ICJ climate opinion: implications for investment treaties

In July 2025, the International Court of Justice (ICJ) delivered its advisory opinion on the ‘Obligations of states in respect of climate change’.

The opinion confirms that states have legally binding obligations to protect the climate system and other parts of the environment from greenhouse gas emissions caused by human activities (‘anthropogenic emissions’). As noted in a separate declaration added to the opinion, these obligations have implications for international treaties that protect foreign investment, including in fossil fuels.

In 2023, IIED was among the first to highlight the relevance of investment treaty issues to the advisory opinion process. This new briefing unpacks what the advisory opinion means for international investment law and argues that climate obligations require states to align investment treaties with climate goals.