An analysis of the opinion and its implications by David Frydlinger, Cirio Law Firm

Cirio has prepared a comprehensive briefing outlining the recent advisory opinion from the International Court of Justice (ICJ) on State responsibility for climate change and what it means in practice.

Issued on 23 July 2025, this is the ICJ’s first advisory opinion addressing climate change. It marks a significant development: the Court has clarified that key climate-related duties, keeping global temperature rise below 1.5 °C, pursuing progressively ambitious climate action, and cooperating internationally while providing reparation, are not optional. These are binding legal obligations owed by States not only to each other, but also to people living today and to future generations.

This landmark opinion signals a shift in the role of climate diplomacy. What was once primarily a matter of international politics is now embedded within a framework of international law. The implications are broad and immediate: the opinion is expected to shape future Nationally Determined Contributions (NDCs), inform corporate transition plans, and is already influencing the EU’s ongoing Omnibus negotiations.

The Opinion transforms climate change from a realm of political aspiration into one of legal obligation. The Court holds that the 1.5 °C temperature ceiling, the duty of progressive ambition and the obligation to co-operate are binding norms owed erga omnes – to all States, to peoples and to future generations. That clarification re-sets the expectations that fall on governments, corporations and financial actors

David Frydlinger, Cirio

To help navigate the legal and practical consequences of the opinion, Cirio’s full briefing is available below.