Developments in international law: implications for science and evidence in climate litigation

The Climate Litigation Network supports national organisations that are taking legal cases against their governments in respect of the adequacy and implementation of national climate policies and targets ('framework’ cases). Over the last 10 years, there have been a number of groundbreaking decisions in government framework cases, including in the Netherlands, Germany, Belgium, South Korea and at the European Court of Human Rights. In these cases, national and regional courts have found governments’ insufficient climate policies in breach of their legal obligations. In July 2025, the International Court of Justice (ICJ) released its advisory opinion (AO) on the ‘Obligations of States in respect of climate change’. It provides a clear interpretation of key international law instruments, such as the United Nations Framework Convention on Climate Change and the Paris Agreement, as well as human rights conventions and international customary law. The ICJ AO builds on precedents set in national cases, and provides greater clarity on some of the most contentious aspects of framework cases, in particular the standards against which a State’s compliance with its climate obligations must be assessed. This opinion will be highly influential for framework cases around the world. Specifically, the ICJ found that States must ensure that their Nationally Determined Contributions (1) represent an adequate contribution to the global effort for 1.5°C, (2) collectively add up with other NDCs to achieve that aim, and (3) are fair and ambitious, in line with the principle of common but differentiated responsibilities. This presentation will examine how the ICJ AO findings are relevant to scientific studies and evidence being submitted in framework cases.