World Court Rules on Nation Responsibilities Regarding Climate Change Crisis

International Court of Justice Issues Landmark Opinion on Climate Change Obligations

The International Court of Justice (ICJ) has issued an advisory opinion on the obligations of states in respect of climate change, providing a comprehensive guide on the legal responsibilities of nations to combat climate change and protect the environment. The opinion, delivered on 23 July 2025, is expected to have far-reaching implications for states, international organisations, and the global community as a whole.

The ICJ's decision was prompted by a request from the Republic of Vanuatu, which sought to clarify the legal obligations of states under international law to prevent climate change and address its harmful effects. The opinion concludes that states have obligations under international law to prevent significant harm to the environment, combat climate change, and protect human rights.

The ICJ considers that a customary duty of states to prevent significant harm to the climate system and other parts of the environment arises as a result of the general risk of significant harm to which states contribute through activities undertaken within their jurisdiction or control. This duty includes taking precautionary measures, undertaking risk assessments, and environmental impact assessments, all of which require a heightened degree of vigilance and prevention.

In the context of climate change, the ICJ acknowledges that determining causation involves two distinct elements: attributing a climatic event or trend to anthropogenic climate change, and attributing damage caused by climate change to a state or group of states. The ICJ's opinion is based upon its assessment of the relevant scientific background, primarily relying on the reports of the Intergovernmental Panel on Climate Change.

The ICJ views the right to a clean, healthy, and sustainable environment as a human right, concluding that the adverse effects of climate change may impair enjoyment of human rights such as the right to health and an adequate standard of living. The ICJ also emphasises the importance of states actively pursuing scientific and technological information, as well as knowledge-sharing initiatives, to assess the probability and seriousness of possible climate harms.

The ICJ's opinion builds upon a growing body of both national and international case law, such as the Netherlands judgment against a multinational energy group and the KlimaSeniorinnen ruling by the European Court of Human Rights. These cases have challenged states for failing to take adequate action on climate change and climate commitments. The trajectory of climate litigation is therefore likely to accelerate in light of the ICJ's opinion.

The opinion also highlights the need for developed countries to take the lead in combatting climate change. The ICJ concludes that the principal climate change treaties impose legally binding obligations on states to prevent climate harms, adopt mitigation and adaptation measures, and cooperate in good faith. However, fulfilling treaty obligations alone does not mean that states have also fulfilled their customary law obligations. Treaties and customary international law inform each other, but do not necessarily overlap.

The duty to cooperate for the protection of the environment forms part of customary international law, but does not excuse states from co-operating with the requisite level of due diligence. Due diligence should account for current standards contained in climate treaties and customary international law, and other sources such as decisions of the Conference of the Parties. The standard required in each case will be specific to each state's respective circumstances, with developed states expected to take more demanding measures to prevent environmental harm.

Under international law, the human right to a clean, healthy, and sustainable environment is essential for the enjoyment of other human rights, such as the right to health and an adequate standard of living. States must act with stringent due diligence to prevent harm to the environment, including implementing regulations for significant and sustained reductions of greenhouse gas emissions and robust enforcement and monitoring mechanisms. A failure to act may constitute an "internationally wrongful act" entailing responsibility under international law.

In conclusion, the ICJ's advisory opinion provides a significant step forward in clarifying the legal obligations of states to combat climate change and protect the environment. The opinion underscores the need for states to take immediate and decisive action to address climate change and its harmful effects, and to prioritise the protection of human rights in their efforts to create a sustainable future for all.