ICJ releases Advisory Opinion on Obligations of States in Respect of Climate Change

On July 23, 2025, the International Court of Justice (the “ICJ”) released its Advisory Opinion on the Obligations of States in Respect of Climate Change, concluding a two-year process initiated by a 2023 United Nations General Assembly resolution. The landmark opinion on the legal obligations of States to address climate change marks a pivotal moment for international law and environmental protection. While not legally binding, the ICJ’s findings affirm that States owe a duty to each-other to attempt to reduce emissions under both international treaties and customary international law. The ruling could have implications in Canada, including in several ongoing constitutional challenges related to Canada’s efforts to address climate change.

The General Assembly’s resolution requested the Court’s opinion on two questions:

• What are the obligations of States under international law to ensure the protection of the climate system and other parts of the environment from anthropogenic emissions of greenhouse gases for States and for present and future generations?
• What are the legal consequences under these obligations for States where they, by their acts and omissions, have caused significant harm to the climate system and other parts of the environment, with respect to:
  • States, including, in particular, small island developing States, which due to their geographical circumstances and level of development, are injured or specially affected by or are particularly vulnerable to the adverse effects of climate change?
  • Peoples and individuals of the present and future generations affected by the adverse effects of climate change?

The ICJ concluded that States are subject to binding obligations to protect the climate system from anthropogenic greenhouse gas emissions. It held that these obligations arise under various international treaties to which Canada is a signatory — including the United Nations Framework Convention on Climate Change, the Kyoto Protocol, and the Paris Agreement — as well as under customary international law. The Court emphasized that a breach of these obligations constitutes an internationally wrongful act, triggering the responsibility of the offending State to cease the wrongful conduct, provide assurances of non-repetition, and make full reparation to injured States, including restitution, compensation, and satisfaction, provided that a sufficiently direct and certain causal nexus can be established.

As a party to the UNFCCC, the Kyoto Protocol, and the Paris Agreement, Canada has adopted greenhouse gas emissions reduction targets in an effort to meet its international commitments. Although the Advisory Opinion is not legally binding, it may be relied on as an authority against Canada brought by other States in international legal contexts. Domestically, it may also be cited by plaintiffs in allegations  that federal and provincial governments are failing, through action or inaction, to prevent serious environmental harm.

Notably, the Advisory Opinion is not directly concerned with the availability of remedies for individuals suffering the effects of climate change under international law, despite the Opinion making statements recognizing intergenerational impacts of environmental harm. In contrast, there are several cases advancing through Canadian courts in which the plaintiffs make allegations about the rights of youth, as individuals, to a healthy climate.

In La Rose v. Canada, the Federal Court of Appeal held that it was not plain and obvious that the plaintiffs’ claim that Canada’s inaction on climate change deprived them of security of the person under section 7 of the Charter of Rights and Freedoms was doomed to fail. The Court reversed the Federal Court’s ruling which had struck the entirety of the pleadings. This case is scheduled to be argued on the merits before the Federal Court in an eight-week trial commencing in October 2026.

Similarly, in Mathur v. Ontario, the Ontario Court of Appeal remitted back to the Ontario Superior Court for a new hearing the claim that Ontario’s cancellation of prior GHG emissions reduction legislation was a violation of their s. 7 and 15 Charter rights. The Court of Appeal in Mathur found that the lower court erred in holding that the claim was seeking to impose a positive right on the provincial government, and instead concerned whether Ontario, having voluntarily set emissions reduction targets, was going about meeting that goal in a way that is constitutionally compliant. The concept of positive obligations arose in the La Rose decision as well, where the Federal Court of Appeal would not rule out the possibility that s. 7 of the Charter could be held to impose positive rights on the federal government.

These cases trail a decision of the Australian Federal Court, which overturned a lower court’s finding that the Australian Commonwealth Minister for the Environment owed a duty of care at common law to avoid causing personal injury or death to all people in Australia under 18 years of age at the time of the commencement of the proceeding arising from the emissions of carbon dioxide from the combustion of coal. In that case, that court did not find that there was a duty of care in the sense argued by the plaintiffs in the Minister’s Authority under the relevant legislation. In July of this year, the Australian Federal Court again did not find that the Commonwealth owed a duty of care to individual Torres Strait Islanders with respect to the setting of greenhouse gas emissions reduction targets, or with respect to the funding of adaptation measures to mitigate the impacts of climate change.