How the Climate Change Advisory Opinion from the International Court of Justice is Influencing Domestic Jurisprudence
The International Court of Justice published its Advisory Opinion on Obligations of States in Respect of Climate Change exactly one year ago today. Unsurprisingly, it was immediately taken up by litigants in climate cases that have since been filed in countries around the world. More surprisingly perhaps, despite the relative ‘youthfulness’ of the Opinion and its formally non-binding status, it was also swiftly being cited in decisions by domestic courts, from countries with dedicated ‘duty of vigilance’ laws like France to ‘hands-off’ dualist jurisdictions like Canada. To mark the one-year anniversary of the ICJ AO, the authors of a pending research article present a summary of their conclusions on the far-reaching effects of the ICJ AO on domestic jurisprudence.
Contextualising the ICJ’s Landmark Advisory Opinion
First, it is important to establish the context of the ICJ AO as this partly explains the weight it is being afforded by domestic courts. The request originated from a 2019 grassroots campaign led by Pacific Island students in Vanuatu (the Pacific Islands Students Fighting Climate Change) who sought to clarify the legal obligations on States regarding climate change. Vanuatu’s government then brought the students’ initiative to the UN General Assembly where the request to the ICJ to issue an advisory opinion was adopted on 29 March 2023 and formally issued to the ICJ on 12 April 2023.
In due course, the ICJ received the highest level of participation ever in advisory proceedings before it, with 91 written statements in the initial phase, 62 written comments on the initial statements, and two weeks of public hearings in The Hague in December 2024 with 96 States and 11 international organisations providing oral statements. Following oral hearings, 65 States and international organisations then provided written replies to questions from the judges. In July 2025, the ICJ published its unanimous conclusions.
Subsequently, on 20 May 2026, the United Nations General Assembly adopted a resolution “stressing that climate change is an unprecedented challenge of civilizational proportions and that the well-being of present and future generations of humankind depends on our immediate and urgent response to it”, welcoming the ICJ AO and (inter alia) calling upon all States to comply with their respective obligations under international law to ensure the protection of the climate system and other parts of the environment from anthropogenic greenhouse gas emissions, as identified by the ICJ.
The ICJ AO also exists within a wider context of findings from other recent advisory opinions of international legal bodies – those from the International Tribunal of the Law of the Sea (ITLOS) and the Inter-American Court of Human Rights (IACtHR), with an advisory opinion from the African Court of Human and Peoples’ Rights still to come.
Although the ICJ AO has not created a new legal framework for addressing climate change, it has served as the dominant thread stitching together this global climate law tapestry. It has clarified, strengthened, and positioned existing obligations under international law – particularly the customary duties to prevent significant environmental harm and for states to cooperate in good faith. At the same time, it clearly articulated a stringent due diligence standard that is increasingly influencing climate litigation.
The ICJ AO performs another three functions that have enhanced its utility for domestic courts: first, it confirmed the longstanding practice of reliance on the IPCC reports, firmly establishing the factual baseline from which legal implications flow. Secondly, it structured and systematised public international law based on that factual foundation. Thirdly, the ICJ went some way to normalising the legal culture concerning the climate crisis. The potential consequences of the third function are profound: legal culture directly influences the exercise of legal interpretation, how claims are framed, and how they are determined. As Tigre notes:
“The opinion does more than clarify individual legal duties. It reframes the relationship between science and law, between national discretion and responsibility, and between climate policy and binding legal obligation”.
An overview of the domestic decisions
This wide-ranging influence can be seen from a selected trio of decisions of domestic courts citing the ICJ AO. The three cases are the interim decision in Lho’imggin et al. v Her Majesty the Queen, a case before Canada’s Federal Court (September 2025); Greenpeace Netherlands and 8 citizens of Bonaire v The Netherlands, decided by the District Court of the Hague (January 2026), and Notre Affaire a Tous v Totalenergies SE, decided by the 34th Chamber of the Paris Court of Justice (June 2026).
Taking these in turn, in Canada the Federal Court engaged substantively with the ICJ AO in its interim ruling in Lho’imggin, granting the applicants leave to amend their Further Statement of Claim. The Lho’imggin case was originally filed in February 2020 by Dini Ze’ (Head Chiefs) from the Wet’suwet’en Likht’samisyu clan against the Canadian government on both constitutional and Charter-related grounds. In the original statement of claim, the plaintiffs alleged that Canada had failed to enact legislation and policies to meet its international climate commitments and that its approval of high-emitting fossil fuel projects ran counter to achieving the country’s 2030 and 2050 emissions reduction targets. The plaintiffs sought two broad declarations: 1) that the Canadian government might withdraw its approval for the continued operation of the contested fossil fuel projects, if it was determined that Canada would not be able to keep its emissions on a Paris-aligned pathway; and 2) an order requiring the government to establish an independent accounting system to keep track of Canada’s cumulative greenhouse gas emissions.
As part of the case’s progression, a Further Amended Statement of Claim (the Further Amended Claim) was filed by the plaintiffs, introducing the “Temperature Commitment” relating to the Paris Agreement. The Federal Court, in its interim decision on whether to strike the plaintiffs’ Further Amended Claim, acknowledged that the Temperature Commitment is “reaffirmed” or partially incorporated in domestic Canadian law through the Greenhouse Gas Pollution Pricing Act and the Canadian Net-Zero Emission Accountability Act. This is significant because, as the Court noted, Canada’s legal system adopts a dualist approach to international law, meaning that the Canadian courts cannot directly enforce Canada’s international climate commitments under the Paris Agreement unless these commitments are specifically incorporated into domestic legislation.
Throughout the interim decision, the Federal Court makes multiple specific pronouncements on the relevance of the ICJ AO for the arguments being raised by the plaintiffs. In para. 44, the Court explicitly acknowledges the scope for its interpretative role in domestic Canadian courts, stating “While the ICJ Opinion is not binding in Canadian courts, these pronouncements may have significant legal implications in the Canadian context. The principles outlined in the Opinion can influence how courts interpret domestic laws, particularly in relation to constitutional rights and international obligations.”
Having already noted the arguments raised by the plaintiffs alleging a breach of customary international law, the court weaves in a direct point on the ICJ AO, remarking that the AO, “connects the climate change obligations of states to a customary duty to prevent significant harm to the environment, a customary duty to cooperate for protection of the environment, and to human rights recognised under customary international law”, citing paras. 132, 140 and 145 of the AO. The Court goes further, reasoning in para. 63 that:
“at a minimum, Canadian courts may consider the ICJ Opinion in this and other cases by interpreting the alignment of domestic law with international legal instruments and customary international legal principles…This is especially true in cases where environmental protection intersects with constitutional rights. International legal principles may legitimately be invoked in domestic litigation when claimants are affected by actions that contravene customary norms or international treaty obligations.”
Although the Court approved the motion to strike the Further Amended Claim, given the “excessively broad” nature of the pleadings, the plaintiffs were granted leave to amend the claim. While it is up to the plaintiffs to decide whether and how to further refine their arguments, the Federal Court signalled that common law tort suits based on a violation of customary international law may find purchase before the Canadian courts (para. 113).
Turning to the Dutch courts, the District Court of the Hague determined a case brought by Greenpeace Netherlands and a group of Dutch citizens from Bonaire, an island municipality of the Netherlands against the Dutch government over its failure to protect the residents of Bonaire from the impacts of harmful climate change. The plaintiffs argued that in failing to enact adequate climate mitigation and adaptation measures, the Dutch government acted unlawfully under the Dutch Civil Code, as the islanders face ongoing and increasingly severe risks from heat stress, sea level rise, and ecosystem degradation, amongst other climate related harms. The plaintiffs also invoked Articles 2, 8, and 14 of the European Convention on Human Rights (ECHR) and referred to the Netherlands’ international climate commitments under the Paris Agreement.
In January 2026 the District Court of the Hague held that the Netherlands had—and continues to—act unlawfully by pursuing a climate policy that does not “make an equitable contribution” to the measures required to limit global warming to the 1.5°C temperature target and by failing to take adequate measures to protect Bonaire islanders from the effects of climate change. The Court ruled that, in treating the inhabitants of Bonaire differently from the European Netherlands when putting in place adaptation measures, the Dutch State is in breach of the Bonaire islanders’ Article 8 and 14 rights under the ECHR, in addition to Article 1 of the Twelfth Protocol to the ECHR. The Court ordered the Dutch government to produce more stringent mitigation and adaptation measures, including a requirement for the government to ensure that the targets established in the United Arab Emirates Framework for Global Climate Resilience are incorporated into a national adaptation plan that covers Bonaire, and are achieved by 2030.
In providing an overview of the relevant law for its decision, the Dutch District Court referred directly to the ICJ AO’s findings on States’ obligations of conduct and result. More specifically, the Court cites the ICJ AO at paras. 175 and 208 as relevant to its interpretation of the rules guiding the Netherlands’ climate commitments: “[at para. 175]…The Court [the ICJ] recalls that obligations of conduct in international environmental law entail an obligation to act with due diligence, requiring State parties to ‘use all the means at [their] disposal’ with a view to fulfilling their international obligations”. The District Court further points to para. 208, where the ICJ highlighted that:
“… it cannot be said that an obligation of result, such as an obligation to ‘adopt national policies and take corresponding measures on the mitigation of climate change’, will be met merely by the adoption of any policies and the taking of corresponding measures. To comply with this obligation of result, the policies so adopted and the measures so taken must be such that they are able to achieve the required goal. In other words, the adoption of a policy, and the taking of related measures, as a mere formality is not sufficient to discharge the obligation of result.”
Although the outcome of Bonaire has so far provided another milestone for enhancing climate action in the Netherlands, its ultimate reach will depend on the outcome of the appeal against this first-instance decision.
Finally, there is the decision of the Paris Court of Justice in Notre Affaire à Tous et al. v. TotalEnergies SE. This case concerned the scope of the French corporate duty of vigilance obligations as set out in Act No. 2017-399 of 27 March 2017 (the 2017 Act), which introduced a duty of care requiring corporations to establish and effectively implement due diligence plans for parent companies and contracting entities that meet certain threshold conditions. Notably, the duty of vigilance forms the basis for the EU’s corporate due diligence regime under the Corporate Social Due Diligence Directive of 13 June 2024.
Total had argued that the law could only apply to risks that the company was in a position to prevent and over which it is likely to have control, which is not the case with the global and systemic risks caused by global warming. As a single company cannot combat global warming on its own, Total argued this meant the 2017 Duty of Care Act could not reasonably include this issue within its scope. It also relied on the argument that measures to tackle global warming must be implemented by public authorities in accordance with the Paris Agreement, which binds States and not private actors.
The Court rejected those arguments, relying heavily on the ICJ AO’s findings when interpreting the 2017 Act. The Court pointed out at paras. 97, 98 and 100 of its decision the ICJ confirmed that States had an obligation, under international human rights law, to respect and ensure the effective enjoyment of human rights by taking all necessary measures to protect the climate system and other aspects of the environment, and that climate change treaties impose binding obligations on State Parties aimed at ensuring the protection of the climate system and other aspects of the environment against anthropogenic greenhouse gas emissions. The Court also pointed out the ICJ confirmed that customary international law obligations include the duty to prevent any significant environmental damage by acting with due diligence, and to use all means at their disposal to prevent activities under their jurisdiction or control from causing significant damage to the climate and environmental system.
The Court thus held that the meaning of the word “environment” within the 2017 Act included climate change caused by the release of GHG emissions into the atmosphere (at para. 139, citing the ICJ AO amongst other decisions) “as this constitutes a serious, present and future threat to the enjoyment of human rights according to the consensus view of scientists and international courts, climate risks must be taken into account by companies in their due diligence plans, since their identification forms part of the prevention of serious human rights violations”. This meant “the GHG emissions resulting from the activities of TotalEnergies SE and its subsidiaries – which are undisputedly contributing to global warming – form part of the climate risks falling within the scope of the Act on the duty of care of parent companies and contracting entities.” (para. 150).
As to the second key question before the Paris Court of Justice, whether GHG emissions arising from the combustion of fossil fuels which were produced by Total and its subsidiaries were within the meaning of the law (i.e. whether Scope 3 emissions had to be included in addition to Scope 1 and 2 emissions), the Court noted Chapter VI on climate change of the OECD Guidelines for Multinational Enterprises on Responsible Business Conduct, the UK Supreme Court’s decision in Finch v Surrey County Council [2024] UKSC 20 (in addition to other relevant decisions), and held:
“182. It follows from the above that Scope 3 GHG emissions – for which a causal link to energy production has been established and over which TotalEnergies SE is able to exert influence – form part of the adverse impacts resulting from the group’s own activities.
183. The Scope 3 GHG emissions of TotalEnergies SE’s subsidiaries are therefore among the risks arising from their activities that the parent company must identify in its due diligence plan in accordance with the scope of the 2017 Act.”
The Court then ordered Total to update its vigilance plan within six months of the service of the decision by including Scope 3 greenhouse gas emissions in its risk mapping and related measures.
Conclusion: The wider impacts are yet to come
We can see from this sample of decisions that domestic courts are relying on the ICJ AO not only to frame petitioners’ arguments but also as an aid when interpreting domestic legislation and determining the scope of obligations on both States and private companies. In short, even in dualist jurisdictions where international law is not directly legally binding, we see domestic courts accepting the legal findings of the ICJ AO can bear significant – and even potentially determinative – legal weight. Commentators who described the ICJ AO as ground-breaking were therefore right, notwithstanding, in many ways, the ICJ’s conservative adherence to well-established principles such as the frequent references to findings of the International Law Commission, and the ICJ’s careful citation of established legal authority for all articulated legal principles. Wewerinke-Singh and Viñuales rightly observed the global legal baseline pertaining to all domestic jurisdictions has now shifted, and so 23 July 2025 marks a clear delineation between pre-ICJ AO climate litigation and post-ICJ AO climate litigation.
More broadly, the field of climate litigation is continuing to evolve at a rapid pace. Together, the cases analysed above and in the authors’ forthcoming paper illustrate an emerging ‘horizontal’ (AOs influencing each other and domestic claim inspiring other domestic claims) and ‘vertical’ (international law influencing domestic law, and vice versa) global framework of climate accountability, involving claims not only against States for failures to regulate but also against major emitting corporations, reflecting the ICJ’s AO clear statement that States are obliged to put in place adequate regulatory regimes to prevent climate harm. The outcome of this emerging legal framework for the protection of the climate will, however, depend on how effectively regulators enforce mandatory obligations and governments dismantle the legal structures that continue to enable and encourage fossil fuel exploitation.
This article was written jointly by Nina Pindham and Emily Bradeen of the Grantham Research Institute of Climate Change and the Environment as a summary of their ongoing research on the impact this Opinion has had on domestic jurisprudence.
