On 23 July 2025 the International Court of Justice delivered its advisory opinion on the obligations of states in respect of climate change. The opinion responds to two questions put by the UN General Assembly in a resolution adopted in March 2023, after a campaign led by Vanuatu and supported by a large group of states. The judges reached their conclusions unanimously.
The first question asked what obligations states have under international law to protect the climate system for present and future generations. The second asked what legal consequences follow for states that, by their acts or omissions, have caused significant harm to the climate system.
The main findings
The Court found that states have obligations under the UN climate treaties, including the Paris Agreement, and under customary international law, including a duty to prevent significant harm to the environment and a duty to cooperate. It held that these obligations require states to act with due diligence, and that the standard of due diligence is stringent given the seriousness of the threat.
On the Paris Agreement, the Court found that the 1.5°C goal has become the primary temperature goal agreed by the parties, and that nationally determined contributions must reflect each party's highest possible ambition. States do not have unlimited discretion in setting their NDCs, according to the opinion.
On consequences, the Court's summary states that a failure by a state to take appropriate action to protect the climate system from greenhouse gas emissions, including through fossil fuel production, fossil fuel consumption, the granting of fossil fuel exploration licences or the provision of fossil fuel subsidies, may constitute an internationally wrongful act attributable to that state.
The Court was careful about the scope of that finding, and the wording matters for how it may be used. The wrongful act is not emissions as such. It is the failure to meet due diligence obligations to prevent significant harm. Where a breach is established, the legal consequences can include cessation of the wrongful conduct, guarantees of non-repetition and full reparation, provided that a sufficiently direct and certain causal link can be shown between the wrongful act and the injury.
Advisory, not binding
Advisory opinions of the ICJ are not binding in the way that judgments in contentious cases between states are. They carry significant legal weight, however, because they represent the Court's interpretation of international law. National courts, regional human rights courts and other tribunals often refer to them.
The opinion follows two other international rulings on climate obligations. In May 2024 the International Tribunal for the Law of the Sea issued an advisory opinion finding that greenhouse gas emissions are marine pollution under the UN Convention on the Law of the Sea. The Inter-American Court of Human Rights issued its own advisory opinion on climate change and human rights in early July 2025.
Who is bound
The opinion addresses obligations of states, not companies. Its relevance to energy companies is indirect, through how states regulate the sector. The finding that licensing and subsidies may be relevant to a state's compliance with its obligations directly concerns government decisions on oil, gas and coal exploration and production, and on fuel price support.
The Court also found that obligations under customary international law apply to all states, including those that are not party to the climate treaties. That point attracted attention because the United States has announced its withdrawal from the Paris Agreement.
What it could mean for energy policy
The practical effect of the opinion will depend on how it is used. Several pathways are possible.
The first is domestic litigation. Climate cases against governments in national courts have increased over the past decade, and plaintiffs may cite the opinion in arguing that particular licensing decisions or subsidies are inconsistent with a state's international obligations. Courts in some jurisdictions give significant weight to international law in interpreting domestic obligations.
The second is diplomacy. Vulnerable states, including small island developing states, may cite the opinion in negotiations at COP30 in Belém and in discussions on loss and damage finance. The opinion's findings on reparation are likely to feature in those debates.
The third is regulatory decision-making. Governments considering new oil and gas licensing rounds, coal mine approvals or fuel subsidy programmes may face questions about how those decisions fit with the due diligence standard described by the Court. Some governments may choose to document climate assessments more thoroughly as part of approval processes.
Fossil fuel subsidies in context
The reference to fossil fuel subsidies is significant because subsidies remain widespread. Many governments, particularly in emerging markets, cap retail prices for fuels and electricity to protect consumers, and the cost of those caps rises when international prices increase. The International Monetary Fund and International Energy Agency have long tracked these subsidies.
The opinion does not say that all subsidies are unlawful. It says their provision may form part of a failure to take appropriate action, depending on the circumstances. For governments facing energy affordability pressures, the opinion adds a legal dimension to a policy area usually framed in fiscal and social terms.
Questions the opinion leaves open
The opinion leaves several questions for later. It does not set a formula for apportioning responsibility for historical emissions among states, and it notes the difficulty of establishing causation for specific harms. It does not specify which licensing decisions or subsidy programmes would breach the due diligence standard. Those questions would arise in contentious cases, which require the consent of the states involved, or in national courts applying domestic law.
The opinion also does not address the obligations of private companies directly. Some commentators have suggested it could support arguments that states must regulate corporate emissions more strictly, but that would depend on national legal systems and on how legislatures respond.
What to watch
The first test will be how courts and parties cite the opinion over the coming months, including in pending climate cases in Europe, Latin America and Asia. At COP30, the opinion is likely to shape negotiating positions on mitigation ambition, finance and loss and damage. For energy investors, the main question is whether it changes the legal risk attached to new fossil fuel licensing in particular jurisdictions.