Climate Change Litigation: International Legal Perspectives

Abstract

Climate change litigation is rapidly gaining importance as a legal tool to induce action against the causes and effects of climate change. This Special Issue examines the rapidly evolving area of climate change litigation through the lens of international law. While most climate change litigation occurs before national courts, international law plays a key role in shaping the arguments of claimants, the obligations of respondents, and the available remedies. Not only is climate litigation being used to enforce existing international human rights and environmental obligations, but it also drives the development of new understandings of international legal norms in the context of climate change. The contributions to this Special Issue highlight emerging legal debates, doctrinal developments, and the interaction between international law and other areas of law in shaping States’ and corporations’ climate responsibility through litigation.

1 Introduction

Climate change litigation is a growing phenomenon, leveraging judicial power to compel action to mitigate climate change or address its impacts.¹ It is rapidly gaining in importance as a legal tool to induce action against the causes and effects of climate change.² Climate change lawsuits can be filed against governments, corporations or other entities to enforce environmental legislation, hold polluters accountable and/or protect the human rights of those affected by climate change. In recent years, litigation has emerged as an important supplement to climate change negotiations, especially where political and regulatory responses have proven insufficient.³ It also raises public awareness, mobilises public opinion and thereby influences policy decisions.⁴ But climate litigation also raises rather fundamental questions about the ‘trias politica’ and the role of courts versus legislators and governments.⁵

The present special issue seeks to explore this emerging area of legal action from the perspective of international law. It looks at how courts and tribunals—international, national and regional—interpret international legal obligations, develop new principles and push the boundaries of existing legal frameworks to respond to what the International Tribunal on the Law of the Sea (ITLOS) and the International Court of Justice (ICJ) respectively described as an ‘existential threat’⁶ and an ‘existential problem of planetary proportions’.⁷ The contributions in this special issue illustrate how international law interacts with, and is shaped by, the diverse forms of climate change litigation now evolving in various national and international fora.

2 The Theme of the Special Issue

The proliferation of judicial and quasi-judicial cases in the area of climate change is indicative of the increasing urgency to act as identified by climate science as well as the failure of many States and companies to take sufficient mitigation and adaptation action. Litigation has become a key tool for citizens, NGOs and affected communities to press for stronger climate measures. Notable cases such as Urgenda Foundation v. State of the Netherlands,⁸Milieudefensie v. Royal Dutch Shell,⁹VZW Klimaatzaak v. Kingdom of Belgium and Others¹⁰ and KlimaSeniorinnen Schweiz v. Switzerland¹¹ illustrate how courts can be pivotal in holding both public and private actors accountable. These cases highlight the role of climate change litigation in two important respects. First, litigation is being used to enforce existing environmental and human rights obligations, grounding climate protection in legal norms that already have binding force.¹² Second, climate litigation has also become a driver of new norms, pushing courts to articulate new understandings of responsibility, causation and intergenerational equity in the context of climate change.¹³

While much climate change litigation primarily occurs before national courts, international law has a central role to play in shaping the arguments of claimants, the obligations of respondents and the available remedies. International law can be seen as the overarching normative framework within which climate protection obligations are defined.¹⁴ At the same time, international law offers specific fora for claimants to have access to adjudication and to request advisory opinions. This normative and institutional role of international law can be seen in the following areas.

First, international human rights law has emerged as a major avenue for climate change litigation.¹⁵ The judgement of the European Court of Human Rights (ECtHR) in KlimaSeniorinnen Schweiz v. Switzerland reflects an important milestone, in that inadequate climate action was recognised to amount to a violation of human rights, in particular the right to private and family life.¹⁶ Similar human rights-based reasoning was advanced before the UN Human Rights Committee (HRC) in Teitiota v. New Zealand, leading to a recognition by the HRC that climate change poses one of the most ‘pressing and serious threats’ to the right to life.¹⁷ The Inter-American Court of Human Rights (IACtHR), in its Advisory Opinion on the Climate Emergency and Human Rights, derived from the fundamental rights to life, personal integrity, and health a jus cogens prohibition on anthropogenic conducts that could irreversibly harm the equilibrium of our planetary ecosystem that makes human life possible.¹⁸ The Advisory Opinion of the ICJ on the Obligations of States in Relation to Climate Change found that ‘States have obligations under international human rights law to respect and ensure the effective enjoyment of human rights by taking necessary measures to protect the climate system and other parts of the environment’.¹⁹ These developments show how international human rights law is being harnessed to frame climate change not only as an environmental issue but also as a matter of fundamental rights.

Second, new litigation possibilities under the UN Convention on the Law of the Sea (UNCLOS) have arisen due to the central role of the ocean in climate change. Not only are many of the effects of climate change evident in the ocean, such as rising sea levels, acidification and warming, but the ocean is also essential in mitigating the effects of climate change due to its capacity to absorb carbon and excess heat in the climate system.²⁰ While UNCLOS makes no explicit mention of climate change, scholars have long argued that greenhouse gases are to be seen as marine pollutants.²¹ This view was confirmed in the recent Advisory Opinion of the ITLOS, requested by the Commission of Small Island States on Climate Change and International Law. Interpreting UNCLOS coherently with the climate treaties, ITLOS clarified that States Parties have obligations under UNCLOS to adopt and enforce laws and regulations to prevent, reduce and control marine pollution resulting from greenhouse gas emissions.²² More specifically, the Tribunal recognised the obligation to protect and preserve the marine environment from the effects of climate change and ocean acidification.²³ By highlighting the stringent due diligence obligation arising from this, given the high risks of serious and irreversible harm to the marine environment from greenhouse gas emissions,²⁴ and extending it to States’ obligations with respect to non-State actors,²⁵ ITLOS has established the protection of the oceans as an essential element in the toolbox that petitioners can deploy in climate change litigation.

Third, climate change litigation is fleshing out established principles of international environmental law,²⁶ such as sustainable development,²⁷ the precautionary principle,²⁸ the principle of common but differentiated responsibilities,²⁹ and the duty to prevent transboundary harm.³⁰ Foundational treaties, such as the United Nations Framework Convention on Climate Change (UNFCCC) and the Paris Agreement, not only articulate States’ commitments to address climate change but also reflect core environmental law principles. Courts are being called upon to translate these abstract concepts into enforceable obligations, thereby testing their strength and determining their limits in the context of climate threats. The open-textured nature of these principles of international environmental law is susceptible to innovative interpretations, making them fertile ground for the evolution of international climate jurisprudence.

3 Contributions to This Special Issue

The contributions to this special issue aim to enrich the discourse on climate change litigation by viewing it through the lens of international law, highlighting its multifaceted role. The special issue is based on the Ius Commune Workshop which took place in November 2024 in Utrecht, as part of the Ius Commune research programme on ‘Constitutional Process in the Global Legal Order’. The selected contributions highlight emerging legal debates, doctrinal developments and the interaction between international law and other areas of law in shaping States’ and corporations’ climate responsibility through litigation.

The special issue starts with the contribution by Dominic Coppens and Nicolas Lockhart, who discuss the three recent landmark advisory opinions of, respectively, ITLOS, the IACtHR and the ICJ. The article brings together the courts’ core mitigation-related findings, thereby identifying similarities and differences among them, and explores the implications of these opinions for future climate action. According to the authors, despite differences in the questions put before each court, the legal instruments they addressed, the participants before them, and each court’s legal tradition, the opinions show significant convergence, albeit with some notable divergences. In essence, the courts concluded that international law imposes stringent yet differentiated mitigation obligations on all States to address climate change, both individually and collectively. The authors demonstrate how the courts have woven together various legal sources to create a coherent tapestry of complementary mitigation-related obligations. They conclude that the high level of substantive convergence across the three advisory opinions (including the lack of dissenting opinions) reinforces their authority, that States, in order to meet their international obligations, will have to adopt and enforce ambitious mitigation action, and that the opinions will likely lead to increased litigation.

In a second contribution, Roman Girma Teshome examines the determination of victim status as an admissibility criterion in rights-based climate change litigation. Teshome critically analyses the ECtHR’s interpretation of the criterion of victim status in KlimaSeniorinnen, in which the Court appeared to have adopted a stringent criterion for the determination of victim status for climate change cases partly to avoid actio popularis. On this basis, Teshome’s article explores alternative perspectives with which to establish victim status in a way that accommodates the unique characteristics of climate change without fully compromising the restrictive purpose of the admissibility criterion. For example, Teshome argues that the intersectionality approach can and should inform the determination of victim status. The intersectionality lens would allow human rights bodies to consider the differentiated impacts of climate change on individuals, depending on their identities and socio-economic situations. Teshome submits that this should be combined with an explicit recognition of a climate exception to the prohibition of actio popularis, which would offer not only clarity but also legitimacy to the reasoning of the ECtHR in rights-based climate cases.

Antoine De Spiegeleir’s contribution explores the broader significance of the ECtHR’s reasoning in KlimaSeniorinnen for international law, beyond the framework of the European Convention on Human Rights (ECHR). De Spiegeleir points out that KlimaSeniorinnen became a point of reference that one cannot avoid in international human rights law arguments concerning climate and climate-related harms. De Spiegeleir analyses how KlimaSeniorinnen contributed to the law of State responsibility under international law by, for example, unequivocally rejecting the ‘drop in the ocean’ and ‘but for’ arguments typically invoked by States to avoid their responsibility. The ECtHR also effectively raised the due diligence standard by providing details on how the failure to adopt and effectively implement a climate mitigation plan would lead to a breach of human rights obligations. Furthermore, De Spiegeleir highlights that the ECtHR, by taking into account the emissions produced abroad for goods and services consumed in Switzerland, challenged the territory-centredness of international human rights law with regard to climate change. More broadly, the ECtHR’s reference to a wide range of international binding and non-binding materials augmented their relevance in the broader interpretation and discussion of human rights in countering climate change.

Beichen Ding’s contribution addresses the extraterritorial climate change obligations and their implications for unilateral climate-related trade measures. Ding examines the two broad bases of extraterritorial climate obligations, namely, obligations arising from the extraterritorial application of human rights and environmental law, and obligations intrinsic to the global character of climate mitigation. On the basis of the analysis of these two grounds for extraterritorial obligations, Ding analyses the implications of these extraterritorial obligations for the permissibility of unilateral climate-based trade measures. Ding observes that unilateral trade measures may be justified under the framework of the World Trade Organization (WTO) if such measures align with other international obligations, meaningfully contribute to global climate objectives, and are in line with the principles of fairness and proportionality.

Finally, Isabela Keuschnigg and co-authors’ contribution focuses on corporate climate change litigation and critically examines the development of corporate responsibility for reducing Scope 3 emissions. Scope 3 emissions refer to the indirect greenhouse gas emissions resulting from the activities of a company’s suppliers and product users in the company’s value chain. The authors have analysed 12 judicial and quasi-judicial cases to understand the treatment of Scope 3 emissions in cases concerning a company’s climate mitigation actions. Importantly, the analysis of the cases reveals that there is growing recognition of corporate responsibility for Scope 3 emissions. While it has been challenging to translate this general responsibility into a specific emissions reduction target, the authors argue that the efforts to improve reporting standards for Scope 3 emissions may provide clearer guidance for future climate change litigation.

4 Conclusion: Climate Change Litigation as an Instrument of Change

As climate change impacts intensify and legal responses continue to evolve, the growing body of jurisprudence generated through climate change litigation provides a promising avenue for strengthening the climate regime.

First, climate change litigation serves to clarify the rights and obligations of States and corporate actors in this area. Courts and tribunals are increasingly asked not only to apply the law but also to interpret and even develop it. In this way, climate change litigation has begun to give rise to new understandings of State and corporate responsibility, causation, due diligence and equity, among others. Second, litigation serves to spur climate change mitigation by exerting pressure on both governments and corporations to align their actions with international climate commitments, even in the absence of strong enforcement mechanisms in the core climate treaties.

However, the transformative potential of climate change litigation is not without risks, and a word of caution is called for when reflecting on the role of courts in this regard, as indicated supra. Scholars have warned that the judicialisation of climate governance may threaten multilateral consensus-building through climate negotiations.³¹ Further, expansive normative developments through climate litigation that lack a firm foundation in treaty provisions may undermine the legitimacy of judicial rulings and cause compliance deficits.³² While landmark judgements and advisory opinions in climate change litigation may draw much attention and exert compliance pull, their enforceability is not guaranteed.³³

As a result, climate change litigation is best seen as a useful but not sufficient instrument of change in the fight against climate change. It has great potential to drive the evolution of legal norms, public policy and corporate conduct, but also faces structural and political constraints that may blunt its transformative force.