ICJ Rules States Must Act On Climate Change Obligations

In a significant development for global climate justice, the International Court of Justice (ICJ), the main judicial body of the United Nations, has issued its long-awaited Advisory Opinion on the legal responsibilities of states regarding climate change. The court has clarified that countries around the world are required under international law to reduce greenhouse gas (GHG) emissions and take action to adapt to climate change. While the opinion is non-binding, it carries significant weight and could spur future legal actions, especially from developing nations vulnerable to climate change seeking reparations for the damages caused.

The opinion follows a formal request from the United Nations General Assembly (UNGA) for the court’s guidance in 2023. This request aimed to clarify the responsibilities of states in protecting the environment from climate-related harm stemming from GHG emissions. It also sought to clarify the legal consequences of actions—or inactions—that seriously harm the climate, particularly affecting small island developing nations and future generations. This historic request was led by the Pacific Island nation of Vanuatu, which first proposed seeking such an opinion in 2021. The ICJ’s conclusion is the most authoritative interpretation so far of how existing international laws relate to the climate crisis.

In its advisory opinion, the ICJ stated that all countries that are parties to the United Nations Framework Convention on Climate Change (UNFCCC)—ratified by all UN member states—must take effective steps to reduce GHG emissions and facilitate adaptation to climate change. This includes incorporating climate actions into national policies and ensuring that responses reflect scientific knowledge and international climate goals.

The court also stressed the unique responsibilities of developed nations. Wealthier countries have a greater obligation under international law to lead global efforts against climate change. This includes not only reducing their own emissions but also boosting carbon sinks and reservoirs. The principle of “common but differentiated responsibilities,” which has long informed international climate negotiations, was implicitly reaffirmed, providing additional legal support to the ongoing demands of developing nations.

The ICJ further interpreted the Paris Agreement—signed by nearly all countries—as requiring state parties to develop and maintain Nationally Determined Contributions (NDCs) that support the goal of limiting global warming to 1.5°C above pre-industrial levels. Although the opinion did not create new legal rules, it clarified that existing commitments under international treaties like the UNFCCC and Paris Agreement have enforceable legal weight and must be fulfilled in good faith. The U.S., which began the process of withdrawing from the Paris Agreement under the Trump administration, was indirectly mentioned, highlighting the importance of ongoing participation and compliance.

Importantly, the opinion also emphasizes the legal need for international cooperation. Countries must collaborate to meet the objectives of the UNFCCC and the Paris Agreement. This includes responsibilities related to the transfer of climate finance and green technologies, especially from developed to developing countries. Such cooperation should be carried out in good faith, reaffirming that solidarity is vital to addressing a crisis that crosses borders.

Legal analysts suggest that while the ICJ’s advisory opinion is not legally binding, its moral and legal authority could inspire new waves of climate litigation. Developing countries, especially those already facing rising sea levels, severe weather events, and loss of livelihoods, may now be better positioned to seek accountability and financial compensation from wealthier polluting nations. The opinion could also influence how local and regional courts interpret climate responsibilities, thus shaping legal precedents for years ahead.

Danilo Garrido, Legal Counsel at Greenpeace International, described the ruling as a significant advance. “The ICJ advisory opinion marks a turning point for climate justice. It has clarified the international climate obligations of states and, importantly, the consequences for failing to meet these obligations,” he said. “This will open the door for new cases and hopefully deliver justice to those who, despite contributing the least to climate change, are already suffering its worst effects.”

As global temperatures keep rising and climate impacts worsen, the ICJ’s opinion might play a crucial role in changing international climate governance. It serves as a legal guide for countries dealing with complex environmental obligations, setting the groundwork for more effective climate action and possibly reparations for those most affected by a crisis they did not create.