the integration of environmental protection requirements into all EU policies. Yet it remains largely dormant in the case law even as the EU Green Deal evidenced progress in policymaking. Although the provision is often dismissed as unenforceable by the scholarship, this article argues that Article 11 TFEU provides for a constitutional obligation akin to a general principle of EU law with significant untapped potential. Through textual, systemic and teleological analysis, we establish Article 11's binding nature and constitutional significance. The article retraces the evolution of the CJEU's case law and demonstrates how, despite inconsistencies, Article 11 TFEU already performs all functions generally fulfilled by general principles of EU law, thanks notably to recent grand chamber judgments of the Court of Justice. Accordingly, we propose an interpretation of this principle that both respects judicial precedents and realizes its true legal potential, offering a robust constitutional foundation for advancing environmental protection within the Union's legal framework at a time when such protections are increasingly vital.

1. Introduction

Around the globe, environmental protection is becoming a constitutional matter. While courts increasingly enforce environmental rights, ¹ the Court of Justice of the European Union (CJEU) has been reluctant to uphold constitutional guarantees on environmental protection provided by the Treaties. Paradoxically, it is the Court of Justice that asserted in ADBHU environmental protection to be an ‘essential objective’ of the Communities, despite the silence of the Treaties over 40 years ago. ² The incorporation of environmental protection into the EU constitutional framework followed as a gradual enterprise.

Article 11 TFEU results from this progressive incorporation. As a standalone principle, it commands the integration of environmental protection requirements into the definition and implementation of EU policies and activities. It has long been criticized in the literature as a weak, ³ ‘vague’, ⁴ ‘programmatic’, ⁵ essentially unenforceable, provision. This state of affairs has pushed scholars to advocate for the recognition of a fundamental right on the basis of Article 37 CFR, a provision close in wording to Article 11 TFEU. ⁶

Nevertheless, Article 11 TFEU provides the strongest constitutional foundation for upholding environmental protection at Union level. The context is ripe for uncovering its constitutional significance and justiciability. Amidst a growing environmental crisis fuelled by unabated climate change and biodiversity loss, the European Green Deal policy agenda has materialized the integration principle with the goal to marshal ‘all EU actions and policies’ for the transition to sustainability. ⁷ With the political momentum now fading, it has never been more important to clarify the Union's constitutional obligations for environmental protection.

Essentially, this paper questions whether Article 11 TFEU is a general principle of Union law. Article 11 TFEU sets a clear constitutional obligation that concerns not only the Union but also its Member States within the scope of Union law. Although the CJEU has been inconsistent in upholding Article 11 TFEU and never explicitly recognized it as setting a general principle of Union law, its case law suggests that it is one in everything but name.

Although general principles of Union law have been derived from a variety of sources, ⁸ it is not uncommon for them to originate in the Treaties. ⁹ This is most famously the case with the principle of sincere cooperation, ¹⁰ as well as with the principle of subsidiarity. ¹¹ More recently, the principle of solidarity was ‘discovered’ by the CJEU notably on the basis of Article 2 TEU. ¹² While Article 11 TFEU is, and has long been intended to be, binding, the approach of the CJEU has hindered the respect of the principle of environmental integration. Yet, recent case law has opened new avenues for upholding environmental protection as part of EU constitutional law. ¹³ As such, Article 11 TFEU now performs all three functions generally performed by general principles: review the legality of EU legislation, support judicial interpretation and fill normative gaps in EU law. ¹⁴ In this context, the recognition of Article 11 TFEU as providing for a general principle of Union law would clarify the case law and ensure that ‘the law is observed’.

This article offers several contributions to the scholarship. By undertaking an in-depth analysis of Article 11 TFEU supported by a systematic review of the case law, it sheds new light on this provision. ¹⁵ In the process, we show that Article 11 TFEU differs from the horizontal clauses introduced by the Lisbon Treaty, which are largely deemed aspirational, and to which it has been assimilated. ¹⁶ The article clarifies the relationship between Article 11 TFEU and Article 37 CFR, which is the object of some confusion. ¹⁷ Finally, this article makes novel proposals to give this constitutional provision its effet utile.

Considering textual, systemic and teleological interpretations, we first demonstrate that Article 11 TFEU provides a legally binding and enforceable constitutional obligation for the Union and its Member States (section 2). We then analyze how the CJEU has approached the provision since its introduction in the Treaties; showing that in spite of its inconsistency the CJEU has given Article 11 TFEU the attributes of general principles of Union law (section 3). As the saying goes, if it looks like a duck, swims like a duck and quacks like a duck, then it probably is a duck. Assuming it is indeed a duck, the article proceeds to question why Article 11 TFEU should be recognized openly as a general principle and the implications of such a recognition (section 4).

2. The constitutional obligation: Interpreting Article 11 TFEU

When interpreting Union law, including to determine the existence of a general principle of Union law, ¹⁸ the Court of Justice resorts to different, non-mutually exclusive modes of interpretation: textual, holistic, historical and teleological interpretation. ¹⁹ This section shows that all different modes of interpreting Article 11 TFEU, textual (section 2.A), holistic (section 2.B), historical and teleological (section 2.C), point to the existence of a constitutional, legally binding and enforceable obligation.

A. The wording

According to Lenaerts and Gutiérrez-Fons, the CJEU ‘will never ignore the clear and precise wording of an EU law provision’. ²⁰ Similarly, the Grand Chamber of the Court of Justice recently emphasized that ‘an interpretation of a provision of EU law cannot have the result of depriving the clear and precise wording of that provision of all effectiveness.’ ²¹ Article 11 TFEU provides: ‘Environmental protection requirements must be integrated into the definition and implementation of the Union’s policies and activities, in particular with a view to promoting sustainable development.’ We contend that the wording of this provision is neither symbolic nor weak but clear and binding.

Firstly, Article 11 TFEU uses ‘must’ to express a legally binding and enforceable obligation. It does not ask its addressees ‘to deploy best efforts…or to consider…the integration of environmental requirements.’ ²² As Francis Jacobs once wrote, it ‘is not merely programmatic but imposes legal obligations.’ ²³ Unlike the commonly used ‘shall’, ‘must’ indeed expresses an active duty, as evidenced by other linguistic versions of the Treaties using terms that express the same binding nature under Article 11 TFEU. ²⁴

The common meaning of the words used in the provision further spells out what the obligation consists of. On the one hand, the provision refers to ‘environmental protection requirements’ (emphasis added). This formulation both strengthens the sense of the obligation entailed by Article 11 TFEU and fleshes it out. A close reading of the Treaties suggests that ‘requirements’ should not only be understood literally in the legal sense of the term, ²⁵ but also as ‘what is required’, in other words what is necessary to protect the environment. ²⁶ This formulation sets a general principle without specifying exactly what environmental protection requirements are mandated as these will depend on the policy and situation in question. As such, it leaves an appropriate amount of discretion to the Union and the Member States. The exercise of this discretion can be adequately reviewed by the CJEU in light of the provision's express reference to its purpose, which is to promote sustainable development, one of the Union's overarching objectives. ²⁷

Article 11 TFEU was expressly given a broad scope. It covers ‘the Union policies and activities’ without distinction or restriction. This general wording entails that the principle of environmental integration ought to span the Union's whole exercise of its competences. The term ‘activities’ refers to pre-Lisbon’s Article 3 EC, which listed the different spheres of activity of the Community, from the prohibition of custom duties among Member States to the strengthening of the competitiveness of industry . As such, the reference to both policies and activities introduced in Amsterdam conveys the comprehensive scope of the constitutional obligation. ²⁸

Moreover, Article 11 TFEU covers ‘the definition and implementation’ of Union policies and activities. From the moment that a Union policy or activity is pursued, the Union's institutions define policy choices that are then implemented not only by the Union itself—its institutions, bodies and agencies—but also by the Member States. All of them are the addressees of the principle of environmental integration. As such, the scope of the obligation encompasses the whole decision-making process, from the definition of the basic political choices to execution. It is also the opinion of Advocate General Kokott, who deduced from the combined reading of Article 11 TFEU and Article 37 CFR that, ‘compliance with EU environmental law is incumbent on all its institutions and bodies, irrespective of whether powers under environmental law are exercised.’ ²⁹ Moreover, it is commonly the responsibility of the Member States to implement Union law under the prevalent model of executive federalism and as per Article 291(1) TFEU. Therefore, it is also incumbent on them to ensure environmental protection within the scope of Union law. ³⁰

B. The system

The CJEU often considers the holistic interpretation of the Treaties. In this respect, a common objection to recognizing an Article 11 TFEU as a legally binding and enforceable constitutional provision is that it is merely one of several horizontal clauses, suggesting other provisions like Articles 9 and 12 TFEU should be treated the same way. ³¹ This does not withstand scrutiny.

Firstly, these provisions, laid down under Title II of the TFEU as ‘Provisions Having General Application’, were not all created equal. Article 7 TFEU requires consistency between policies and activities, and recalls the principle of conferral. Articles 8 to 13 TFEU are the broadly similar ‘horizontal clauses’. By contrast, Articles 14 to 16 TFEU are actual legal bases empowering the Parliament and Council to adopt legislation and providing for the legislative procedure. In addition, Articles 15 and 16 TFEU respectively lay down rights to access EU documents and data protection. Article 17 TFEU is the last of these Title II provisions and it regards the Union's (passive) respect for confessional and non-confessional organizations.

Secondly, among the more homogeneous ‘horizontal clauses’, Article 11 TFEU stands out. It is the strongest and most specific of such provisions. Unlike Article 11 TFEU, which explicitly resorts to ‘must’ to emphasize the mandatory nature of the constitutional obligation, all other horizontal clauses—including the principle of consistency provided by Article 7 TFEU—use the verb ‘shall’. While all linguistic versions of Article 11 TFEU use terminologies unambiguously expressing an active duty, it is not the case for other horizontal clauses, which rarely do so. ³²

The difference between Article 11 TFEU and other similar provisions is even starker when examining the nature of the obligation. Indeed, environmental protection requirements must be integrated into the definition and implementation of the Union's policies and activities. While some have spoken of ‘integration principles’ when referring to horizontal clauses, ³³ this characterization is inaccurate. Articles 8 and 10 TFEU on the elimination of inequalities and combating discriminations signify objectives with using such words as ‘aim’ and ‘promote’, while Articles 9, 12 and 13 TFEU are mere procedural obligations to consider a given issue by referring to ‘take into account’ or ‘pay full regard’. Even the principle of consistency of Article 7 TFEU merely provides ‘taking all objectives into account’. Hence, the integration principle is above the fray of other so-called ‘horizontal clauses’, and provides for a stronger and clearer constitutional obligation.

Also, Article 11 TFEU ought to be distinguished from another similar provision, Article 37 CFR. Both provisions largely repeat and reinforce each other, but the former is more specific, while benefitting from a broader scope of application than the latter. Article 11 TFEU refers to ‘environmental protection requirements’, while Article 37 TFEU can be read as more aspirational by referring to ‘a high level of environmental protection and the improvement of the quality of the environment’, which is the same formulation used by Article 3(3) TEU for the objectives of the Union. Furthermore, Article 11 TFEU has a broader scope, covering ‘the definition and implementation of the Union's policies and activities’ rather than just ‘policies’.

Critically, Article 11 TFEU is unconditioned, whereas Article 37 CFR needs implementation in secondary law to be justiciable. In accordance with Article 52(5) CFR, the prevalent interpretation of the Charter (confusingly) distinguishes between ‘rights’ and ‘principles’, which are different from general principles of Union law. Under the Charter, ‘principles’ must be implemented in secondary law to be justiciable and may only be used for the purposes of interpreting and reviewing the legality of implementing secondary law. ³⁴ Even though the distinction between Charter rights and principles is not clear-cut, it was confirmed by the Court of Justice since Association de médiation sociale. ³⁵ In this respect, Article 37 CFR is widely considered to belong to the category of principles under the Charter. ³⁶ Consequently, it lacks the legal force of a genuine fundamental right. ³⁷ These important restrictions do not apply to Article 11 TFEU.

C. The intent and purpose

It is not just textual and holistic interpretations that advocate for the recognition of Article 11 TFEU as a constitutional, legally binding and enforceable provision. It is also the spirit that animates this provision that can be traced back to the history of its introduction and gradual revisions in the Treaties. ³⁸

The principle of environmental integration underlying Article 11 TFEU is nearly as old as the emergence of environmental concerns in Europe. Environmental protection was not mentioned in the Treaties of Rome, nor was it originally contemplated as a policy of the European Economic Community. In the 1972 Paris Declaration, Member States’ Heads of State and Government proclaimed that, to achieve the economic objectives set out in Article 2 TEEC, the Community must lead an effective campaign to combat pollution and nuisances and protect the environment. ³⁹ The Declaration emphasized the contribution of an environmental policy to the sustainable attainment of the internal market objective. The Paris Declaration follows the UN Stockholm Declaration proclaiming that achieving environmental goals ‘will demand the acceptance of responsibility by citizens and community and by enterprises and institutions at every level, all sharing equitably in common efforts.’ ⁴⁰ Hence

it highlighted the transversal policy integration of environmental considerations which is central to the integration principle far beyond the simplistic idea of a strictly confined, yet omnipotent, environmental policy. ⁴¹ As Dhondt showed, the Stockholm Declaration inspired the principle of integration. ⁴² Similarly, the first environmental action plan of the Community refers to the need to integrate ecological factors in devising and implementing common policies. ⁴³

Even as environmental policy progressively integrated Community law and policy through the internal market backdoor, ⁴⁴ the constitutional breakthrough came from the Court of Justice's ruling in ADBHU. ⁴⁵ The Court's bold step was shortly thereafter confirmed by the pouvoir constituant in the Single European Act. While introducing environmental policy in the scope of supranational competences, that Treaty ‘gave birth to the integration principle’ under Article 130r(2) TEEC, ⁴⁶ by requiring that: ‘Environmental protection requirements shall be a component of the Community's other policies.’ This provision, which followed the specification of the different principles grounding environmental policy, represents the first iteration of the principle of integration that is today enshrined in Article 11 TFEU.

The principle of integration was progressively strengthened and erected as a standalone constitutional obligation of general application. The Maastricht Treaty both introduced environmental protection among the objectives of the Community and toughened the formulation of the integration principle, by providing that ‘environmental protection requirements must be integrated into the definition and implementation of other Community policies.’ ⁴⁷ The amendment specified the importance and wide scope of the obligation. ⁴⁸ The submission of the European Commission for the Intergovernmental Conference of 1991 evidences the reasoning behind the change. It underlined the necessity of improving environmental protection ‘in order to ensure sustainable growth’, and explained that the proposed amendments to the TEEC aimed at a ‘more effective action by the Union to protect the environment’, and sought ‘to facilitate and encourage consideration of environmental imperatives in the other policies’. ⁴⁹ For the Commission, the wording ‘shall be’ was imprecise and aspirational without imposing real obligations, and ought to be amended. ⁵⁰ A tighter and more forceful wording was advocated for, so that ‘genuine account be taken of the environment in the definition and implementation of other policies’. ⁵¹ The substitution of ‘shall be a component’ by ‘must be integrated’ sought to achieve this clarification.

Still, Member States did not satisfy themselves with the new, stronger formulation decided in Maastricht. In 1997, the Amsterdam Treaty further reinforced the Treaties’ environmental provisions, and moved the integration principle to Article 6 TEC. ⁵² The new provision read, ‘environmental protection requirements must be integrated into the definition and implementation of the Community policies and activities referred to in Article 3, in particular with a view to promoting sustainable development.’ ⁵³ The Member States believed that the integration principle was neglected despite growing environmental degradation because of its position under the environmental policy title. ⁵⁴ As a result, the integration principle was moved up to the Treaty's section on ‘Principles’, and its scope of application was extended not just to ‘Community policies’, but also to ‘activities’. The new position in the Treaties gave rise to original arguments that it sets a general principle of Community law. ⁵⁵ The new formulation and the positioning of the article further demonstrated the extension of the obligation to the entire body of Union law. ⁵⁶ The Lisbon Treaty confirmed this new position, so that Article 11 TFEU refers to ‘the Union's policies and activities’ without limitation. At the same time, Lisbon gave the Charter the same status than the Treaties. With Article 37 CFR restating in most part Article 11 TFEU, it emphasized the importance of environmental integration.

Finally, the reference to ‘promoting sustainable development’, which was added in Amsterdam, sought to ‘strengthen the link between environmental protection and other activities such as economic activities’. ⁵⁷ By connecting the constitutional obligation to the objectives of the Union, the reference promotes the holistic interpretation of the Treaties, ⁵⁸ and elucidates the understanding that sustainable development requires ‘a process of bringing environmental requirements closer to EU policies and activities’. ⁵⁹ Sustainable development is an overarching objective of the Union under Article 3(3) TEU, as the internal market ‘shall work for the sustainable development of Europe based on balanced economic growth and price stability, a highly competitive social market economy, aiming at full employment and social progress, and a high level of protection and improvement of the quality of the environment.’ The latter notion of ‘high level of protection’ echoes Article 191(1) TFEU, the basis of EU environmental policy, and Article 114 TFEU. Article 114(3) demands that the Commission ‘take as a base a high level of protection’ when making proposals to harmonize national laws for the establishment and functioning of the internal market concerning health, safety, consumer protection and environmental protection. ⁶⁰

While being the umbrella for the Union's economic, social and environmental objectives, the concept of sustainable development was defined and popularized by the Brundtland Report a decade before Amsterdam, as the ‘development that meets the needs of present generations without compromising the needs of future generations’. ⁶¹ The Commission concurred shortly after the Treaty of Nice when it announced in 2002 that: ‘Sustainable long-term economic development is compatible with environmental sustainability. To ensure this, environmental sustainability needs to be taken systematically into account in formulating economic and social policies.’ ⁶² Therefore, sustainable development balances social and economic priorities with environmental protection (and not the other way around), consistently with Article 11 TFEU. ⁶³

In conclusion, literal, holistic, historical and teleological interpretations of Article 11 TFEU all point to the existence of a clear and legally binding constitutional obligation.

3. Demise and renaissance of the environmental integration principle

The Court of Justice seized on the principle of environmental integration after its introduction in the Treaties. But, despite the progressive strengthening of what is now Article 11 TFEU by the Masters of the Treaties, the CJEU has been inconsistent over the past two decades in its approach to Article 11 TFEU (section 3.A). Yet, two recent grand chamber judgments may signal a break in the case law that could bolster the constitutionalization of environmental protection (section 3.B).

A. Judicial tergiversations

Even as the Court of Justice’s ADBHU ruling initiated the constitutionalization of environmental integration, ⁶⁴ the Court has been reluctant to uphold Article 11 TFEU over the past two decades. To analyze the case law, we searched for, read and coded the judgments of the CJEU as well as Advocate General Opinions mentioning Article 11 TFEU and any of its previous iterations (which we refer to as the principle of integration or principle of environmental integration for simplicity), as well as any related keywords up until the end of 2025. ⁶⁵ We also made additional searches concerning Article 37 CFR as this provision and Article 11 TFEU are similar in wording, despite differences in scope and purpose.

After the Single European Act was ratified, the Court of Justice was quick to act on the newly introduced principle of integration. The first ruling invoking then-Article 130r(2) dates to 1990 and concerns a matter of appropriate legal bases. ⁶⁶ The Court considered the principle of integration to determine the centre of gravity of an act for identifying that act's legal basis. ⁶⁷ If an act incorporates measures furthering environmental protection, it does not entail that it must be adopted on the basis of the Union's environmental competence provided that it has been taken on a more appropriate legal basis. ⁶⁸ In a broader fashion, the Court recently asserted regarding the choice of legal basis that, ‘the European Union must comply with [Article 11 TFEU] when it exercises one of its competences.’ ⁶⁹ The principle was used in multiple cases in support of the Court of Justice's reasoning to find acts valid or invalid due to their choice of legal basis. ⁷⁰ This case law justified the incorporation of environmental provisions in an array of policies, from the common commercial policy to agriculture and fisheries. ⁷¹ As such, the principle of integration has been used as a shield to protect legislation integrating environmental protection requirements.

The principle of integration played other roles in the 1990s and early 2000s. It supported justifications for measures otherwise incompatible with fundamental freedoms, as in the famous PreussenElektra. ⁷² In another case, the Court invoked the principle as ‘a provision which emphasizes the fundamental nature of [the environmental protection] objective and its extension across the range of those policies and activities’, to assert that traffic restrictions hindering free movement of goods in Austria's Inn Valley could be justified – even though the measure in question in this case, a total ban on heavy lorries, was found to be disproportionate. ⁷³ In addition, in Concordia Bus Finland, the Court of Justice extraordinarily opened the door for the use of environmental criteria for determining the economically most advantageous offer in public procurement. ⁷⁴ The acme of the case law was, in National Farmers’ Union, the Court's conclusion that the precautionary principle extended beyond the scope of environmental policy, thanks to the principle of integration. ⁷⁵ Since then, it is now widely admitted that the precautionary principle is a general principle of Union law. ⁷⁶ Yet, after National Farmers’ Union, the CJEU did not elevate Article 11 TFEU or any of the principles guiding environmental policy listed under Article 191(2) TFEU as general principles of Union law. The precautionary principle is an exception in the case law.

The Court of Justice stopped referring to the principle of integration as ‘a principle’ after National Farmers’ Union, even though it used this qualification throughout the 1990s. ⁷⁷ Since then, the Court either avoided qualifying the nature of the obligation, ⁷⁸ or assimilated the principle to the objective of environmental protection, ⁷⁹ even after successive Treaty revisions sought to strengthen the principle of integration and assert its character of a constitutional provision distinguished from the Union's objectives. Furthermore, the judicial approach to the principle of integration has since the 2000s been inconsistent, with the side-effect of weakening the very wording of Article 11 TFEU. ⁸⁰ The reasons for this inconsistency are unclear.

The case law on state aid illustrates the Court of Justice's tergiversations. In British Aggregates, the Court of Justice rebuffed the General Court's pretention that environmental protection requirements could justify selective advantages resulting from state aids, ⁸¹ while admitting that ‘account may in any event usefully be taken of the environmental objectives when the compatibility of the State aid measure with the common market is being assessed.’ ⁸² A dozen years later, the Hinkley Point C case yielded some mixed results. On the one hand, the Court of Justice affirmed that the Commission cannot declare an aid compatible with the internal market where it benefits an activity that would ‘contravene rules of EU law on the environment’, particularly given ‘the requirement to preserve and improve the environment, expressed in both the Charter and the FEU Treaty’. ⁸³ On the other hand, the Court rejected the idea that, beyond formal compliance with existing rules, negative effects of an aid on the environment should be taken into account. ⁸⁴ And it even seemed to restrict the scope of Article 11 TFEU in energy policy in the particular context of nuclear energy. ⁸⁵

Moreover, the Court of Justice repeatedly watered down the wording and meaning of the principle of environmental integration. In Brenner, a case of indirect discrimination, the Court asserted that, ‘no account can be taken on considerations relating to environmental protection otherwise than in the strict framework laid down by Directive 1999/62’. ⁸⁶ The Court of Justice's misreading is also clear from British Aggregates where the Court paid lip service to ADBHU and Article 11 TFEU while only discussing ‘the need to take account of’ environmental protection requirements. ⁸⁷ In other words, it satisfied itself that authorities had considered environmental protection, without asserting that it is an obligation or seeking to assess the appropriateness of their measures in view of environmental protection. ⁸⁸ A fortiori, the Court abandoned the idea that environmental protection requirements must be integrated in Horvath, where it ruled that: ‘The Community legislature may…decide to promote environmental protection.’ ⁸⁹ Despite its initial adherence to the principle of integration, the Court progressively moderated, if not outrightly ignored, the wording and significance of the principle of integration even while it was strengthened in the Treaties. The change of tone is striking from the early years of the Court's case law, such as in Chernobyl, where the Court had professed that the principle of integration ‘reflects the principle whereby all Community measures must satisfy the requirements of environmental protection’. ⁹⁰

By retaining a restrictive interpretation of Article 11 TFEU, the Court defied calls from Advocates Generals and the General Court alike. The Court of Justice's past neglect of Article 11 TFEU is clear from the examination of Advocate General Opinions. Since 2000, Advocate Generals have generally referred to the principle of integration twice as often as the CJEU, ⁹¹ evidencing the latter's reluctance. ⁹² Multiple Advocate Generals have called on the Court of Justice to overcome its ambiguous and fragmented approach by expressly recognizing that environmental protection can justify measures frustrating the Union's fundamental freedoms, even where those are discriminatory in nature. ⁹³ For some, the principle of integration should likewise justify restrictions to fundamental rights, such as the right to property and the general principle of business secrecy in the name of environmental protection. ⁹⁴ In a notable Opinion, Advocate General Cosmas even considered that the principle of integration ‘appears to impose on the Community institutions a specific and clear obligation which could be deemed to produce direct effect in the Community legal order.’ ⁹⁵ In general, Advocates General did not shy away from asserting that environmental protection requirements, because of their ‘transverse and fundamental nature’, can take precedence over other Union's fundamental objectives. ⁹⁶ The General Court has recently followed suit in a series of rulings related to chemicals by considering that environmental protection as required by Article 11 TFEU prevails ‘over economic considerations’, even where the adverse economic consequences ‘are substantial’. ⁹⁷

The introduction of Article 37 CFR, given the same value than the Treaties since Lisbon, does not explain the inconsistency of the Court of Justice. While some scholars have enthusiastically welcomed the few (autonomous) references made by the Court to Article 37, they also underlined the significant prudence of the Court in engaging with this provision. ⁹⁸ Furthermore, in all instances where Article 37 was upheld by the Court in absence of a reference to Article 11 TFEU, the claim was directly related to the environmental policy competence of the Union. ⁹⁹ Otherwise, Article 37 CFR was discussed in combination with Article 11 TFEU. ¹⁰⁰ As such, Article 37 CFR is not an instrument of constitutional integration of environmental protection, unlike Article 11 TFEU, even if it can support ambitious interpretations of EU environmental law.

B. The judicial recognition of a general principle

While the Masters of the Treaties have repeatedly emphasized the constitutional and mandatory nature as well as the general scope of application of Article 11 TFEU, the CJEU has blown hot and cold on the question, undermining the importance of environmental protection in the EU constitutional order. Paradoxically, it is the same institution that has over the years admitted that Article 11 TFEU could fulfill all the functions generally performed by general principles of Union law.

General principles don’t fall from heaven, as Groussot once wrote. ¹⁰¹ There are two commonly accepted methods for the identification of general principles of Union law: judicial ‘discovery’ by the Court of Justice, in accordance with its mission to interpret the law and ensure that it is observed under Article 19(1) TEU; ¹⁰² and affirmation by the Treaties. ¹⁰³ It is commonly admitted that general principles of Union law perform at least three functions. ¹⁰⁴ Firstly, general principles fill normative gaps in Union law, notably ‘to ensure the autonomy and coherence of the EU legal system’. ¹⁰⁵ Secondly, they are used by the CJEU to interpret Union law and national law falling within the scope of Union law. ¹⁰⁶ Thirdly, they may be invoked as grounds of legal review. ¹⁰⁷ These three functions help distinguish general principles of Union law. Remarkably given the judicial inconsistency, Article 11 TFEU has, in the case law of the Court of Justice, already fulfilled all three functions, and more.

Firstly, the principle of environmental integration, since the very beginning, has been invoked by the Court of Justice to fill normative gaps in Union law. Article 11 TFEU and its previous iterations have been used in multiple cases, including, in recent decades, in support of the EU legislature's choice of a legal basis falling outside the environmental policy of the Union. As the Court puts it in the Titanium Dioxide case, the ‘principle implies that a Community measure cannot be covered by [Article 191 TFEU] merely because it also pursues objectives of environmental protection’. ¹⁰⁸ This case law justified the incorporation of environmental provisions in an array of policies, from the common commercial policy to agriculture, and transports. For instance, in Établissements Mondiet, the Court admitted the introduction of a measure prohibiting certain fishing techniques and equipment for environmental reasons in an act taken under the Common Fisheries Policy, rather than annul the act for an improper legal basis. ¹⁰⁹ The Court's use of the principle of integration to fill gaps in the law was not restricted to issues of choice of legal basis. The Court of Justice opened in Concordia Bus Finland the door for the use of environmental criteria for selecting offers in public procurement. ¹¹⁰ It did so in spite of the silence of the directive on public procurement, which only referred to ‘the most economically advantageous’ offer without explicitly considering any non-economic criteria. The Court of Justice found there that the directive ‘does not exclude the possibility for the contracting authority of using criteria relating to the preservation of the environment when assessing the economically most advantageous tender.’ ¹¹¹ The Court confirmed this finding two years later in an infringement ruling. ¹¹² By doing so, the Court clearly showed how Article 11 TFEU fills normative gaps to support environmental protection.

Secondly, Article 11 TFEU also served as an aid to interpret Union law. This is notably clear in State aid cases, where the Court admitted since British Aggregates that the assessment of the compatibility with the internal market of a State aid measure pursuing an environmental objective should be interpreted in view of the principle of environmental integration. ¹¹³ Fast forward to 2024, and a grand chamber judgment of the Court of Justice created a new precedent by interpreting corporate law in the light of Article 11 TFEU. In LivaNova, the concept of liability under the Sixth Company Law Directive has been interpreted ‘to prevent the undertaking which instigates the polluting activity from escaping its obligations towards its stakeholders as a result of the division of a public limited company under its control’. ¹¹⁴ Consequently, the Court invoked Article 11 TFEU to support an interpretation that extends liability as covering ‘not only defined liabilities, but also undefined liabilities, such as the costs of clean-up and environmental damage’. ¹¹⁵ This shows that, largely outside the remit of environmental law and policy, Article 11 TFEU can be instrumental to integrate environmental protection requirements in Union law through interpretation. ¹¹⁶

Thirdly, the Court of Justice recently accepted Article 11 TFEU as a ground for legal review. This was first done in 2021, with the Netherlands claiming that an EU ban on pulse fishing infringed Article 11 TFEU. The Court, in its judgment, confusingly sidestepped this issue, notably by considering that the claimant had not proven a manifest error of assessment on the part of the legislature. ¹¹⁷ Three years later, a grand chamber judgment of the Court in the Mobility Package case goes much further by reviewing the legality of two regulations and a directive on road transport and posted workers on the basis of Article 11 TFEU. ¹¹⁸ The Court does so by reading Article 11 TFEU in light of Article 37 CFR. It starts the analysis by noting that, ‘Article 11 TFEU is, by its nature, horizontally applicable, which entails that the EU legislature must incorporate environmental protection requirements into the European Union's policies and activities.’ ¹¹⁹ The Court of Justice walked a tightrope in its reasoning by claiming ‘necessary to take account of other measures undertaken by the EU legislature to limit the negative effects of road transport on the environment and to attain the overall objective of reducing polluting emissions, in order to determine whether there must be a finding that Article 11 TFEU, read in conjunction with Article 37 CFR, has been infringed.’ ¹²⁰ Still, the Court examines in details the environmental effects of the challenged provisions. ¹²¹ Even though the Court rejects the claims brought on the basis of Article 11 TFEU, it does so after concluding that the contested measures would not cause ‘significant negative effects’ on the environment. ¹²² As such, the Court sets an important benchmark for future legality reviews.

It is unclear at this stage whether the Mobility Package case, and to a lesser degree LivaNova, represents a sustainable break in the case law after two decades of a more muted approach. Both are grand chamber cases recently rendered by the Court of Justice, which underline the constitutional importance of the judgments. ¹²³ In LivaNova, the reference to Article 11 TFEU came in support of the Court's reasoning rather than to justify it. Nonetheless, it is the only provision mentioned by the Court outside of the Sixth Company Law Directive, which makes no mention of, or even indirect reference to, the environment in the recitals or the operative part. ¹²⁴ LivaNova thus reaffirms previous case law that Article 11 TFEU represents an aid to interpretation. For Mobility Package, which is more groundbreaking, the discussion of the Court was much more extensive as multiple provisions of the legislative package were challenged by Member States for breaching Article 11 TFEU, leading to an in-depth examination of the different arguments brought on this ground. Even though the Court found no violation by the Council and Parliament given the lack of clear negative effects on the environment, it developed remarkable benchmarks for the legality review. Interestingly, the judgment differs from the Advocate General's Opinion in the case, which also examined in detail the arguments of the parties based on Article 11 TFEU. Yet, unlike the Court, Advocate General Pitruzella rejected the idea that a legislation causing negative effects on the environment would breach Article 11 TFEU. ¹²⁵ Furthermore, the Advocate General's Opinion downplayed the importance and meaning of Article 11 TFEU and concluded that the EU legislature has a wide margin of discretion in striking a balance between various objectives and principles. ¹²⁶

Both of these grand chamber cases confirm that the principle of environmental integration as provided by Article 11 TFEU fulfills the three functions usually performed by general principles of Union law. Besides, the Court of Justice has long admitted in its case law that the principle of environmental integration could perform other, complementary functions. It considered the principle of integration to justify measures that could have otherwise been found to infringe the Union's fundamental freedoms. ¹²⁷ The Court's most radical move was arguably to seize the moment amidst the outbreak of the bovine spongiform encephalopathy (or ‘mad cow disease’) in order to elevate the precautionary principle as a general principle of Union law by relying on the integration principle. ¹²⁸

From gap-filling to aid for interpretation and ground for legal review, the Court of Justice has relied on the principle of integration to fulfill functions normally assigned to general principles of Union law. Yet, if Article 11 TFEU operates likes a general principle, it has not been formally recognized as such by the Court of Justice.

4. Article 11 TFEU as a General Principle of Union Law?

A. The rationale for a general principle of environmental integration

Article 11 TFEU is clear. It is the primary responsibility of the policymaking institutions, from the European Council to the European Central Bank (ECB), to integrate environmental protection requirements in the definition and implementation of Union's policies and activities, in accordance with the competences and powers they have under the Treaties. Recently, these institutions have sought to deliver on their constitutional obligation to respond to the growing environmental crises, namely climate change and biodiversity loss. The Court of Justice's inconsistency in upholding Article 11 TFEU has not prevented or hampered these efforts.

Nevertheless, the policy response does not exonerate the CJEU. If policymaking institutions fail to integrate environmental protection requirements, it becomes the responsibility of judges to enforce Article 11 TFEU. ¹²⁹ This is not a fictional scenario. The momentum sustaining the EU Green Deal policy agenda may be short-lived. Some of its measures may already be falling short of what is required for the protection of the environment. Others are being rolled back, not because they are inadequate for environmental protection, but because of short-term considerations that overlook environmental protection. The EU's policy response to the environmental crises may have been long delayed by the failure to fulfill the constitutional obligations deriving from the principle of environmental integration. Implementation and enforcement may also be lacking or inadequate, whether at Union or at Member State levels. ¹³⁰

The unprecedented rate and threat posed by climate change and biodiversity loss add on to the constitutional relevance of Article 11 TFEU. These environmental crises pose long-term, cross-border and systemic threats on the economy and society. The International Panel on Climate Change (IPCC), in charge of synthetizing and making accessible scientific evidence on climate change, has asserted in its latest report the irreversibility of climate change, and emphasized that: ‘Climate change is a threat to human well-being and planetary health. There is a rapidly closing window of opportunity to secure a liveable and sustainable future for all.’ ¹³¹ Mitigating climate change necessitates ‘rapid and far-reaching transitions across all sectors and systems’. ¹³² In other words, the integration of environmental protection requirements across sectors mandated by the Treaties is vital. Climate change further raises problems of intergenerational burden as it disproportionately affects young and future generations, although the KlimaSeniorinnen case of the European Court of Human Rights (ECtHR) also highlighted the higher mortality and lesser quality of life of the elderly that already results from climate change, and the human rights implications thereof. ¹³³

Even though policymaking institutions bear the primary responsibility to protect the environment and citizens from the harmful effects of environmental degradation, their action has long been, and continues to this day to be, insufficient to limit climate change and biodiversity loss. ¹³⁴ The dependence to fossil fuels and unsustainable modes of production and consumption is deeply entrenched in the economic system, which makes the transition to a sustainable economy a perilous undertaking. The tragedy of the horizon explains inaction in the face of climate change. ¹³⁵ Because the environmental crises are long-term problems, they exceed the typical horizons of those exercising political and economic power. ¹³⁶ Yet, once climate change becomes a defining issue for these actors, it will be too late to act given the irreversibility of such massive environmental degradation. Thus, evidence shows that the further climate action is delayed, the more difficult and costly it will be, not only to mitigate, or to adapt to, but also to compensate for the losses and damages caused by, climate change. ¹³⁷

Remedies against political inaction may be found before the courts, as a channel for accountability. Recent years have witnessed a remarkable rise in climate litigation. Private parties have brought claims against states and governments for their failure to mitigate climate change by invoking constitutional obligations and fundamental rights. The Urgenda case, notably based on Articles 2 and 6 of the European Convention of Human Rights (ECHR), marked the first successful climate challenge against a government. ¹³⁸ The success of Urgenda encouraged other claims, resulting in new precedents across Europe for environmental protection and climate action set by national constitutional courts. ¹³⁹ More recently, the ECtHR decided in KlimaSeniorinnen that Article 8 ECHR afforded a right of protection from the serious adverse effects of climate change that implies positive obligations on State Parties to take effective mitigation and adaptation measures to protect human life and health. ¹⁴⁰

Climate litigation has not spared the European Union. Yet both the General Court and the Court of Justice rejected in Carvalho claims directed against the Energy-Climate package adopted in 2018 to set reduction targets of greenhouse gas emissions, as claimants could not meet the Plaumann admissibility criteria to challenge EU legislation. ¹⁴¹ The CJEU did not examine the merits of the claims. Had it done so, there is no certainty as to how it would have responded given that the Treaties, unlike most constitutions of the Member States, do not provide for an enforceable fundamental right to a clean and healthy environment.

What the EU has, however, is Article 11 TFEU. The principle of environmental integration provides a clearly worded constitutional obligation long intended as such, even though it does not raise to the level of a fundamental right given the nature of the obligation it sets. If it is first and foremost the responsibility of policymaking institutions of the Union and the Member States (when implementing EU law) to uphold Article 11 TFEU, remedies against their failure must be sought before the CJEU, either directly or through preliminary references. It will be then the CJEU's responsibility to enforce the principle of environmental integration. By doing so, the CJEU may provide an avenue for accountability via a constitutional substitute to a fundamental right, critically absent from the EU's constitutional charter. Explicitly recognizing Article 11 TFEU as setting a general principle of EU law will provide a clear precedent for constitutional protection of the environment at EU level. It will give applicants arguments to mobilize in their quest for environmental justice and encourage the CJEU to be more vigilant about environmental protection. Consistently with the text and spirit of the Treaties, it will incite policymaking institutions to respect their obligation to integrate environmental protection requirements in EU law and policies while providing means to redress their failures to do so. Enforcing the principle of environmental integration will contribute to remedying the shortness of the political horizon, as well as to ensuring the adequacy of the policy response to the environmental crises. Its recognition as a general principle of Union law will bring the European Union back on par with most Member States and democracies beyond Europe that provide constitutional protections for the environment. ¹⁴²

B. The judicial baseline set by Mobility Packages and LivaNova

Like most general principles, ¹⁴³ Article 11 TFEU does not set a rule requiring a specific outcome, but it unambiguously provides for a generally applicable principle that must be operationalized by EU institutions and Member States. ¹⁴⁴ In this respect, Mobility Package and, to a lesser extent, LivaNova determine the minimal content of the principle of environmental integration entailed by Article 11 TFEU.

Firstly, both cases evidence the broad scope of the obligation to integrate environmental protection requirements. Following the text of Article 11 TFEU, this obligation applies from the definition of political choices in the legislation, as illustrated in Mobility Package, all the way down to enforcement. By ruling in LivaNova that corporate liability also covers environmental damages, the Court indeed applies Article 11 TFEU to enforcement by national courts. This is not unprecedented, ¹⁴⁵ but these grand chamber judgments confirm that the whole decision-making chain falls within the scope of application of Article 11 TFEU. As such, the environmental integration principle constitutes a positive obligation of constitutional nature that also applies to EU institutions, bodies, agencies and offices, as well as Member States. Failing to do so exposes them to litigation before the CJEU, whether through actions for annulment, infringement proceedings, actions for failure to act, or preliminary proceedings.

Secondly, Article 11 TFEU creates obligations even in the silence of secondary law. That much is clear from both cases. Even though the legislation in question in Mobility Package concerns internal market, social and transport policies without reference to environmental protection, it did not stop the Court to review its legality on the basis of Article 11 TFEU. Similarly, the Sixth Company Law Directive in question in LivaNova does not mention environmental damages but the Court interpreted the notion of liability extensively and referred to Article 11 TFEU as support for this interpretation. The same happened years earlier with the public procurement directive in Concordia Bus Finland. ¹⁴⁶ Hence, EU institutions, bodies, offices and agencies as well as national authorities should integrate environmental protection requirements when acting in accordance with EU law.

Thirdly, the Grand Chamber of the Court of Justice in Mobility Package highlighted the negative dimension of Article 11 TFEU by examining whether the legislation at stake would result in notable greenhouse gas emissions to determine their legality. In doing so, the Court effectively established that EU law cannot have for effect to undermine environmental protection. This third tenet is strikingly similar to the fragile rise of ‘Do No Significant Harm’ provisions in secondary law which bar measures with significant negative effect on the environment. ¹⁴⁷ The Court's finding is also close to the more distant but well-established do-no-harm principle of International environmental law. ¹⁴⁸

Fourthly, as a consequence of the negative obligation recognized in Mobility Package, Article 11 TFEU implies the necessity for European, as well as national authorities within the scope of EU law, to consider the environmental impact of their decisions. Indeed, if the legality of a decision depends on the environmental damage that it causes, it inevitably means that, prior to make a decision, public authorities have to assess the environmental impact that the decision will have. This obligation is consistent with the European Climate Law, which compels the Commission to review the consistency of EU and national policies as well as of any legislative proposal it introduces with the EU's climate objectives. ¹⁴⁹ It is also broadly consistent with EU law, which has long obliged environmental impact assessments for certain public and private projects. ¹⁵⁰

Fifthly, and by contrast, LivaNova, just like Concordia Bus Finland earlier, underlines the positive dimension of the principle of environmental integration. While both rulings in Mobility Package and LivaNova represent judicial strikes against environmental externalities, the latter also implies a positive obligation. That positive obligation is for European and national authorities to give full regard to environmental protection in decision-making, not just to prevent new damages, but to act against existing ones.

Together, Mobility Package and LivaNova set important precedents, both delivered by the Grand Chamber of the Court of Justice. They provide a clear compass for the integration of environmental protection requirements in EU law. And, more importantly, they recognize the nature of Article 11 TFEU as a clear, binding and enforceable constitutional provision akin to a general principle of Union law.

C. Fleshing out the general principle of environmental integration beyond existing case law

Even though the recent decisions of the Court of Justice provide a baseline and clarify the obligations that flow from the principle of environmental integration, there is more to Article 11 TFEU than what the Court of Justice recognized in the case law. This section makes suggestions for strengthening the effet utile of the principle of environmental integration.

The scope of Article 11 TFEU is broad. It requires environmental protection requirements to be integrated across all Union policies and activities, regardless of whether they fall under exclusive, shared or residual competences. ¹⁵¹ The comprehensive scope, expressed by covering both the Union's policies and activities, reflects the whole-of-government approach needed to address environmental crises. Furthermore, the whole decision-making chain falls within the scope of application of Article 11 TFEU. Environmental protection requirements must be integrated by EU institutions not only in their policymaking and lawmaking activities, but also when carrying out their responsibilities for applying, operationalizing and enforcing EU law. It also means that Article 11 TFEU must be respected by the European Commission and the Council in international relations. ¹⁵² The same applies for EU bodies, agencies and offices as well as Member States within the scope of Union law. In this last respect, the Court of Justice has, in Åkerberg Fransson, accepted an extensive, albeit controversial, interpretation of ‘implementing Union law’ under Article 51(1) CFR that may apply by analogy in the context of Article 11 TFEU. ¹⁵³ In other words, the environmental integration principle constitutes a positive obligation of constitutional nature for EU institutions, bodies, agencies and offices, and Member States. They are responsible for integrating environmental protection requirements across the range of Union policies and activities and, depending on their competences, in the definition and implementation of Union law.

Article 11 TFEU sets both procedural and substantive obligations. A prerequisite implied by the provision is for the EU and its Member States to consider environmental protection wherever relevant. If environmental protection requirements are not taken into account in decision-making, there is indeed little chance that they become integral to the Union's policy. While paying full regard to environmental protection is a necessary step, it is not sufficient by itself. Article 11 TFEU requires the integration of environmental protection requirements, that is, the adoption and implementation of measures to meet environmental protection requirements. To determine whether environmental protection requirements are met or should be addressed, an impact assessment of the environmental effects of the measure or the policy is necessary. This is clear from the Court of Justice's grand chamber judgment in the Mobility Package, as the assessment of the negative environmental effects determines the legality of the legislation. The European Climate Law also introduces obligations for the Commission to assess and report the impact of the laws and policies of the EU and its Member States on the EU's climate objectives. ¹⁵⁴ In other words, the procedural obligations entailed by Article 11 TFEU entail the systematic consideration and, wherever relevant, integration of environmental protection requirements supported by impact assessments.

The second stage of the analysis should focus on the adequacy of the environmental protection requirements. The act of integration is by itself not sufficient. On the one hand, environmental protection requirements should appropriately cover the scope of Union law and policies in order to prevent any loopholes. On the other hand, requirements should ensure environmental protection, consistently with sustainable development. Integrating environmental protection requirements means that environmental protection cannot be simply an option or a faculty, but that it is supported by mandatory obligations.

Accordingly, Article 11 TFEU sets an obligation of result. While environmental protection requirements are not defined – in accordance with the principled nature of Article 11 – benchmarks for the integration of environmental protection may be found in EU law as well as international law to which the Union subscribed. Article 11 TFEU refers to the objective of sustainable development which governs the internal market in accordance with Article 3(3) TEU. It is helpful to determine the ambition of environmental protection requirements, as mere development cannot be considered sustainable in the present context of broken planetary boundaries and imperilled future for both present and upcoming generations. ¹⁵⁵ Both under Article 37 CFR and in Article 3(3) TEU in the province of sustainable development, ‘a high level of protection and improvement of the quality of the environment’ specify the value of the environmental protection requirements under Article 11 TFEU. ¹⁵⁶ While Article 37 CFR is only a ‘principle’ under the Charter's (admittedly) confusing taxonomy of rights and principles, it means that it is applicable, and justiciable, wherever Article 11 TFEU is respected.

The objectives of environmental protection have been further specified by the EU legislature so as to guarantee a sustainable development. The European Climate Law introduces binding climate targets for the European Union. Similarly, the Nature Restoration Law sets binding restoration objectives of land and marine ecosystems with the ultimate aim to cover ‘all ecosystems in need of restoration by 2050’. ¹⁵⁷ As such, the European Climate Law and Nature Restoration Law provide concrete benchmarks for environmental protection requirements, consistently with Article 3(3) TEU and Article 37 CFR. In addition, the European Union is a party to the United Nations agreement on Biodiversity Beyond National Jurisdiction (BBNJ), which introduces protective measures for marine biodiversity in the high seas. ¹⁵⁸ Other measures of international law, such as the Kunming–Montreal Global Biodiversity Framework or the 2030 Sustainable Development Agenda, set a number of targets and objectives for sustainable development and environmental protection that the European Union has endorsed. It is in this perspective, taking into account the objectives of environmental protection set in primary and secondary law as well as in international law, that environmental protection requirements should be set and assessed. Such objectives should guide the Court of Justice with respect to all three functions of the general principle of Union law set in Article 11 TFEU, notably when interpreting an act to ensure that environmental protection requirements are integrated in the implementation of Union policies. The objectives of environmental protection must serve as benchmarks for the Court of Justice to examine whether the EU and its Member States observe the law.

Besides, the CJEU should give precedence to the general principle in a conflict of rules. ¹⁵⁹ Concretely, the principle of integration—even if it is itself not a fundamental right— entails that the protection of the environment can derogate to, and even in certain cases prevail over, conflicting fundamental freedoms and fundamental rights with due regard to the principle of proportionality. There are some precedents in this respect, ¹⁶⁰ including, as discussed above, on the basis of the principle of integration. Article 11 TFEU provides a solid basis for furthering the case law. ¹⁶¹ The Court of Justice may give precedence to environmental protection by adopting the reasoning it laid down in AGET Iraklis. The Court balanced in this case the freedom of establishment and the right to conduct a business under Article 16 CFR with the objectives of social protection and ‘a high level of employment’ derived from Article 3(3) TEU and the ‘social’ horizontal clause of Article 9 TFEU. ¹⁶² The Court of Justice did so by considering the context of an acute economic crisis and high level of unemployment. By analogy, and considering the stronger formulation provided by Article 11 TFEU, the Court of Justice should give precedence to environmental protection in the current context of acute environmental crisis. ¹⁶³

Finally, it is necessary to underline the negative dimension of the principle of environmental integration. By mandating the integration of environmental protection requirements, Article 11 TFEU mechanically entails that Union law and policies cannot be a conduit for harming the environment. This is not surprising and, when reviewing the legality of Union law in the recent Mobility Package case, the Court of Justice investigated whether the legislation would generate significant greenhouse gas emissions. ¹⁶⁴ The growing acceptance and incorporation of the ‘do no significant harm’ obligation into EU law support Article 11 TFEU, ¹⁶⁵ as this notion provides a useful synthesis of the negative dimension of Article 11 TFEU. It is also consistent with the objective of sustainable development set in Article 3(3) TEU and echoes international environmental law. ¹⁶⁶

Furthermore, Article 11 TFEU should be read as prohibiting regressions in environmental protection. ¹⁶⁷ This can be inferred from a joint reading with Article 37 CFR and Article 3(3) TEU which provide for ‘a high level of environmental protection and the improvement of the quality of the environment’ (emphasis added). Read together, they imply an obligation of non-regression in environmental protection. The constitutional obligation to integrate environmental protection requirements across EU law means that such requirements cannot be taken away, or the integration principle would be defeated. Once environmental protection requirements are provided, they must abide by Article 37 CFR by not only achieving a ‘high level of protection’ but also contribute to ‘the improvement of the quality of environment’. ¹⁶⁸ As such, environmental protection requirements can only be substituted with at least equivalent norms in their object and environmental effects. The weakening of law and policies integrating environmental protection requirements would thus be contrary to both Article 11 TFEU and Article 37 CFR. An obligation of non-regression would also be consistent with the Union's international obligations, as the Paris Agreement itself introduces a ratchet clause to prevent regression in climate action. ¹⁶⁹ An obligation of non-regression could prevent short-termist actions such as weakening environmental conditions in the Common Agricultural Policy, ¹⁷⁰ or watering down environmental law under the guise of simplification. ¹⁷¹

5. Conclusion

Amidst unabated climate change, rising biodiversity loss and aggravated environmental crisis, it is high time that the principle of environmental integration be unearthed. Article 11 TFEU represents the sole horizontally applicable and justiciable constitutional protection provided by the Treaties. And despite a strong wording, a clear history and purpose and a distinctive relevance, it has been largely overlooked by the constitutional doctrine, the case law and, to some extent, institutional practice. Still, the European Green Deal represents a renaissance of the spirit, if not the letter, of the principle of environmental integration, and Article 11 TFEU remarkably reappeared in two recent grand chamber judgments of the Court of Justice. This represents a unique opportunity to admit the principle of environmental integration for what it should be and is in all but name: a general principle of Union law.

Already, Article 11 TFEU fulfills the three functions generally performed by general principles of Union law. It has been an aid to the CJEU in interpreting Union law. It has filled normative gaps in Union law. And most recently with the Mobility Package case it has been admitted as a ground for legal review. It was also used in non-traditional ways, including to justify derogations to fundamental freedoms. As a result, there are ample precedents for the Court of Justice to uncover the general principle of Union law enshrined in Article 11 TFEU.

Numerous reasons further advocate for this recognition. While the constitutions of Member States and, increasingly albeit indirectly, the ECtHR protect individuals’ right to live in a clean and safe environment, the principle of environmental integration represents an autonomous principle of Union law that purports a whole-of-government approach to the environmental crises supported by the relevance of the supranational level. It is not a fundamental right, but it includes both procedural and substantive obligations related to environmental protection that are incumbent on the Union and its Member States when implementing Union law. And it is consistent with the overarching Union's objective of sustainable development that protects present and future generations from damaging short-term political considerations.