International Court of Justice sets the pace for climate action

Nicolas Lockhart is a partner at Sidley Austin in Geneva, and Dominic Coppens is a senior adviser at Sidley Austin in Brussels and a professor of international economic law at Maastricht University, where he is co-director of the Institute for Globalisation and International Regulation

The authors were part of the legal team representing Antigua and Barbuda in the ICJ proceedings 

The ICJ’s recent opinion was unanimous, bold and clear

At a glance

• On July 23, the International Court of Justice delivered a unanimous advisory opinion on the global obligations of states on climate change

• The court gave the Paris Agreement legal teeth

• The opinion will make a real world difference

Faced with the existential threats of climate change to their small island state, a small group of students in Vanuatu launched an initiative that took them to the highest global court, the International Court of Justice. 

On July 23, the ICJ delivered a unanimous advisory opinion on the international obligations of states on climate change. Unanimous opinions are hard to reach and a rarity for the court. When unanimity is achieved, the necessary compromise is often at the expense of boldness and clarity. Yet, in this case, unanimity is coupled with both.

Legally, the opinion is rich. 

The court gave the Paris Agreement legal teeth that many had not seen. It rejected the view that Paris parties have a free hand to set their climate ambition. Beyond Paris, the court wove together the different parts of international law: the climate and biodiversity treaties, the law of the sea, human rights, and customary law. 

The resulting tapestry applies to all states, whether or not they are party to the Paris Agreement.

The ICJ ruled that states must take “stringent” action to protect the climate system as a “shared resource” to limit global warming to 1.5C. The science shows that 1.5C is rapidly approaching, and that states must reduce emissions sharply and quickly to meet this target. 

The shadow of the law has been illuminated in ways that will prompt action

The court stressed that this action must be based on fairness built into the Paris Agreement — and specifically, the principle of “common but differentiated responsibilities and respective capabilities”. 

Some countries with higher emissions have contributed more to climate change, and these countries have typically amassed greater resources to tackle the problem. As a result, while all states must act, developed countries must do more, with large developing countries expected to go further than a small island developing state.

Strikingly, the court has opened the pathway for legal responsibility — states that have violated international law through past or future failures may have to provide compensation to other states for the costly impacts of climate change.

Real world change

So much for the law, but will the opinion make a difference at a time when climate ambition is facing headwinds? The answer is yes. 

States tend to shift their behaviour towards the court’s opinions — the moral suasion of the law. In this case, states now make decisions on climate change knowing they can face legal consequences for shortcomings. The shadow of the law has been illuminated in ways that will prompt action.   

At the national level, there is a growing trend towards climate-related regulation: disclosures, due diligence, transition plans, and emissions standards. The opinion increases pressure for such regulation. Indeed, the court highlighted the duty to regulate the private sector effectively, covering emissions from production and consumption.

As states decide on their climate ambition, setting nationally determined contributions under the Paris Agreement, they now know that they do not have an entirely free hand and face enhanced litigation threats. 

The opinion will also be felt in the annual climate COPs. By articulating a bold and clear vision of the law, the opinion strengthens the negotiating hand of many states, whether pushing for more climate ambition, enhanced resilience, or fairer burden sharing. A co-operative agreement in the COP is always preferable to litigation — how much better to reach an agreement on climate finance or loss and damage, than face litigation?

Increased litigation

The opinion will, though, very likely lead to increased litigation. The opinion is part of a trend to take climate change to the courts, with cases against governments and companies.

Some suits seek more climate ambition into the future, and others responsibility for past emissions. The opinion will feed these trends, addressing responsibilities for both temporal dimensions. The ICJ’s unequivocal factual findings on climate science will also be influential in other courts.

The court places fossil fuel subsidies in the spotlight as a potential violation of international law

Further international litigation is, in particular, on the cards. The court has clearly set out this option and, in the absence of negotiated progress, some will follow it. 

While the ICJ has answered some of the legal questions arising from climate change, it has not answered them all. Uncertainties remain with a litigated approach.

The court’s opinion will have broader ripple effects. In the World Trade Organization, it will be cited in discussions on climate-related trade policies. 

For unilateral trade policies, where one country restricts imports for climate reasons, the ICJ has highlighted the vital importance of genuine international co-operation, and has identified guiding principles for action. These include sustainable development, common but differentiated responsibilities and respective capabilities, equity, intergenerational equity, and the precautionary approach.    

Fossil fuel subsidies

The opinion places fossil fuel subsidies in the spotlight as a potential violation of international law. 

This will probably energise WTO efforts to develop rules on these subsidies. It could also encourage countries to join the Agreement on Climate Change, Trade and Sustainability — the first international agreement to regulate fossil fuel subsidies. 

The influence of the opinion will also be felt when countries convene in Geneva this week to negotiate a global plastics treaty, in debates on deep seabed mining, and at COP30, in Belém, in discussions on energy transition, land use and sustainable agriculture, and climate finance and justice.

An initiative that began with a small group of students in Vanuatu and reached the highest international court will now set the tone for climate action across the globe. This, too, is a message sent by this opinion to present and future generations.

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