The ICJ Advisory Opinion on Climate Change brings much needed renewed hope for climate justice
By Francesco Sindico - posted on 25 July 2025. This post is the second of two posts by Professor Sindico: the first is also available on the Strathclyde Law Blog.
This week’s release of the International Court of Justice Advisory Opinion has provided much needed clarity on the current status of International Law in relation to climate change state obligations. From my personal perspective, it was a very good Opinion and one that lays the foundations for a renewed hope in climate justice going forward. Why, you may ask. Whilst we all need more time to digest the Opinion properly, let me share with you a short normative chain that I believe can have a very strong impact.
- The Court confirmed that a) we are facing an existential threat to the planet – we are living a time of climate collapse and b) that the legal goal of the international community is 1.5 degrees centigrade, not 2.0.
- The level of due diligence required by States under international law to prevent significant harm to the climate system (which applies to all States) is based on the level of probability of risk of harm. This links science with law.
- Considering the science and the ongoing climate collapse, fossil fuel subsidies do not align with a state’s due diligence obligation to protect the climate system and may be unlawful under international law.
- This obligation (prevention of significant harm to the climate system) is an erga omnes obligation, which means that any State can raise its breach against a State in breach of such obligation on behalf of the international community.
A major political (and legal) implication of the ICJ Advisory Opinion outcome is that it now provides a normative shield vs populism and false economic arguments against renewables.
Like many others, I will take time to fully digest the Advisory Opinion released this week, but I look forward to working together with others in making the most of something we did not have until yesterday: clarity on what the law says when it comes to protecting the climate system, which, let us be clear, means protecting all of us and future generations!
Lastly, in a world where bad news is all over the place, let us celebrate this milestone. And let us thank the brave young students (now young adults) from Vanuatu who saw their dream become reality yesterday in The Hague. Let me also offer a huge thanks to Christina Voight and the International Union for Conservation of Nature for allowing me to co-lead an amazing group of Counsel to IUCN that contributed as the only international organisation not fully constituted by States to these historical proceedings.
You can see the Advisory Opinion online (together with a summary from the Court itself). IUCN World Commission on Environmental Law’s reaction to the release of the Advisory Opinion is available on its website.
Francesco is a Professor of International Environmental Law at Strathclyde Law School in Glasgow. He was Counsel for the International Union for the Conservation of Nature in the ICJ Advisory Opinion Proceedings. He coordinated a team of Counsel from all over the world led by the Chair of the IUCN World Commission on Environmental Law Prof Christina Voigt. Prof Sindico delivered part of IUCN’s oral statement before the ICJ in December 2024 together with Prof Voigt and IUCN Director