How small island nations are shaping global climate law at the ICJ

On 29 March 2023, the United Nations General Assembly took a historic step by requesting the International Court of Justice (ICJ) to provide an advisory opinion on states’ obligations under international law concerning climate change. This initiative, led by Small Island Developing States (SIDS) and spearheaded by Vanuatu, underscores the urgent need to address the existential threats climate change poses to vulnerable nations.

I was honoured to be part of this significant process, contributing as a member of the legal team representing the Republic of the Marshall Islands (RMI). Alongside my former PhD student, Dr Agnes Rydberg, we prepared the legal pleadings to help the Marshall Islands make their case before the ICJ. The experience was both intellectually challenging and deeply moving. It was deeply rewarding to receive a message of appreciation from Deputy Attorney General Johnathen Kawakami, who thanked me for contributing my expertise to the Marshall Islands’ case. His words underscored the strong sense of collaboration and shared commitment in this historic effort.

The ICJ proceedings have seen unprecedented engagement, with 91 written statements and 62 written comments submitted by states, international organisations, and civil society groups. Ninety-eight states and twelve international organizations will participate in the public hearings. Oral hearings took place from 2 to 13 December 2024.

The ICJ has been asked to consider two critical questions:

1. What obligations do states have under international law to protect the climate system from anthropogenic greenhouse gas (GHG) emissions for present and future generations?
2. What are the legal consequences for states that fail to meet these obligations and cause significant harm to the environment?

While ICJ advisory opinions are not legally binding, they carry significant weight, helping to clarify and solidify international legal norms.

The Case of the Marshall Islands

The Republic of the Marshall Islands, a nation comprising 29 coral atolls and five islands, faces an alarming reality. With an average elevation of less than 2 metres above sea level, rising sea levels and a legacy of nuclear contamination threaten the very existence of the Marshallese people.

On 5 December 2024, I was in The Hague as part of the Marshall Islands’ legal team for the ICJ hearings. The delegation included:

• Ambassador John Silk (Ambassador to the United Nations)
• Kathy Jetnil-Kijiner (Climate Envoy)
• Johnathen Kawakami (Deputy Attorney General)

Listening to Ambassador Silk’s statement brought home the gravity of the situation. He said:

“The Marshall Islands faces uniquely complex challenges because of our colonial and nuclear legacy. The burden left by nuclear testing is now compounded by rising seas. Our people live with mounting anxiety as the dome containing nuclear waste – a remnant of a painful past – faces submersion with the rising seas, threatening further nuclear contamination. Communities displaced because of nuclear testing are now at risk of being displaced a second time because of climate change.”

Legal Arguments on State Responsibility

Our legal arguments centred on state responsibility and the customary international law principle of prevention. This principle holds that states have a duty to prevent harm once the risk is known. Deputy Attorney General Johnathen Kawakami eloquently articulated this point:

“States have known that emissions would cause significant harm to the climate system since at least the 1960s – long before the adoption of the United Nations Framework Convention on Climate Change (UNFCCC) and the Paris Agreement. These treaties do not displace or exclude states’ customary law obligations under the prevention principle or other treaty obligations related to climate change.”

Our submissions also highlighted the importance of human rights and the principle of intergenerational equity—the duty to protect future generations from the consequences of climate change. Working with the Marshall Islands to bring these arguments forward was a reminder that climate justice is not abstract; it is a matter of survival for many communities.

Global Context and Related Cases

This ICJ advisory opinion is part of a broader movement in international law to address climate change. Recent developments include:

1. International Tribunal for the Law of the Sea (ITLOS)
   On 21 May 2024, ITLOS issued an advisory opinion affirming that GHG emissions absorbed by oceans constitute marine pollution. States must take “all necessary measures” to reduce emissions based on scientific evidence and international legal obligations.
2. Inter-American Court of Human Rights
   The court is currently considering a request for an advisory opinion on climate emergency and human rights, submitted by Colombia and Chile.
3. European Court of Human Rights (ECtHR)
   On 9 April 2024, the ECtHR ruled on several climate cases, including Klimaseniorinnen v Switzerland, where the court found Switzerland had failed to meet its obligations under Article 8 of the European Convention on Human Rights by not implementing adequate GHG reduction measures.

These cases reflect a growing consensus on states’ legal duties to combat climate change and protect vulnerable populations.

The ICJ’s opinion has the potential to clarify states’ legal responsibilities and offer a path toward justice for nations facing the worst impacts of climate change. While the opinion may not be legally binding, its influence on future legal standards and international policy could be profound.