Climate Justice at The Hague: Unpacking the ICJ's Landmark Opinion

The escalating climate crisis presents an urgent and existential threat to humanity, imperiling all forms of life and the very health of our planet. In this context, the role of international law and institutions in compelling states to act has become a focal point of global discourse. The recent International Court of Justice (ICJ) advisory opinion on states' obligations regarding climate change marks a pivotal moment, offering a profound legal and moral pronouncement on this critical issue. This report delves into the transformative potential of this ruling, examining its implications through the contrasting lenses of realism and liberal internationalism. These two dominant theories of international relations offer fundamentally different perspectives on state behavior, the efficacy of international law, and the prospects for global cooperation. By analyzing the ICJ's opinion through these theoretical frameworks, a nuanced understanding of its likely impact on the complex landscape of climate governance can be gained, inspiring hope and optimism for the future.  

While the ICJ's advisory opinion is not legally binding in the same way as a contentious judgment, its significance extends far beyond a simple formal classification. As the principal judicial organ of the United Nations, the Court's pronouncements carry immense legal authority and prestige. This advisory opinion makes a significant contribution to the development of international law, influencing the interpretation of existing treaties and potentially fostering the emergence of new customary international law. This process, where even non-binding pronouncements from highly authoritative judicial bodies shape the legal consciousness of states and international actors, creates a new normative environment. This dynamic aligns with liberal internationalist theories that emphasize the gradual evolution of international norms and their capacity to influence state behavior over time, even without direct enforcement. The opinion's role in fostering this normative evolution is a central theme in understanding its potential impact.  

However, the question of whether this ruling will translate into concrete action immediately highlights the inherent tension between legal authority and political will in global governance. Realism posits that states retain their sovereign power and often prioritize perceived national interests above external mandates. The research indicates that major emitters such as the United States and Russia are staunchly opposed to the Court mandating emissions reductions. This direct opposition highlights the challenge of translating international legal pronouncements into universal compliance when powerful states perceive a conflict with their core interests. The dynamic and often contradictory forces that will determine the ultimate impact of the advisory opinion form a central analytical challenge for this report. Moreover, the potential difficulties in implementing the opinion, such as the need for robust monitoring and enforcement mechanisms, the role of non-state actors in holding states accountable, and the potential for legal disputes over the interpretation and application of the opinion, are essential considerations in understanding its implications.  

The ICJ's Pronouncement: Clarifying International Obligations and Rights

On July 23, 2025, the International Court of Justice delivered its long-awaited Advisory Opinion on the Obligations of States in Respect of Climate Change. This landmark opinion was requested by the United Nations General Assembly, the main deliberative, policymaking, and representative organ of the UN, in 2023, following years of lobbying by vulnerable island nations, such as Vanuatu, and was backed by over 130 countries. The Court was tasked with answering two critical questions: What are countries obliged to do under international law to protect the climate and environment from human-caused greenhouse gas emissions, and what are the legal consequences for governments when their acts, or lack of action, have significantly harmed the climate and environment?  

The Court's unanimous opinion, spanning over 500 pages, unequivocally stated that if countries fail to take appropriate measures to protect the planet from climate change, they could violate international law. President Yuji Iwasawa emphasized that "failure of a state to take appropriate action to protect the climate system may constitute an internationally wrongful act". The opinion clarified that states have an obligation under international law to reduce greenhouse gas emissions and contribute to climate change mitigation and adaptation. This includes duties for developed nations to cooperate on achieving the objectives of the United Nations Framework Convention on Climate Change, particularly through the transfer of technology and financial support. The Court also underscored that the mere preparation of nationally determined contributions (NDCs) under the Paris Agreement is insufficient; their content must be capable of achieving the Agreement's temperature goal and represent the highest possible ambition.  

A crucial element of the ruling is its affirmation that a "clean, healthy and sustainable environment" is a fundamental human right, essential for the enjoyment of all other human rights. This recognition, which developing countries have long campaigned for, paves the way for new legal actions, including states holding each other to account before the ICJ and domestic lawsuits. Notably, the Court specified that obligations under customary international law apply to all states, regardless of their adherence to specific climate treaties, such as the Paris Agreement. This is particularly relevant in light of instances such as the United States' withdrawal from the Paris Agreement. The explicit grounding of obligations in general international and customary law, coupled with the recognition of a human right to a clean, healthy, and sustainable environment, profoundly broadens the legal bases for climate action. This implies that states cannot simply opt out of specific climate treaties to avoid obligations, as customary international law applies universally, irrespective of treaty ratification. Moreover, linking climate change to human rights opens up new avenues for litigation at domestic and regional levels, leveraging existing human rights jurisprudence. This represents a deliberate effort by the Court to empower a broader range of actors and legal systems to pursue climate accountability, a strategy consistent with liberal internationalist approaches to overcoming the limitations of state-centric enforcement. The ruling's potential impact on the Paris Agreement, particularly in terms of increasing the pressure on states to fulfill their obligations and the potential for legal challenges against states that fail to do so, is a key aspect of its implications.  

Furthermore, the opinion stated that countries harmed by climate change could be entitled to reparations for damages suffered due to rising global temperatures, to be determined on a case-by-case basis. It clarified that breaches of climate obligations could give rise to "full reparations," including halting harmful actions, providing financial compensation for losses, and even requiring an immediate cessation of greenhouse gas emissions above a science-based safety threshold. The Court's message was clear: "the production, consumption and granting of licenses and subsidies for fossil fuels could be breaches of International Law". This decision adds to the global momentum towards climate accountability, reinforcing the "Polluter Pays" movement. While the opinion acknowledges "national circumstances" and "contribution to cumulative GHG emissions" in determining ambition and calls for technology and financial transfers from developed nations, its strong emphasis on universal obligations under customary international law and the potential for reparations for any state failing to act subtly challenges the traditional interpretation of "common but differentiated responsibilities" (CBDR). Historically, the CBDR principle has allowed developing nations to argue for less stringent obligations based on their historical emissions and development needs. While not explicitly overturning the CBDR, the opinion places a more substantial and universal legal burden on all states to protect the climate system, potentially narrowing the scope for inaction based solely on historical responsibility or development status. This creates a new legal dynamic in climate negotiations, prompting all states to take greater accountability.  

Realism's Lens: State Sovereignty, National Interest, and the Limits of International Law

Realism, a dominant school of thought in international relations for nearly a century, posits a world where global politics are fundamentally anarchic, lacking a central authority above sovereign states. States are considered the primary, rational, and unitary actors, prioritizing their national security and survival above all else. Within this framework, power, often defined in terms of military capabilities, is the key determinant of state interactions, leading to a constant struggle for influence and a competitive, conflictual nature of global politics. Realists are inherently skeptical of international law and institutions, viewing them as secondary to state interests and ultimately unable to compel behavior without the backing of state power.  

From a traditional realist perspective, the ICJ's advisory opinion, being non-binding, would be seen as having limited practical effect on state behavior. States, particularly major greenhouse gas emitters like the United States and Russia, have already demonstrated staunch opposition to any court-mandated emissions reductions, viewing such external mandates as infringements on their sovereignty and national economic interests. The pursuit of national interest, which may involve prioritizing economic growth and resource exploitation, often takes precedence over global environmental goals. This is underscored by the "relative gains problem," where states are concerned not just with their absolute benefits from cooperation, but also with how much other states might gain in comparison, fearing a shift in the balance of power.  

Traditional realism, with its focus on military power and interstate conflict, struggles to account for diffuse, non-traditional threats, such as climate change, fully. However, an evolving strand of realist thought, sometimes referred to as "climate realism" or "defensive realism," offers a more nuanced perspective on climate change cooperation. This view acknowledges climate change as a "threat multiplier" and a direct national security risk, leading to potential interstate conflict over dwindling resources, mass migration, and instability. From this perspective, even a hard-nosed realist might support international cooperation on climate change if the benefits of cooperation are so considerable that they overcome the relative gains problem, effectively framing climate action as a necessary measure for state survival and the protection of national interests. This approach emphasizes investments in resilience, adaptation, and competitive clean technology industries to safeguard American interests in a warming world.

This internal adaptation within realist thought redefines climate change as a direct security concern, thereby providing a realist justification for states to engage in climate action and even cooperation. This is not cooperation driven by altruistic reasons or shared norms, but instead by self-interest and the pursuit of national security in a changing threat landscape. This illustrates that while realism's core tenets remain, their application to new global challenges can lead to surprising policy prescriptions, moving beyond outright dismissal of climate action.  

Realism strongly emphasizes state sovereignty. Developing nations, in particular, express fears of "erosion of their sovereignty through climate change action and response mechanisms," viewing it as "interference in internal policies". Yet, the ICJ opinion, although non-binding, explicitly states that "failure of a state to take appropriate action to protect the climate system may constitute an internationally wrongful act." This creates a paradox. While states assert sovereignty to resist external mandates, their inaction on climate change can itself be deemed an internationally wrongful act, potentially leading to reparations. This suggests that the traditional notion of absolute sovereignty is increasingly challenged by the transboundary nature of climate impacts and evolving international legal norms, forcing states to reconcile their autonomy with their global responsibilities.  

Liberal Internationalism's Vision: Cooperation, Institutions, and the Pursuit of Collective Action

In stark contrast to realism, liberal internationalism advocates the belief that international progress is achievable through increasing levels of harmonious cooperation among political communities. This theory emphasizes the crucial role of international institutions, open markets, and cooperative security in transforming world politics from anarchy to a system governed by common institutions and the rule of law. Liberal internationalists argue that states can achieve mutual or "absolute gains" through collaboration, and that it is often in their national interest to cooperate, even on complex transnational problems like climate change.  

The liberal internationalist framework explains the very existence and evolution of international climate governance regimes, such as the United Nations Framework Convention on Climate Change, the Kyoto Protocol, and the Paris Agreement. These institutions provide the processes and arenas for state interaction, facilitating diplomacy, negotiation, and collective action. The theory posits that increased interdependence between sovereign states, driven by advancements in communication and transportation, further incentivizes cooperation, as states are less likely to engage in conflict if they have strong economic ties.  

From a liberal perspective, the ICJ's advisory opinion is a significant validation and strengthening of international law's capacity to address global challenges. Even as a non-binding opinion, its immense legal weight and moral authority are seen as crucial in shaping legal precedents and influencing future jurisprudence. It provides a clear legal interpretation of states' obligations, which can then be leveraged by multilateral organizations, such as the United Nations, as well as by civil society organizations, to press for greater accountability and policy shifts. The emphasis on a "clean, healthy and sustainable environment" as a human right aligns perfectly with liberal values of individual freedom and human dignity, providing a powerful normative basis for collective action.  

Liberal institutionalism posits that international institutions can mitigate anarchy and promote cooperation by establishing norms, rules, and frameworks that guide the behavior of states. The ICJ opinion, by clarifying existing international legal obligations and affirming new human rights related to the environment, directly reinforces this theoretical premise. It provides a robust legal framework and a set of norms that can guide state behavior and facilitate collective action. The unanimous delivery of the opinion and the backing of over 130 countries further demonstrate a broad international consensus on these norms, which is a key liberal indicator of institutional strength and potential for change. This illustrates how the opinion provides tangible, real-world support for the liberal internationalist worldview.  

Liberalism encompasses the "democratic peace theory," which posits that democracies rarely engage in war with one another and tend to prioritize internal stability. However, the ICJ opinion and the broader climate crisis highlight a tension within the application of this theory to global environmental issues. While democracies may foster peace among themselves, some major democratic emitters, such as the United States, have historically resisted stringent climate action or even withdrawn from international agreements. This resistance often stems from perceived national economic interests or interpretations of individual freedoms that conflict with collective environmental responsibilities. This challenges the simplistic notion that democratic governance automatically translates into robust international climate cooperation, suggesting that domestic political dynamics and varied interpretations of liberal principles can still impede collective action, even when a clear international legal framework is provided.  

The Nexus of Theory and Practice: Assessing the ICJ Opinion's Potential for Change

The ICJ's advisory opinion presents a fascinating case study for the enduring debate between realism and liberal internationalism regarding the effectiveness of international law. From a liberal internationalist perspective, the opinion represents a monumental step forward, signaling a "new era of climate accountability at a global level." Its clarification of existing obligations under customary international law, beyond specific treaties, and its explicit recognition of the human right to a healthy environment, provide powerful legal tools for future climate litigation and policy development. This normative shift, reinforced by the Court's authority and prestige, is expected to "spark a chain reaction that accelerates climate litigation on a global scale", influencing domestic courts and international political processes.  

Realists, however, would remain skeptical of the opinion's immediate, direct impact on state behavior, given its non-binding nature and the persistent primacy of state sovereignty and national interests. They would point to the historical examples of powerful states resisting international frameworks or failing to comply with non-binding pronouncements when perceived national interests are at stake. The opposition from central petroleum-producing states, such as the United States and Russia, to court-mandated emissions reductions exemplifies this realist stance, where economic and strategic considerations often outweigh international legal or moral imperatives.  

Yet, the practical implications of the ICJ opinion extend beyond a simple dichotomy between binding and non-binding, revealing a dynamic interplay between the two theories. While direct enforcement by the ICJ is limited, the opinion's comprehensive legal analysis provides a robust foundation for "decentralized" enforcement through domestic and regional courts. Previous successful climate litigation cases in the Netherlands, Europe, and the Inter-American system demonstrate that human rights-based arguments and duties of care can compel governments to act. The ICJ opinion significantly strengthens the legal basis for such cases globally.  

The research repeatedly highlights that the ICJ opinion "paves the way for other legal actions, including states returning to the ICJ to hold each other to account as well as domestic lawsuits," and "will guide climate litigation at the local, regional, and national courts." This indicates a crucial mechanism for impact: the ICJ, rather than directly enforcing, provides powerful legal arguments or a lever for other actors to use. This includes domestic courts, regional human rights courts, which have already demonstrated success in climate-related cases, and civil society organizations. This multi-level approach to governance, where international legal norms are translated and enforced at sub-state levels, is a key liberal internationalist pathway for change that realists often overlook, demonstrating how international law can have pervasive, indirect influence.  

Realists define national interest primarily in terms of power and security. Traditionally, climate change was often relegated to "low politics," secondary to military threats. However, the ICJ's framing of climate change as an "urgent and existential threat to humanity" and the "climate realism" argument that it is a "threat multiplier" suggest a fundamental reevaluation of what constitutes "national interest." If climate change directly imperils a state's survival, resources, and stability, then even a realist state may find it pragmatic to cooperate, not out of idealism, but out of necessity. This dynamic indicates a potential convergence of realist and liberal motivations for climate action, driven by the sheer scale of the threat, thereby creating a new impetus for change.