Climate Change at the Forefront of the Structural Transformation of International Law

The ICJ’s advisory opinion on climate protection has far-reaching implications – both for climate action and for the entirety of (environmental) international law. The Court was faced with a complex task. Amid vigorous debates over the efficacy and relevance of international law, it was entrusted with the crucial task of precisely defining and reaffirming its capacity to guide state conduct in tackling one of the most urgent issues of our era. It has largely succeeded in doing so – even though the advisory opinion at times reflects a cautious, minimalist approach (see separate opinion of Judge Aurescu, para. 1), and many aspects remain vague and will require further clarification through future legal proceedings.

The advisory opinion sends a clear signal: States are obliged under international law to combat – the scientifically well-proven (paras. 72-87) – anthropogenic climate change. National contributions under the Paris Agreement are subject to judicial scrutiny. While many aspects of implementation remain within the realm of political discretion, the Court outlines the legal framework and emphasizes that climate protection is not merely a matter of political will but also a legal obligation (e.g. paras. 213, 237-239, 242-249, 270, 306). It is now clear that states are bound by customary and treaty-based obligations of prevention and due diligence to define and register national climate contributions that, collectively, are capable of limiting global warming to 1.5°C above pre-industrial levels (as of 1990). These obligations stem not only from sources of international environmental treaty and customary law but also from international human rights norms. The right to a healthy, clean, and sustainable environment is deemed inherent to all human rights – a finding that breaks with the long-standing anthropocentric understanding of human dominion over nature. Overall, climate change is treated with a view to its cross-cutting impact on other ecosystems, such as the oceans, and on human beings. The integrated interpretation of these different sources of law not only implies that states cannot easily evade their treaty obligations by withdrawing from the Paris Agreement, but also that these obligations are reinforced through interpretation in light of enhanced due diligence requirements under general international law. The need for multilateral cooperation is reflected in the Court’s interpretation of the relevant environmental law obligations as erga omnes in order to address climate change as a common concern of humankind. 

What does this advisory opinion mean for international (environmental) law? We argue that it both reflects and advances ongoing structural and systemic transformations by shaping a legal order that is integrative, rooted in multilateral cooperation, ecologically oriented, and increasingly reaches into the domestic sphere—traditionally shielded by state sovereignty—by explicitly, though indirectly, addressing the conduct of private actors. The advisory opinion affirms that the protection of the climate system constitutes a legal interest under customary international law (paras. 274-279). In doing so, the Court advances the ongoing “ecologisation” of international law. This shift reinforces the normative foundation for planetary welfare and highlights the collective obligations and shared responsibility of the international community of States, thereby safeguarding the climate system as a global commons in the interest of present and future generations.

With a view to these developments, this symposium will put emphasis on the opinion’s systemic and structural – interpretative and actor-related – implications for international law and pursue a comparative approach to yield initial insights into the normative function of advisory opinions and their influence on the international legal order. It is this very specific perspective from which our symposium aims to contribute to and converse with the growing body of early commentary (see for instance here) and carefully curated blog-debates (for example by our colleagues from the Verfassungsblog in cooperation with the Sabin Centre). 

The contributions to the symposium are broadly structured into three thematic clusters. The first cluster focuses on the advisory opinion’s interpretation of various subfields of international law and explores its potential to foster a systemic integration of climate obligations and these legal domains (I.). The second cluster investigates the advisory opinion’s potential impact on the ongoing structural transformation of international environmental law (II.). Indeed the opinion addresses four foundational issues – some might say fault-lines – of that transformation, namely the recalibration of international law’s purpose towards the protection of global environmental commons and the interpretation of international law as a coherent body of law oriented towards that end (II.1), the illusive public/private divide (II.2), the epistemic authority of science in international law and governance (II.3), and the continued negotiation of a postcolonial international legal order (II.4). The third cluster undertakes a comparative analysis of the three recent advisory opinions on climate matters, with particular attention to the specific role such opinions play in the development of international climate law (III). Here is a cursory overview of the different perspectives that the symposium brings into conversation:

I. The Advisory Opinion and a Systemic Integration of IL through Climate Change? 

‘[t]he Court considers that the argument according to which the climate change treaties constitute the only relevant applicable law cannot be upheld and finds that the principle of lex specialis does not lead to a general exclusion by the climate change treaties of other rules of international law’ (para. 171).

With this statement, the advisory opinion sends a clear signal: States are obliged under international law to combat anthropogenic climate change. These obligations do not only flow from climate change treaties, but also from a broad spectrum of international legal sources: custom (see the blog post of Phillip Paiement and Corina Heri), the law of the sea (see the blog post of Rozemarijn Roland Holst) and human rights (see the blog posts of Helen Keller and Malavika Rao). The Court articulates a seemingly coherent legal framework composed of the ‘most directly relevant’ norms, from which a set of complementary obligations can be derived. As a result, the Court identified ‘a single set of compatible obligations’ (para. 165). It acted as architect of an integrated international order in respect of climate change obligations (see the blog post of  Denise Köcke and  Andrej Lang).

As far as the climate change treaties themselves are concerned, the ICJ intervened on a number of intensely debated questions. It clarified the relationship between the existing climate change treaties (paras. 194,225) and strengthened the role of COP and CMA decisions by acknowledging their legal bindingness (para. 184) by considering ‘the 1.5°C threshold to be the parties’ agreed primary temperature goal […] under the Paris Agreement’ (para. 224). More importantly still, the Court clarified the obligations arising from the Paris Agreement, especially regarding mitigation, showing that the discretion of parties in defining their nationally determined contributions (NDCs) and in implementing them is limited by a set of concrete obligations of conduct and of result which must be exercised with stringent due diligence (see blog post of Christina Voigt). Accordingly, the Court has subjected these actions to its judicial scrutiny.

II. Structural Changes of International (Environmental) Law

1. The Proceduralisation of International Environmental Law and a Turn to the Future driven by a Normative Vision of a Cooperative Pursuit of Shared Interests.

The advisory opinion frames multilateralism as a necessary element of an effective response to global environmental challenges and legally insists on the institutionalized exchange among states (paras. 301, 304, 307-308). The Court strengthens institutionalized cooperation by assigning independent legal value (para. 140), under Article 31(3)(a) of the Vienna Convention on the Law of Treaties, to agreements reached at COPs (para. 184). The emphasis on a self-standing duty to cooperate – coupled with the need for multilateral solutions – highlights that the cooperative character of environmental international law is firmly upheld despite recent regressions. 

The cooperative and interactional approach that the court endorses at the institutional level, is mirrored at the material level by the ubiquity of due diligence throughout the advisory opinion. In fact, the core of the obligations that the Court identifies require parties to act with due diligence – whether it concerns the obligation to prepare NDCs under Article 4(1) of the Paris Agreement, the duty to pursue domestic mitigation measures under Article 4(2), or other obligations of conduct enshrined in the Paris Agreement. The same standard also underpins customary international duties, such as the obligation to prevent significant environmental harm and the duty to cooperate (see the blog post of Jutta Brunnée). Both – the institutional and material element – represent a deepened proceduralisation of international environmental law, meaning that cooperation and due diligence are primarily effectuated through established procedures (para. 295). 

These forms of proceduralisation are also a legal response to climate change’s futurity, that is to say that regulating climate change means pursuing a vision of the future through legal means. While there are many areas of international law that are characterised by international law’s turn to the future, climate governance is one of the more prominent examples. The ICJ’s advisory opinion now marks the latest effort to operationalise this regulatory turn to the future (see the blog post of Jochen Rauber). Most strikingly the Court recognises intergenerational equity as interpretative principle: 

‘[…] intergenerational equity is a manifestation of equity in the general sense and thus shares its legal significance as a guide for the interpretation of applicable rules.’
(para. 157)

The future-oriented regulatory turn envisaged by the Court is driven by a normative vision of the cooperative pursuit of common interests, casting States as trustees of the atmosphere and subjecting carbon sovereignty to justification under international law (see the blog post of Jannika Jahn and Nele Suchantke).

2. Reconciling Conflict Lines Between Global North and South

The Court turns to the distinction between developed and developing countries, tackling the conflict between the major emitting states and the vulnerable states that have contributed least to climate change (see the blog post of Lovleen Bhullar). The participation of numerous small and highly vulnerable states from the Global South — many of them engaging with the Court for the first time — underscores the significance these states attributed to the proceedings as part of their broader pursuit of climate justice (see the blog post of Lillian Robb and Vishal Prasad). The Court acknowledges the significant contribution of industrialized countries to climate change (cf. para 150) and signals that states refusing to act on climate protection may incur international responsibility (para. 421). Whether this also extends to historical emissions is left open. 

By emphasizing equity and the principle of common but differentiated responsibilities and respective capabilities as interpretative principle (para. 151), the Court makes clear that it is seeking fair and flexible answers to the question of who should bear the cost of climate protection. This flexibility becomes particularly tangible in the Court’s pronouncement that 

‘the addition of the phrase “in the light of different national circumstances” […] does not change the core of the principle of common but differentiated responsibilities and respective capabilities; rather, it adds nuance to the principle by recognizing that the status of a State as developed or developing is not static. It depends on an assessment of the current circumstances of the State concerned.’
(para 225, emphasis added). 

Thus, the Court follows the steps already taken by the Paris Agreement toward a dynamic differentiation capable of reflecting shifting realities. 

While the Court did take note of the potential legal implications of climate change for the right to self-determination, it refrained from elaborating on them — notwithstanding their demonstrated significance in the ILC Study Group’s recent report on sea-level rise in relation to international law (see the blog post of Dave-Inder Comar).

3. The Integration of Science into Law 

The Court addresses the epistemic authority of science in international law. The advisory opinion relies on science for the formation of normative benchmarks (see the blog post of Katalyn Sulyok). In order to illustrate the centrality of (climate) science for international law’s regulatory grip on climate change, the Court begins by telling the (hi)story of the emergence of international environmental and climate law as a reaction to and a product of the solidification of scientific knowledge on environmental degradation (Section on ‘General Context and Scientific Aspects’, paras 50-71). A substantive part of the advisory opinion deals with establishing the scientific consensus on climate change (paras. 72-87). For this, the ICJ relies ‘primarily on the IPCC reports, which participants agree’ (para. 74) ‘constitute comprehensive and authoritative restatements of the best available science about climate change’ (para. 284). In doing so the Court fervently strengthens the epistemic authority of the IPCC. 

4. International Law beyond the State: A Gradual Softening of the Public/Private Dichotomy

Moreover, the Court addresses the intricacies of the public/private divide. 

Corporations are major polluters as well as governance actors in matters of climate change. Hence, their responsibility   for fostering climate protection has become an object of research. Climate proceedings have been filed against corporations at the national level. In line with prevailing doctrine and jurisprudence, the Court approaches this topic in an orthodox manner in its Opinion by not directly addressing private actors’ (legal) climate responsibilities. Nevertheless the Court explicitly called on states to regulate private conduct (see the blog post of Harro van Asselt). The Court acknowledges that ‘the activities in question are mostly carried out by private persons or entities’ (para. 252, quoting the ITLOS advisory opinion para. 236). Consequently, it finds that the duty of due diligence includes the regulation of private sector activities (paras. 252, 276, 282, 403, 428) and states that the “[f]ailure of a State to take appropriate action to protect the climate system from GHG emissions — including through fossil fuel production, fossil fuel consumption, the granting of fossil fuel exploration licences or the provision of fossil fuel subsidies — may constitute an internationally wrongful act which is attributable to that State” (para. 427) (see the blog post of Phillip Paiement and Corina Heri). It nevertheless does not go as far as the IACtHR in its advisory opinion which spelled out in greater detail what states must do to regulate companies’ activities in combating the climate crisis (see the blog post of Harro van Asselt). Nevertheless, the ICJ’s Advisory Opinion might still cautiously strengthen international (environmental) law’s  transformative function — catalyzing structural shifts in the energy and economic spheres.

Another aspect of the public/private divide that is constantly re-negotiated within environmental governance are modes of public participation. In that regard the advisory opinion shows how civil society organisations and individuals may shape the international legal order. Vanuatu, the state that initiated the advisory opinion, was counselled by NGOs and students. And even though the Court formally stuck to its procedural rules, allowing only States and international organisations to present written or oral statements, the proceedings still reflect how civil society and individuals may indirectly partake in the shaping and interpretation of legal vocabulary and standards (see the blog post of Lillian Robb and Vishal Prasad).

III. Comparative Perspectives: On the Functions of Advisory Opinions, Temporalities, and Narratives

The final cluster of our blogpost symposium exploring comparative perspectives between the three advisory opinions on the topic of climate change is warranted by the fact that the ICJ intensively engaged in an inter-judicial dialogue with ITLOS and the IACtHR through references to their respective advisory opinions. Admittedly the ICJ does not limit its engagement to these two institutions but draws on a whole range of institutions. Nevertheless, the ICJ seemed intent to produce an advisory opinion that is visibly complementary to the two others. This sustained inter-judicial dialogue not only fosters normative integration across jurisdictions, but also contributes to the emergence of a more coherent body of international climate law through the advisory jurisdiction of international courts and tribunals (see for instance the blog post of Khaled El Mahmoud). 

More generally, these three consecutive advisory opinions merit a more detailed investigation into the evolving normative function of advisory opinions and their normative influence on the development of the international legal order, specifically in relation to climate change. Although formally non-binding, this latest ICJ advisory opinion constitutes a landmark contribution to international climate law, underscoring the potential systemic relevance of these instruments. Through persuasive legal reasoning, careful management of stakeholder expectations, and robust engagement with the jurisprudence of other international bodies, the Court has laid a normative foundation that may guide future litigation and policymaking efforts in this existentially significant area (see the blog post of Andreas Kulick). 

For instance, both the ICJ and the IACtHR affirm the justiciability of climate harm and the applicability of international legal responsibility to climate-related breaches albeit with distinct reasoning. While the ICJ put an emphasis on strengthening the doctrinal foundation of climate obligations, the IACtHR focussed on enhancing the accessibility and effectiveness of climate justice through procedural innovations and rights-based reasoning (see the blog post of Juan Auz).

Finally, all three opinions share certain narratives and an approach to the temporality of international climate law that focuses primarily on the future. By embracing a specific understanding of climate change’s temporal situatedness, through the creation of temporal boundaries of the phenomenon of climate change, the advisory opinions delimit the jurisdictional scope for international law’s grasp on the climate and strongly influence our climate ‘imaginaries’ (see the blog post of David Scott). It is also at this point that the narratives embraced by the advisory opinions play an important role: Not only because they adopt a doomsday, now-or-never crisis narrative ( i.e. para 456). Not only because they reveal the role that these advisory opinions ascribe to themselves as historic events in the Courts’ histories (i.e. para 456) or because they narrate a story of progressive development of international environmental law in unison with – and in response to – scientific progress (Section on ‘General Context and Scientific Aspects’, paras 50-71).  But also because the ICJ’s Advisory Opinion and its proceedings have acted as an archive of narrated microhistories which records the lived experiences of those most affected by climate change and which compensates the absence of an in concreto assessment by the Court   (see blogpost by Rashmi Dharia).

IV. Conclusion

In conclusion, this symposium aims to demonstrate that, from the perspective of international legal scholarship, the ICJ’s Advisory Opinion should be understood as more than a potentially ground-breaking intervention in the field of climate change. Rather, it constitutes a significant catalyst in the ongoing structural transformation of international law itself.