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Friday, 25 July 2025
 

Jorge Viñuales, Cambridge professor and Fellow of the Lauterpacht Centre.

 

 

 

 

 


This article first appeared on the Cambridge University website on 24 July 2025

 

The 'world court' and climate change

A Cambridge professor and counsel team member for Vanuatu gives his initial views on the landmark ICJ Advisory Opinion.
 

Cambridge professor and Centre Fellow, Prof Jorge Viñuales, and counsel team member for Vanuatu gives his initial views on the landmark ICJ Advisory Opinion. 

The International Court of Justice (ICJ), the judicial arm of the United Nations – known as the ‘world court’ – has issued a historic Advisory Opinion on the legal obligations of States in respect of climate change.

The ICJ opinion came after a two-year proceeding unprecedented in scale, which followed a UN resolution on a 2023 motion from Vanuatu: a Pacific island nation facing existential threats from extreme weather and rising sea levels caused by global warming.

Prof Jorge Viñuales, from Cambridge’s Department of Land Economy, was one of the top legal experts brought in by Vanuatu to help draft the original request to the Court, and has remained a key member of the counsel team.

Here, Viñuales shares his initial views on this landmark legal opinion:  

The ICJ’s opinion is remarkable in its scope, with the potential to open a new front in climate litigation. The opinion’s conclusions are deployable in the domestic courts of many nations as well as in international litigation to seek accountability for past climate harm.
No less importantly, the opinion was rendered unanimously by all members of the Court, despite differences of view aired in individual explanations of vote.

The Court largely sided with the Global South and small island developing States. It concluded – based on responses to a question asked by a judge at the end of the hearing – that legal responsibility encompasses not just greenhouse gas emissions, but also conduct that leads to emissions, such as production of fossil fuels, as well as subsidies that lead to increased production and consumption.

A government might claim it’s reducing emissions, but, in the view of the ICJ, if it’s supporting fossil fuel extraction or providing subsidies those actions are now expressly subject to climate obligations.

The Court stated that such obligations include the regulation of non-State actors such as corporations as part of conduct attributable to individual States in assessing their due diligence on climate change mitigation.

While the opinion itself does not carry legal force, the legal principles clarified by the Court are binding as part of international law, and the ICJ opinion points overall in the direction of climate justice. These principles will likely be used in courts the world over.

Some of the major fossil fuel-producing and greenhouse gas-emitting States had strongly argued against any reference to obligations beyond the comfort zone of the UN Framework Convention on Climate Change and the Paris Agreement, noting that these instruments are a lex specialis: treaties that exclude the application of all the other obligations.  

But the ICJ rejected this use of the lex specialis argument, opining that a wide range of obligations of treaty and customary law apply, from the UN charter to the law of the sea, human rights or customary international law, far beyond just the UNFCCC and Paris Agreement.

Recognising that the conduct of States which are large fossil fuel producers and GHG emitters is not shielded by the broad language of the UNFCCC and the Paris Agreement is fundamental for climate litigation, international and domestic.

The Court further confirmed that climate justice claims are governed by the general international law of State responsibility. This may pave the way for a fundamental shift in the legal architecture of climate justice claims.

Under this law of responsibility, the Court pointed to legal solutions for the recurrent arguments used by nations with large emissions to escape liability for climate harm. As a general matter, the ICJ has now accepted the principle of responsibility for climate harm, in a manner analogous to domestic climate litigation.

The application of the law of State responsibility means that where restitution is not possible States have an obligation to compensate and, remarkably, the Court recognised that this compensation may be due for “loss and damage”. The ICJ has advised that each injured State can act against any State that has breached its obligations and caused injury through climate damage.

The ICJ also reasoned that, from a legal perspective, existing maritime spaces or Statehood would not necessarily be put at risk by sea level rise. This is a fundamental point for Pacific nations that fought for the Advisory Opinion, several of which have maritime boundaries threatened by changing coastlines.

Climate devastation is increasingly common for low-lying South Pacific island nations such as Vanuatu. Warming temperatures create conditions for ferocious tropical cyclones, which – combined with coastal erosion – threatens lives right across the archipelago. Housing for more than a quarter of the population are at risk of sinking into the ocean within decades.  

The recognition by the ICJ of a right to a clean, healthy and sustainable environment is another very significant step. Previous resolutions from the Human Rights Council and UN General Assembly were insufficient, and this had not been robustly recognised in international law until this important opinion from the ICJ.
The legal focus on holding warming to 1.5 degrees above pre-industrial levels is also of considerable importance. While it is familiar to many, and has been a bedrock of the science for years, treaties such as the Paris Agreement were drafted to focus on a larger temperature increase. The ICJ’s opinion moves the focus from 2 to 1.5 degrees as the core objective.

In addition, the ICJ opinion strengthens the obligations arising from the Paris Agreement, stressing their due diligence character and the obligation for each State to display its “highest possible ambition”.

This conclusion of the Court is a key one, as it signals that the Nationally Determined Contributions – each country's commitments to reduce emissions – are not simply at the discretion of individual States, but under a genuine obligation that may be breached if such contributions lack stringency or are not implemented in good faith.

During the 2015 negotiations in the lead up to the Paris Agreement there was immense push back against this view. Now, we have it in an opinion from the top court in the world.

Given the global nature of the problem, this opinion should be welcomed really by everyone, particularly by the students and youth groups that came up with the idea in the first place and put so much heart and dedication into making this happen.

Read more about the background of Prof Jorge Viñuales's work with the Vanuatu student legal team here: www.cam.ac.uk/stories/climate-ICJ