New International Court of Justice Advisory Opinion Raises Global Liability Stakes Around GHG Emissions and Climate Change amid U.S. Federal Regulatory Retreat

The Opinion interprets member states’ responsibilities under treaty and customary international law. In a sweeping and landmark declaration, the Opinion advises that member states have a duty to reduce emissions, regulate within their jurisdictions and may be legally responsible to provide restitution, compensation, or satisfaction for damages arising from breaches thereof. While non-binding, the Opinion is, in effect, a potent policy pronouncement likely to carry persuasive authority in pending and future climate-related legal and policy processes, both domestic and international. Further, its framing of state responsibility—including potential reparations and the attribution of private sector emissions to state actors—portends increasing legal pressure on governments and regulated industries, especially in jurisdictions with active youth, Indigenous, or rights-based climate litigation.

The ICJ
The ICJ, established in 1945 and based in The Hague, is the principal judicial organ of the UN. It adjudicates legal disputes between member states that have consented to its jurisdiction and provides non-binding advisory opinions on legal questions referred to by UN organs and specialized agencies. Its jurisdiction is therefore both compulsory and advisory.

Both the United States and Canada are parties to the ICJ by virtue of their membership in the UN, though each has limited its acceptance of the Court’s jurisdiction. Following the ICJ’s 1986 decision in Nicaragua v. United States, the United States withdrew its declaration accepting the Court’s compulsory jurisdiction and now participates in proceedings only with specific consent. In August 2023, Canada replaced its prior unconditional acceptance of compulsory jurisdiction with a declaration incorporating several reservations. Nevertheless, ICJ Advisory Opinions influence both international legal discourse and are often cited in shaping norms and policies domestically.

International Legal Obligations Addressed 
The Advisory Opinion is grounded in a sweeping library of international law, including:

• Treaties. Under instruments such as the UN Framework Convention on Climate Change (establishes a framework for international cooperation to combat climate change), the Kyoto Protocol (sets binding emissions reduction targets for signatory countries) and the Paris Agreement (commits parties to nationally determined greenhouse gas emission targets aimed to reduce the global temperature increase), states are expected to act with due diligence, as interpreted under the treaties and customary law applicable to climate change, cooperate in good faith and pursue emissions reductions consistent with limiting global temperature rise to 1.5°C above pre-industrial levels.
• Customary International Law. States have a general duty to prevent significant transboundary environmental harm and to cooperate in addressing global environmental risks.
• Human Rights and Environmental Agreements. The Court referenced obligations under other international instruments, including the Vienna Convention for the Protection of the Ozone Layer, the Convention on Biological Diversity and the UN Convention to Combat Desertification, among others, noting that environmental protection may intersect with the human rights obligations provided by these conventions.

The Opinion further distinguishes between erga omnes obligations (owed to the international community as a whole) and erga omnes partes obligations (owed among treaty parties), a distinction relevant to determining which states may invoke responsibility for non-compliance.

Legal Consequences for Breaches
The ICJ concluded that non-compliance with duties to reduce emissions and regulate domestically may constitute an internationally wrongful act. Legal consequences may include, among others:

• Cessation and Non-Repetition. States may be required to cease ongoing breaches and provide guarantees of non-repetition.
• Reparations. States affected by such breaches may seek restitution, compensation or satisfaction, subject to the existence of a sufficiently direct causal link between state conduct (act or omission) and climate-change-related harm.
• Responsibility for Non-State Actors. The Court clarified that states may bear responsibility for failing to exercise due diligence in regulating emissions by private entities.

On the complicated topics of attribution and causation science, the Advisory Opinion acknowledged the complexities presented by attribution and causation in the climate change context but concluded that the customary international law standards of ‘a sufficiently direct and certain causal nexus’ remain applicable. The Court affirmed that causation must be assessed in specific cases, but that cumulative and diffuse emissions do not preclude legal responsibility so long as a state’s acts or omissions materially contribute to the harm. It advised that factual and legal causation can be established even where multiple actors are involved, and that acts or omissions, not regulating private entities, can be attributable to a state.

Relation to Broader Legal Landscape
Placing the ICJ’s opinion in a broader legal context, this Advisory Opinion follows a series of recent pronouncements by other international judicial bodies. The Inter-American Court of Human Rights (IACtHR) recently issued an advisory opinion identifying climate change as a matter of human rights and characterizing certain obligations as jus cogens—non-derogable principles of international law. Similarly, the International Tribunal for the Law of the Sea (ITLOS) determined that greenhouse gas emissions fall within the scope of marine pollution, asserting states’ obligations to prevent harm arising from such emissions.

Collectively, these decisions inform the rapidly evolving development of international environmental law and liability landscape and will likely shape how UN member states interpret their legal responsibilities. The ICJ’s Opinion has been hailed by environmental organizations as a historic affirmation of international law’s role in advancing climate change-related regulation and compensation policy prerogatives.

Jurisdiction-Specific Implications

United States: Regulatory Developments 
The ICJ’s opinion comes amid a contrary regulatory trajectory in the United States. On July 29, 2025, the U.S. EPA announced its proposal to revoke its 2009 Endangerment Finding, which concluded that GHGs, specifically, CO2, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, endanger the public health and welfare. EPA’s proposal is subject to public comment through September 15, 2025, and is certain to be litigated. The Finding is the scientific and legal foundation undergirding the United States’ federal regulation of GHGs under the Clean Air Act, including vehicle emissions standards, power plant rules, and oil and gas methane regulations. If successfully adopted, the rescission of the Endangerment Finding essentially passes the baton to the U.S. Congress to legislate federal climate change policy if it is so inclined. An interim effect could be to reduce the preemptive power of federal law over individual states’ own climate regulation regimes.

EPA’s proposal to rescind the Endangerment Finding cites what Administrator Lee Zeldin described as procedural and statutory flaws in the 2009 Finding’s application of the Clean Air Act, rather than introducing fundamentally new scientific data. The proposal questions the legal interpretations underpinning the original Finding and is paired with a rollback of vehicle emissions rules. While referencing the Department of Energy’s 2025 Climate Working Group study, it primarily argues that the Obama administration misapplied regulatory authority, signaling an emphasis on statutory rather than scientific reassessment that the Agency says undermines the rationale for the 2009 Endangerment Finding, including findings from the Department of Energy’s 2025 Climate Working Group study, which was released concurrently for public comment. EPA Administrator Zeldin characterized the move as the most sweeping deregulatory action in U.S. history, and consistent with a quartet of major Supreme Court rulings over the last few years—Loper Bright Enterprises v. Raimondo, West Virginia v. EPA, Michigan v. EPA and Utility Air Regulatory Group v. EPA—that, collectively, have refined or retracted the remit of federal agencies to regulate in matters of policy.

Canada: Litigation and Infrastructure Considerations 
Turning to the United States’ northern neighbor, Canada, the contrast with the ICJ Advisory Opinion is less dramatic but no less significant. Unlike the United States, Canada is a party to both the Paris Agreement and the United Nations Framework Convention on Climate Change (UNFCCC). Thus, the Advisory Opinion may bear particular relevance as Canada considers large-scale energy infrastructure projects, potentially informing the legal and policy frameworks under which such projects are assessed and regulated.

The Opinion may bear on the trajectory of Canadian climate-related litigation. For example, in Mathur v. Ontario, plaintiffs have alleged that certain provincial emissions targets violate constitutional rights under the Canadian Charter of Rights and Freedoms. In that context, advocates may leverage the ICJ’s articulation of legal obligations as persuasive guidance for courts and policymakers in assessing the adequacy of such measures. Future interpretation of federal legislation—such as the Net-Zero Emissions Accountability Act—may also be further influenced by the principles affirmed in the Opinion, particularly the concept that states must act with due diligence to avoid harm to the climate system, taking a precautionary approach, as well as reinforcing notions of cooperation and transparency both domestically and with other nations around scientific and technical knowledge and adaptation and mitigation.

What’s Next?
The ICJ’s Advisory Opinion is likely to influence ongoing legal, regulatory and policy developments related to climate change both internationally and domestically within UN member states. At the international level, the Opinion could inform future climate negotiations, treaty interpretation, strategic cross-border litigation and the evolution of climate regulation and compensation regimes.

Domestically, jurisdictions may consider the Opinion when assessing the adequacy of climate change-related measures, particularly in litigation or regulatory contexts involving questions of precautionary due diligence, transboundary harm and cooperation. In the United States, it is notable that the Advisory Opinion comes alongside an opposite-direction regulatory shift by the U.S. EPA to rescind its foundational finding that GHG emissions endanger public health and the environment. In Canada, the Opinion may influence ongoing legal challenges and regulatory deliberations as persuasive international authority affirming Canada’s obligations under both treaty law (Paris Agreement, UNFCCC) and customary international law. Given Canada’s 2023 decision to introduce reservations to its acceptance of ICJ jurisdiction, the Opinion may also intensify scrutiny of Canada’s infrastructure decisions under its Net-Zero Emissions Accountability Act. Courts may be more inclined to evaluate provincial and federal climate policies through a rights-based lens, particularly where Charter challenges are involved. The resulting public engagement and potential legal challenges may serve as a forum for evaluating the intersection of domestic law and evolving interpretations of international climate obligations.

For industrial actors, these developments signal dynamic and contrasting legal baselines: The ICJ Opinion could influence domestic permitting decisions and litigation strategies through its far-reaching articulation of member states’ obligations under customary and treaty law. Meanwhile, U.S. EPA’s reversal of the Endangerment Finding injects new regulatory uncertainty into a patchwork of U.S. federal and state climate regulations and litigation. Together, these moves suggest growing complexity in climate-related risk management, including for energy infrastructure, climate and sustainability disclosure practices and long-term capital investment strategy.