In its long-awaited advisory opinion on climate change, the International Court of Justice (ICJ) made a range of landmark findings on States’ obligations to address the climate crisis and the consequences of failing to do so. The pronouncements from the world’s highest court will now serve as immediate authoritative guidance to judiciaries across the globe. Accordingly, the opinion has the potential to alter the trajectory of climate change litigation, including cases concerning corporate accountability, fossil fuels permitting, and novel disputes between States (as other contributions in the Symposium will address). 

One major area of climate litigation that the advisory opinion will impact is “government framework” litigation – that is, cases that challenge governments’ weak mitigation ambition (so-called “Ambition Gap cases”) or failure to implement measures to meet their targets (so-called “Implementation Gap cases”) (for more, see here). These cases target the overall emissions reduction targets that governments adopt, and the regulatory framework to support them (or lack thereof). The advisory opinion is highly relevant to government framework cases because (1) most such cases challenge emissions reduction targets that are based on or reflected in governments’ Nationally Determined Contributions (NDCs) under the Paris Agreement and (2) plaintiffs often rely, directly or indirectly, on governments’ obligations under the climate change and international human rights law treaties, which form the basis of the advisory opinion.

Over the last 10 years, there have been a number of groundbreaking decisions in government framework litigation, including Urgenda Foundation v. State of the Netherlands (the Netherlands), Neubauer, et al. v. Germany (Germany), VZW Klimaatzaak v. Kingdom of Belgium & Others (Belgium), KlimaSeniorinnen v Switzerland (European Court of Human Rights (ECtHR)), and Do-Hyun Kim et al. v. South Korea (South Korea), where national and regional courts have found governments’ insufficient climate policies in breach of their legal obligations. The ICJ’s opinion not only builds on these precedents, it also provides greater clarity on some of the most contentious aspects of framework cases, in particular the standards against which a State’s compliance with its climate obligations must be assessed. This blog offers initial reflections on how the ICJ’s conclusions could shape the next generation of government framework litigation.  

A Definitive Conclusion On The Paris Agreement Temperature Limit

First, and at a fundamental level, the ICJ “consider[ed] the 1.5°C threshold to be the parties’ agreed primary temperature goal for limiting the global average temperature increase under the Paris Agreement” (para. 224). Drawing on the best available science, as well as political agreement in Conference of the Parties (COP) decisions, the ICJ thus resolved the debate on whether 1.5°C or “well below 2 degrees” of warming is the appropriate long-term temperature limit which should inform countries’ mitigation efforts. 

This conclusion reflects the findings of national and regional courts adjudicating recent government framework cases, including Klimaatzaak, KlimaSeniorinnen, Do-Hyun Kim, and Mathur, et al. v. His Majesty the King in Right of Ontario (Canada), which have relied on the 1.5°C limit to assess the lawfulness of governments’ climate actions. Even so, questions as to whether that was the right approach have lingered, as evidenced by the fact that several States, such as China, Côte d’Ivoire, and Russia, argued in the oral hearings for this advisory opinion that the Paris Agreement temperature limit was a range between 1.5° and 2°C. With the ICJ’s pronouncement, there is no debate that governments’ emissions reduction plans must be in line with the collective effort to limit global temperature rise to 1.5°C to prevent the most severe climate harms. 

Standards For Governments’ Mitigation Obligations

The ICJ’s findings regarding the “content” and “standards” of the obligations to mitigate climate change under the United Nations Framework Convention on Climate Change (UNFCCC) and the Paris Agreement also have significant implications for framework cases, and are likely to assist national and regional courts in adjudicating future cases, especially those focusing on the Ambition Gap. 

A central point that many governments put forward in framework cases, which high-emitting States also argued in the ICJ proceedings, is that the UNFCCC and Paris Agreement do not impose enforceable mitigation obligations. According to these States, the climate treaties are “entirely discretionary” (para. 249), “not onerous” and altogether non-binding (para. 175). The ICJ firmly rejected these arguments. On a fundamental level, it found that there are substantive mitigation obligations imposed by the UNFCCC and Paris Agreement, and identified a number of standards to that effect. 

In rejecting these arguments, the ICJ held that mitigation obligations under Article 4 of the UNFCCC cannot “be met merely by the adoption of any policies and the taking of corresponding measures” (para. 208). Similarly, the ICJ held that preparing, communicating, and maintaining successive NDCs is not enough to comply with obligations under the Paris Agreement. Rather, the “content of the NDCs is equally relevant to determine compliance” (para. 236). It is therefore clear that States’ mitigation obligations are substantive, not merely procedural. With regard to NDCs, States have “limited” discretion (para. 245). The ICJ outlined that, although the content of each State’s NDC will vary, it must represent: (i) a progression over its previous one (para. 241); (ii) reflect its “highest possible ambition” (para. 242); (iii) be informed by global stocktake outcomes (para. 243); (iv) be sufficiently transparent (para. 244); and (v) crucially, must “be capable of making an adequate contribution to the achievement of the temperature goal” (para. 242, emphasis added). 

Regarding the “adequate contribution” NDCs must make to the achievement of the temperature goal, the ICJ explained that States must collectively ensure that, “when taken together, [NDCs] are capable of achieving the temperature goal of limiting global warming to 1.5°C above pre-industrial levels” (para. 245, emphasis added).  

The practical application of these findings is significant. The ICJ found that States must determine their “adequate contribution” to the global effort based on the principle of common but differentiated responsibilities and respective capabilities (CBDR-RC). The ICJ cited the “key role” (para. 226) of this principle and found that States must prepare their NDCs taking into account “historical contributions to cumulative GHG emissions, and the level of development and national circumstances of the party in question” (para. 247), noting that developed country governments are to “tak[e] the lead” under Art 4(4) of the Paris Agreement. Significantly, the ICJ referred to the Paris Rulebook decision (adopted by Parties to the Paris Agreement), which, according to the ICJ, “requires each party to provide information together with its NDCs on how it considers the NDCs fair and ambitious in light of its national circumstances” (para. 248, emphasis added).

What are we likely to see as a result of this? States must now ensure that their NDCs, including those to be submitted for this year’s COP, (1) represent an adequate contribution to the global effort for 1.5°C, (2) collectively add up with other NDCs to achieve that aim, and (3) are fair and ambitious, in line with CBDR-RC – and thus historic responsibility. This leads to the conclusion that States must ensure their climate policies represent their fair share contribution to the collective climate mitigation effort to hold global temperature rise to 1.5oC. The importance of this conclusion lies in the fact that most States determine their reduction targets entirely divorced – instead of derived – from the required global effort. The inadequacy of this approach is central to most framework cases and is now authoritatively supported by the ICJ.

Finally, the ICJ emphasized that the standard of due diligence in this context is “stringent,” which means States must do their “utmost” to ensure they carry out their highest possible ambition (para. 246).

These strong findings by the ICJ build on national and regional courts’ findings over the past decade – such as those of the Dutch Supreme Court in Urgenda (para. 5.1.7, Urgenda) and the Belgian Court of Appeal in Klimaatzaak (para. 278, Klimaatzaak), which respectively required the Netherlands and Belgium to do “its part” to address the climate crisis. Most notably, what stands out is the symmetry of the advisory opinion with KlimaSeniorinnen – the 2024 ECtHR judgment that established human rights-based climate obligations, with application to 46 Council of Europe Member States, and formulated certain “standards” that States’ mitigation policies must meet (para. 550). Specifically, the ECtHR found that the “primary duty” for States is to “adopt, and to effectively apply in practice, regulations and measures capable of mitigating the existing and potentially irreversible, future effects of climate change” (para. 545, emphasis added). For measures to be “capable,” the ECtHR considered it crucial that they be based on the quantification of a national carbon budget, which must, in turn, be based on CBDR-RC (see here). The ECtHR further held that States’ margin of appreciation in setting the ambition of their emissions reduction efforts is “reduced” (para. 543), mirroring the stringent due diligence standard formulated by the ICJ. 

The ICJ’s conclusions on NDCs are particularly timely. With the third round of NDCs due in September, States will ideally adopt stronger targets to urgently close the Emissions Gap and comply with their legal obligations. If they fail to do so, individuals, organizations, and communities around the world are likely to draw upon the advisory opinion to attempt to hold governments accountable for insufficient climate action. At the time of writing, nearly 170 States have yet to submit an NDC. As it is now clear that States must develop an NDC that represents their share of the global mitigation effort for 1.5oC, and is fair and ambitious, in line with CBDR-RC, the coming months represent both a test and an opportunity for States to demonstrate their commitment to addressing climate change, as well as their alignment with the standards set out in this advisory opinion. 

Rejecting the “Drop In The Ocean” Argument

The ICJ also resoundingly refuted one of the most common defenses raised in government framework cases: that a State’s greenhouse gas emissions, when compared to the cumulative emissions of all other States, are too small to have a measurable impact on climate change. From Urgenda to Neubauer to Massachusetts v. EPA (United States of America), courts have repeatedly denied this “drop in the ocean” argument, yet governments continue to invoke it as a defense. Notably, and while not central to the holding of the case, the judge in Pabai Pabai and Guy Paul Kabai v. Commonwealth of Australia recently cited it as a reason why Australia does not owe a duty of care to Torres Strait Islanders affected by climate change (paras. 946-49). The ICJ, however, explained that (1) “while climate change is caused by cumulative [greenhouse gas] emissions, it is scientifically possible to determine each State’s total contribution to global emissions, taking into account both historical and current emissions” (para. 429) and (2) “the rules on State responsibility are capable of addressing situations where damage is caused by multiple States engaging in wrongful conduct, and that the responsibility of a single State for damage may be invoked without invoking the responsibility of all States that may be responsible” (para. 430). This effectively dismisses one of the main arguments advanced by governments and will undoubtedly strengthen the ability of plaintiffs to hold them accountable for climate inaction. 

Reaffirming the Role of Human Rights in Climate Litigation

Individuals, organizations, and communities bringing government framework cases often rely upon human rights law as a legal basis for challenging inadequate climate policies. The ICJ advisory opinion affirmed that governments’ obligations under international human rights law apply to the adverse effects of climate change (para. 372-386), referencing expressly climate litigation in national and regional courts (para. 385). Rights-based cases are thus strengthened, both on the merits and potentially to obtain access to court and remedies. In light of the ICJ’s finding that States must take their international climate change obligations into account when implementing their human rights obligations (para. 404), the ICJ’s opinion adds significant weight to findings by other courts that a failure to contribute a fair share mitigation effort constitutes a human rights violation (e.g., Urgenda, KlimaSeniorinnen) – and paves the way for other courts to reach similar conclusions in the future.

The ICJ’s conclusion that the right to a healthy environment is “essential for the enjoyment of other human rights” reaffirms the findings of national courts in framework cases of the last 10 years (para. 393). Plaintiffs in cases such as Leghari v. Federation of Pakistan, Shrestha v. Office of the Prime Minister et al. (Nepal), Future Generations v. Ministry of the Environment and Others (Colombia), Held v. Montana (United States), Do-Hyun Kim, and the Hungarian Climate Case have successfully leveraged the domestic right to a healthy environment – which is enshrined in the laws and constitutions of over 100 countries (para. 391) – to hold governments accountable for stronger climate action in a range of jurisdictions. The ICJ’s willingness to interpret the right to a healthy environment as a binding norm of international law will likely bolster national and regional framework cases that rely on this right, including pending cases such as Álvarez et al v. Peru and Indonesian Youths and others v. Indonesia.   

Advancing Intergenerational Equity

The advisory opinion’s conclusion that the sufficiency of a State’s climate commitments must be considered through an intergenerational equity lens marks a significant advancement in the normative power of this international legal principle. Over the last 10 years, a number of court decisions requiring governments to take stronger climate action have relied on intergenerational equity considerations to help determine that governments had violated their respective legal obligations, including the Urgenda District Court decision, Shrestha, Future Generations, Neubauer, KlimaSeniorinnen, Do-Hyun Kim, and the Hungarian Climate Case. The ICJ’s conclusion that “[d]ue regard for the interests of future generations and the long-term implications of conduct are equitable considerations that need to be taken into account where States contemplate, decide on and implement policies and measures in fulfilment of their obligations under the relevant treaties and customary international law” builds upon the legal reasoning in these successful cases (para. 157). Given the disproportionate impacts of climate change on younger generations, as well as the prevalence of framework cases featuring youth plaintiffs, the ICJ’s findings on intergenerational equity are poised to exert a profound influence on future and pending framework cases with youth plaintiffs in countries such as Canada, Indonesia, Sweden, Taiwan, and Turkey.  

Expanding the Potential for Broader Climate Remedies

What remedies courts should order in framework cases has been a key question in climate litigation. Courts to date have awarded a range of remedies, including orders concerning specific emissions reductions (e.g., Urgenda, Klimaatzaak (Court of Appeal)); the adoption of economy-wide legislative or regulatory frameworks (e.g., Shrestha, Future Generations, KlimaSeniorinnen,); and implementation of existing commitments (e.g., Friends of the Irish Environment v. Ireland, Commune de Grande-Synthe v. France, and DUH and BUND (Germany)). In some instances, courts have considered declaratory judgments recognizing a breach of obligations to be sufficient (e.g., Held).

The ICJ importantly found that a State breaching its climate obligations “may give rise to the entire panoply of legal consequences provided for under the law of State responsibility”, such as obligations of cessation, non-repetition, and performance, as well as full reparation, including restitution, compensation and/or satisfaction (para. 445). This finding offers a stronger legal foundation for national and regional courts to consider, for example, what restitution for emissions in excess of a carbon budget might entail, when compensation for climate harms should be awarded, and when to order more holistic and ambitious remedies.  

Conclusion: Toward Stronger Climate Accountability

The ICJ advisory opinion articulates very clearly States’ international obligations with respect to climate change. Its findings that States’ mitigation efforts must reflect their highest possible ambition, be capable of achieving the 1.5oC goal, and be fair and ambitious, determined through the application of CBDR-RC are momentous, as are its conclusions on remedies. Government framework litigation can serve to hold States to these obligations – just as plaintiffs have done for the past 10 years. Given the multitude of lawsuits pending against governments around the world – including in Austria, Belgium, Brazil, Canada, the Czech Republic, France, Indonesia, Italy, the Netherlands, New Zealand, Portugal, Spain, Sweden, Taiwan, Turkey and more – the ICJ’s conclusions could have global effects, as lawyers involved in these cases have observed. In addition, the ICJ’s findings will undoubtedly inspire and catalyze the emergence of new claims that will shape litigation in the decade to come unless governments take meaningful climate action now. 

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