Climate change reaches world's highest court

In recent years, national courts have played an increasing role in the determination of climate change issues. At the same time, international courts and other international judicial institutions are also being asked to join the debate.  In April, the European Court of Human Rights issued its landmark decision in KlimaSeniorinnen v Switzerland, finding that Switzerland had breached its duties under the European Convention of Human Rights by failing to take sufficient action to mitigate the effects of climate change. 

In addition, advisory opinions have been sought from international courts seeking clarification on the extent of States’ climate obligations under international law. In May last year, the International Tribunal for the Law of the Sea issued an advisory opinion ruling that anthropogenic greenhouse gas (GHG) emissions are a type of marine pollution under the United Nations (UN) Convention on the Law of the Sea. In April and May, the Inter-American Court of Human Rights held hearings on States’ obligations to protect human rights from climate change. Its advisory opinion is expected this year. 

Most recently, in December, climate change reached the world’s highest court, the UN International Court of Justice (ICJ), which held hearings in advisory proceedings to determine the extent of States’ climate obligations under international law. It is the first time the ICJ has been asked to address these issues. The ICJ’s advisory opinion is also expected this year.

Whilst advisory opinions from international courts are not binding on States, the views of the ICJ and other international courts on these issues could add significant weight to the direction of climate governance and international and domestic climate change litigation in future.

The ICJ advisory proceedings 

The ICJ proceedings follow a March 2023 resolution by the UN General Assembly which voted to refer a request to the ICJ for an advisory opinion clarifying the obligations of States in relation to climate change under international law. The initiative was driven by a group largely comprised of small island developing States led by Vanuatu. The resolution was co-sponsored by 132 States.

The ICJ has been asked to consider:

• What are the obligations of States under international law to protect the climate system and the environment from GHG emissions for present and future generations?
• What are the legal consequences that arise for States that fail to meet these obligations and cause significant harm to the climate system and the environment?

In doing so, the ICJ will have to navigate a broad range of complex issues and highly polarised arguments. A central issue is the extent to which climate obligations on States are limited to the UN climate treaty regime (e.g. the UN Framework Convention on Climate Change, the Kyoto Protocol and the Paris Agreement) or whether other sources and general principles of international law, such as human rights laws and the principle of prevention of transboundary harm, are also relevant. Connected to this is the question of whether the largest emitting States are required under international law to compensate for damage caused by their historic emissions. 

Potential impact of the ICJ’s opinion once published

Until the ICJ’s advisory opinion is published, it is possible only to speculate as to its likely impact. That said, it is widely anticipated that the opinion will become part of the blueprint for international cooperation on addressing climate change and play a significant role in framing climate governance and accountability in future. In the words of UN Secretary-General António Guterres, the opinion will have a “long-standing impact on the international legal order”.

Whilst ICJ advisory opinions are not binding on States, they carry important persuasive weight in international law. The high levels of engagement from States, international organisations and other actors in the proceedings give a clear indication of the opinion’s likely significance. The proceedings have been described as the largest ever case before the UN court with over 100 States and international organisations participating in the hearings.

A strong opinion from the ICJ will provide an important authoritative statement of international law on the obligations of States in relation to climate change and could be a powerful tool for those seeking to hold both States and companies accountable for climate change. 

Although the ICJ’s opinion will be limited to States’ obligations under international law, the ICJ’s views and the interventions of other international courts in the climate debate mentioned above will have implications for the public sector and companies. For example, States may be influenced to revisit their existing domestic climate policies and regulatory frameworks to ensure they meet their international law obligations, which could lead to new opportunities and challenges for companies to navigate. 

Developments in international climate law could also invigorate claimants behind strategic climate litigation cases and influence the future trajectory of climate litigation cases against public bodies and companies, especially high emitters, as we have seen with the Paris Agreement.  

With thanks to Knowledge Paralegal, Anya Cook, for her assistance writing this post.