By Sir Ronald Sanders

In December 2022, these states made a bold request for the first-ever advisory opinion on climate change from the International Tribunal for the Law of the Sea (Itlos). This request sought clarity on states’ obligations under the United Nations Convention on the Law of the Sea (Unclos) to protect oceans from the adverse effects of climate change caused by greenhouse gas (GHG) emissions.

In May 2024, Itlos delivered a historic, unanimous opinion confirming that GHG emissions constitute marine pollution, obligating states to take affirmative steps to protect the marine environment, based on scientific evidence to prevent catastrophic harm.

This opinion has opened the door for all states -not just small island developing states (SIDS)- to pursue climate justice. It is also likely to influence how international and national courts address climate change, as other developing states push back against the threats to their countries caused by emissions from industrialized nations.

Frustration with the inadequate outcomes of the annual Conference of the Parties (COP) of the United Nations Framework Convention on Climate Change (Unfccc), led small states to take legal action. The COP meetings have been long on promises, but short on meaningful deliverables.

In 2021, on the sidelines of COP26, Antigua and Barbuda, along with Tuvalu, took the initiative to establish the Commission on Small Island States and International Law (Cosis). Cosis was mandated to leverage international law to support SIDS in their fight for climate justice.

The organization has since been joined by several other small states, motivated by the failure of global climate negotiations and their disproportionate vulnerability to rising sea levels.

Sea level rise is one of the most urgent challenges these nations face. Global sea levels have already risen by more than 10 cm between 1993 and 2024, threatening not only the physical existence of islands like Tuvalu and the Maldives but also posing immediate challenges to food security and displacement.

Some projections indicate that by 2100, 5 percent or more of the land in small island states could be permanently submerged. With no international law obliging other states to accept climate refugees, these small island nations acted urgently to protect their populations from the looming prospect of displacement.

Through Cosis, nine small island states turned to international law for redress. Forty states and international organizations participated in the Itlos proceedings, and the 2024 opinion is expected to set a significant legal precedent.

While advisory opinions are not directly enforceable, they provide authoritative interpretations of international obligations. In practice, such rulings create legal precedents that influence how future cases are judged, both in international courts and domestic legal systems. The Itlos opinion not only shapes the understanding of climate obligations under Unclos but could also provide the foundation for future compensation claims from affected nations against major emitters.

This opinion has already found broader application in other key cases. In January 2023, Chile and Colombia requested an opinion from the Inter-American Court of Human Rights on state parties’ obligations under the American Convention on Human Rights, specifically regarding the impact of climate change on human rights such as the rights to life, the rights of children, future generations, and indigenous communities.

Four months later, in April 2023, Vanuatu spearheaded efforts that resulted in a UN General Assembly resolution requesting an advisory opinion from the International Court of Justice (ICJ). This request sought clarity on states’ obligations under international law, including the UN Charter, the Unfccc, and the Paris Agreement, regarding the legal consequences for states that have caused significant harm to the climate and environment, particularly for vulnerable states and future generations.

The Itlos opinion can also be used to pressure industrialized nations into more ambitious climate commitments by highlighting their legal duty to mitigate harm. States may face increasing litigation from vulnerable countries seeking reparations or stronger mitigation efforts based on this legal groundwork.

There is also potential for suing coal and oil and gas producing companies which are responsible for a large share of global greenhouse gas emissions and, consequently, to climate change. A recent report shows that 57 oil and gas companies are responsible for 80 percent of global carbon dioxide emissions. These companies have continued to expand fossil fuel production even after the signing of the Paris Agreement​. Hence the call by many small island states for a global levy on them to pay compensation for damage.

It is this potential for actionable legal consequences that makes the Itlos opinion more than symbolic -it establishes a critical link between legal principles and practical climate action, pushing global powers toward greater accountability.

International law acts as both a shield and a weapon for small states confronting existential threats. The success of the Itlos Opinion demonstrates the potential of legal action in securing climate justice. For this reason, small states should unite to fully leverage international law in addressing the profound impacts of climate change – rising seas, shifting borders, food insecurity, and the displacement of their populations.

By the time major greenhouse gas emitters act to save themselves, these islands may already be reduced to mere rocks, unable to claim nationhood or sustain their populations.