SIDS on the Frontline of Climate Justice

Author: Irem Cakmak, LLM

October 21, 2025

[Image source: Markus Spiske]

Introduction

Small Island Developing States (SIDS) are a group of low-lying island nations with distinct vulnerabilities that make them particularly susceptible to the impacts of climate change, despite their minimal contribution to global emissions. These countries include Pacific islands such as Tuvalu, Kiribati, the Maldives, as well as many island nations in the Caribbean. The effects of climate change, such as rising sea levels, extreme weather, and the degradation of natural resources, pose serious threats to both countries themselves and the individuals living within them. 

SIDS have sounded the alarm about the existential threat of climate change, yet their pleas have often been drowned out because the struggle of these states to combat climate change has been profoundly unequal to that of larger, developed nations, mirroring the historical power dynamics and inequalities stemming from colonialism, which have shaped international law itself. 

A major turning point in the struggle of SIDS came  about in 2019, when twenty-seven students from Fiji formed the youth group Pacific Island Students Fighting Climate Change (PISFCC). These students utilized the platform created via their organizing to stress climate-related issues on an international level; they maintained that climate-related issues can significantly undermine human rights. Despite its profound global relevance, an authoritative clarification on the scope of state obligations regarding climate change, especially under customary international law and human rights law were missing. PISFCC aimed to ‘seek climate justice’ at the International Court of Justice by requesting the court to respond to a legal question that will develop international law, integrate legal obligations around environmental treaties and basic human rights, and clarify state responsibility for climate harm.’ PISFCC’s push to obtain an advisory opinion from the International Court of Justice (ICJ, the Court) eventually won the backing of Vanuatu (another SIDS), and later, 105 other states. 

Ultimately, on 29 March 2023, the United Nations General Assembly (UNGA) adopted Resolution 77/276, which asked the ICJ to issue an advisory opinion on states’ responsibilities regarding climate change. The General Assembly request centered on two questions: which obligations does international law place on states to protect the climate system? And, which legal consequences follow when states, through action or inaction, cause serious harm to it?

The ICJ’s advisory opinion is an important step in the struggle of SIDS, as it provides a powerful new legal framework which aids invalidating SIDS’ arguments, as well as in empowering future climate litigation. Furthermore, it shifts the discourse from a purely political debate to one grounded in international law and state responsibility. This is significant for SIDS because the legal framing creates enforceable obligations and opens the door to accountability, adjudication and potentially reparations, which political debate alone cannot provide. 

The Legal Nature and Authority of ICJ Advisory Opinions

ICJ is the principal judicial organ of the UN; it settles legal disputes between states and provides advisory opinions on legal questions referred to it by authorized UN entities and specialized agencies.

An advisory opinion is a legal interpretation provided by the ICJ to clarify legal questions (ICJ Statute, Art. 65). Unlike judgements in contentious cases, advisory opinions are not legally binding on states (ICJ Statute, Art. 59). This description implies that states cannot be compelled to adhere to the opinion, nor can it serve as a basis for formal enforcement action by the UN Security Council.

Despite their non-binding nature, advisory opinions carry legal authority and influence. Even if they do not establish new legal rules, they should be followed because they clarify existing binding rules, which the state parties are obliged to follow. While not all states are parties to every international treaty, ICJ advisory opinions clarify obligations under customary international law, which are universally applicable. Therefore, the ICJ's advisory opinions can profoundly shape the interpretation and development of international law, serving as a powerful source of clarification and legitimation for legal principles. For example, the Court’s 1996 Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons clarified the relationship between international humanitarian law and environmental law, influencing subsequent legal discourse and state practice on the issue. Advisory opinions can also provide a strong foundation for future litigation in domestic, regional, and international developments. A notable example is the Court’s 1996 Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons, which clarified that environmental protection is a part of customary international law that applies even under armed conflict. The 1996 Advisory Opinion embedded environmental protection within customary international law, applicable in law. The findings in this advisory opinion were relied on future cases (Pulp Mills 2010, Costa Rica v. Nicaragua 2015), been integrated into military manuals (for example UK Ministry of Defence, The Manual of the Law of Armed Conflict 2004, paras. 6.12-6.13), and reflected in the ICRC’s 2020 Guidelines on the Protection of the Natural Environment in Armed Conflict.

International law contains various instruments on climate change, including the 1992 UNFCCC, the 1997 Kyoto Protocol, and the 2015 Paris Agreement.  However, there are ambiguities regarding how these agreements interact with broader international law, including the principles of state responsibility and human rights law. This lack of clarity has historically hindered SIDS’ efforts to seek justice. For instance, the ambiguity of states’ due diligence obligations in climate-related matters was used to dismiss or delay legal claims by SIDS in various international forums prior to this opinion. This particular advisory opinion is important because it provides an authoritative legal framework for addressing climate change, clarifying state obligations and providing a basis for future climate litigation and policy. 

Unequal Responsibility, Unequal Impact

Among the pressing issues faced by SIDS, ranging from sea level rise to loss of natural resources, the threat of statehood loss is particularly prominent. The Maldives, Tuvalu, and Kiribati have extremely low maximum altitudes, making them highly vulnerable to inundation and land loss. Under the Montevideo Convention on the Rights and Duties of States, one of the criteria that the existence of a state is traditionally tied is ‘defined territory.’ The Montevideo Convention is widely regarded as a part of customary international law, meaning that the states are bound by it, even if they are not a party to the Convention. However, rising seas threaten habitability, by destroying arable land, freshwater supplies and infrastructure, rendering territory effectively unlivable. According to the IPCC, sea levels rise under high-emission scenarios, enough to submerge significant portions of SIDS’ land and render them uninhabitable by 2100. This raises unprecedented questions about whether physical disappearance means the end of statehood. Although a clear minimum standard for the territory criterion has not been established, the physical disappearance of these territories could undermine their recognition as states under international law, placing both their sovereignty and their people’s rights in jeopardy. If statehood is lost citizens risk statelessness, invalid passports, lack of consular protection and the collapse of currency systems, leaving them in a legal limbo.

Climate change prevents residents of these states from fully enjoying their basic human rights. In the case of Ioane Teitiota, a citizen of Kiribati sought asylum in New Zealand on the basis of being a climate refugee. He claimed the effects of climate change, such as water contamination and crop destruction, violated his right to life under the International Covenant on Civil and Political Rights. The United Nations Human Rights Committee, while not granting his claim, found that the effects of climate change could potentially violate a person’s right to life if they were returned to a country facing an imminent threat to life as a result of a changing environment. 

Greater historical responsibility lies with high-emitting states than with SIDS, particularly certain states in the Global North such as the United States, China and Germany. These states, which are often highly-developed and produce large quantities of greenhouse gases that facilitate rising sea levels and other climate consequences, have sizable land mass that does not subject them to the possibility of becoming uninhabitable due to rising sea levels. A high-emitting state is one that generates a significant amount of greenhouse gas emissions, often through industrial activity. The United Nations has repeatedly called on these states to take more decisive actions on climate change. For example, the UNEP Emissions Gap Report (2024) specifically demanded steeper emissions reductions by 2030 and 2035 from major emitters to keep the 1.5 °C goal viable. 

Some of the high-emitting states that have profited from SIDS are those with a history of resource extractions, such as the United States and the United Kingdom. For example, the United States is the world’s largest historical emitter of carbon dioxide, while it faces serious consequences of sea-level rise in coastal areas, its vast inland territory and resources mean it does not face existential statehood loss like SIDS with a less contribution to global emissions.

Many of these states have also enabled private fossil fuel companies to operate with minimal regulation, thereby profiting from these activities while externalizing the environmental costs to SIDS. For example, States with high fossil fuel emissions, like Norway, Australia, and the United States enable private actors to profit at the expense of SIDS by granting new oil and gas exploration licenses, which directly contribute to global emissions without their government being held legally responsible for resulting harm to vulnerable states. 

To fight this injustice, SIDS have taken a range of legal and political actions. The Alliance of Small Island States (AOSIS) advocates for ambitious mitigation targets and a dedicated mechanism for ‘loss and damage’ finance, UN climate negotiations. In a notable diplomatic move, Palau launched a campaign at the UN General Assembly in 2011 to request a climate-related advisory opinion from the ICJ; however, they failed to gain enough support due to broader political and diplomatic obstacles. More recently, Samoa successfully sought an advisory opinion from the International Tribunal for the Law of the Sea, which affirmed states’ obligations to protect the marine environment from the effects of climate change. 

Despite their persistent efforts, the voices of SIDS have not received the legal or political weight they deserve. This underscores their position that climate change is a matter of fundamental legal rights and state responsibility, rather than a mere policy issue within a specific treaty regime. The 2025 ICJ advisory opinion is a crucial step toward rectifying this historical injustice by placing their arguments at the center. 

Redrawing the Boundaries of Responsibility

The ICJ advisory opinion marks a new chapter for SIDS in their fight for climate justice by providing an international legal platform for confronting the historical inequalities that have defined international climate law. The most prominent conclusions in the opinion were the Court’s rejection of the lex specialis argument, its recognition of the duty to prevent significant harm as erga omnes, as well as its affirmation of state responsibility for private actors. 

Lex specialis is a legal principle that a specific law on a subject takes precedence over a general law. (ICJ, Obligations of States in respect of Climate Change, Advisory Opinion, 23 July 2025, para 166.) During the advisory opinion proceedings, certain high-emitting countries, such as the United States, United Kingdom and China, relied on this argument to contend that climate obligations should be determined solely by the UN climate regime. This approach, if successful, would have limited the scope of their legal duties and shielded them from accountability under broader international law. 

In past climate justice litigation, this argument has also been brought to the table to narrow accountability to treaty-specific frameworks, excluding broader human rights or customary law obligations. For example, in the Urgenda Foundation v. State of the Netherlands (2015) case, the Dutch government initially argued that its obligations were limited to the European Union Emissions Trading System, which could be seen as a form of lex specialis, though the argument was rejected. 

By rejecting the lex specialis argument in the advisory opinion, the ICJ validated SIDS’ position that climate change is not just a matter of environmental treaties but a complex legal issue with roots in customary international law and human rights. This will be useful for SIDS in the future by allowing them to invoke a broader range of legal principles and sources, thereby strengthening their claims and increasing the legal pressure on high-emitting states. 

Secondly, the Court holds that the duty to prevent significant harm to the climate system and other parts of the environment from anthropogenic greenhouse gas emissions’ is erga omnes. This means that every state has a legal interest in ensuring the protection of the climate system for the benefit of all humanity (ICJ, Obligations of States in respect of Climate Change, Advisory Opinion, 23 July 2025, para 440). Therefore, in the climate justice fight, its designation as erga omnes provides a legal basis for any state to bring a claim against a high-emitting state, bypassing the need to prove a direct bilateral harm and empowering a collective legal front. The ICJ’s acceptance of erga omnes obligations makes it easier for SIDS to litigate because it removes the requirement to prove that they, as individual states, were directly and disproportionately harmed, allowing them to bring a claim on behalf of the international community. 

Furthermore, the Court affirmed state responsibility for the conduct of private actors (ICJ, Obligations of States in respect of Climate Change, Advisory Opinion, 23 July 2025, para 428.) This means that when fossil fuel corporations or other private entities within a state’s jurisdiction contribute significantly to transboundary harm, the state may be held responsible for failing to regulate them. This addresses the situation arising from the historical injustice, in which Global North states profited from exploiting the lands and resources of SIDS by allowing extraction, drilling, or emissions while displacing the burdens onto vulnerable communities. For example, phosphate extraction by colonial powers in Nauru and Banaba (Kiribati) devastated the environment, benefitting the United Kingdom, Australia, and New Zealand while leaving local populations displaced.

It must be noted that, despite the clarification on arguments about lex specialis and erga omnes nature of the duties related to climate change, the Advisory Opinion on Obligations of States in respect of Climate Change has limitations that might temper its immediate impact. The Court avoided specifying which countries are responsible for reparations, instead emphasizing that legal consequences for climate harm must be determined on a case-by-case basis. This approach leaves complex issues of causation and attribution unresolved and the practical challenges of calculating compensation and enforcing payments remain fraught with uncertainty. Additionally, some judges argued that the Court should have gone further by explicitly addressing state obligations to phase out fossil fuels. 

Nevertheless, the ICJ’s opinion will embolden civil society and affected communities to pursue litigation at the domestic and international levels, using the clear pronouncements on due diligence, human rights and state responsibility. The ICJ’s advisory opinions on climate change provide a more decolonial position by recognizing the transboundary harm caused by high-emitting states and private entities. Despite the non-binding nature of the advisory opinion, its authority lies in clarifying existing legal obligations, shaping how states and courts interpret international law, and setting a persuasive precedent that can influence future climate litigation and policy. 

Conclusion

The ICJ’s advisory opinion on climate change provides a significant legal tool for SIDS by validating key arguments long advanced by them. Specifically the opinion’s findings on three key points are critical for SIDS: rejection of lex specialis argument, recognition of erga omnes obligations regarding climate, and possibility of state responsibility for the actions of private entities. 

Although the advisory opinion is not legally enforceable, its influence is considerable. It carries a high degree of legal authority as a statement from the world’s highest court and acts in support of existing international legal statutes. Advisory opinions provide a legal basis for future climate litigation in domestic, regional, and international courts. For SIDS specifically, advisory opinions on climate change can serve as a powerful instrument to increase political pressure on states responsible for high levels of greenhouse gas emissions to adopt more ambitious climate policies. SIDS can leverage advisory opinions passed down from the ICJ, as well as other related international legislation, as a backbone to fight for financial reparations due to loss and damage sustained by climate change. An advisory opinion confirms that SIDS’ fight for climate justice is an effort to decolonize legal frameworks, which can empower their diplomatic and legal effort to challenge historical power imbalances and demand a more equitable system. 

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Glossary

• Alliance of Small Island States (AOSIS): A coalition of small island and low-lying coastal countries that work together to advocate for stronger climate protection against climate change.

• Climate Justice: The concept that those who have contributed least to climate change like SIDS, should not bear the greatest burden of its impacts, and that high-emitting states have a responsibility to act.

• Erga Omnes: An international law term that refers to obligations that a state owes to the international community as a whole, rather than just individual states.

• State Responsibility: The legal principle that states are accountable under international law for the actions or omissions that cause harm to other states or to the international community.

• Transboundary Harm: Damage that affects multiple countries or the global community as a whole. 

• UN Climate Regime: The system of international agreements, negotiations and institutions under the UN that guide action on climate change. It includes treaties such as the UN Framework Convention on Climate Change, the Kyoto Protocol, and the Paris Agreement.

• United Nations General Assembly: A UN body where all member states meet to discuss and make recommendations on international issues.