On 23 July 2025, the International Court of Justice (ICJ) delivered its long-awaited advisory opinion on the obligations of states in relation to climate change. The opinion was issued in response to a historic request by the United Nations General Assembly, following a campaign led by Vanuatu and other climate-vulnerable nations. The request posed two central questions: first, what are the specific legal duties of states under international law to prevent, mitigate, and respond to climate change? And second, what legal consequences arise when states, by act or omission, breach those duties, particularly where the harm disproportionately affects other countries and communities, including future generations?
For many Global South states, ranging from small island developing states like Tuvalu and Mauritius to economies like India and Pakistan, this request was more than symbolic. Their submissions to the Court framed climate inaction as a breach of international law, grounded in principles of equity, differentiated responsibility, and reparation. The precise legal arguments varied, but most of them called for an international legal order that recognizes historical injustice, enforces climate obligations, and ensures redress for those most affected.
The opinion was released just days after Pakistan experienced another round of catastrophic flooding. This event echoed the country’s legal submission and highlighted the very harms the Global South sought to raise through international law.
This blog critically examines how the ICJ responded to those calls. It assesses the extent to which the Court’s opinion affirms the core legal demands articulated by Global South states, namely, (1) binding legal accountability, (2) reparations, and (3) the operationalisation of differentiated responsibilities, and where it fell short. The Court delivered a strong doctrinal endorsement of states’ climate obligations, but it ultimately avoided substantive innovation or enforcement. The result is a cautious but significant opinion: one that confirms the law’s relevance to climate justice, but leaves its transformative potential largely unrealised.
Binding Legal Accountability: Affirmed in Principle, Constrained in Practice
The first question posed to the ICJ asked about states’ international legal obligations with regard to climate change. From the submission of the majority of the Global South, the answer was clear: climate action is not a matter of policy discretion, but of legal duty. In this regard, the Court’s opinion offers a strong doctrinal endorsement. It affirms that states are bound by a range of obligations drawn from multiple legal sources:
- Treaty law, including the UN Framework Convention on Climate Change (UNFCCC), the Kyoto Protocol, and the Paris Agreement;
- Customary international law, including the no-harm rule and the duty to prevent significant transboundary harm; and
- Relevant human rights instruments, where climate impacts infringe upon rights to life, health, food, water, or cultural identity (paras. 172–173, 200–202, 268–270).
Crucially, the Court distinguishes between two types of obligations:
- Obligations of conduct, which require states to adopt mitigation and adaptation measures in line with scientific standards and evolving capabilities; and
- Obligations of result, which relate to actual outcomes, such as emissions reductions or preservation of ecological systems (paras. 203–208).
Both are recognised as legally binding. The Court rejects the idea that states can invoke national discretion or capacity constraints as a defence for non-compliance, emphasising that obligations must be construed and applied in good faith (para. 205).
This section of the opinion represents a partial vindication for many Global South states, for instance, Pakistan stressed in its submission that legally enforceable obligations, not voluntary pledges, are important for preserving the credibility of international climate governance. Tuvalu made a similar argument, explicitly calling for clear legal duties that hold high-emitting countries accountable. Madagascar, while more cautiously phrased, also emphasised the need for clarity and legal certainty to ensure sustained cooperation. The ICJ appears to have accepted this premise by not treating international climate law as mere soft law, but as a framework containing real and enforceable legal duties derived from treaties, custom, and broader principles of international law.
However, the opinion also reflects the Court’s institutional caution. It outlines the legal architecture of climate obligations in detail, but it does not identify any specific state that is currently in breach. Nor does it assess whether existing national commitments, such as nationally determined contributions under the Paris Agreement, are legally sufficient. In paras. 106–110 and 445, the Court restates that it is not rendering a contentious judgment, and thus cannot attribute wrongful conduct to particular states.
This leaves a conceptual gap between recognition and responsibility. Climate obligations are declared binding, but no path is offered for determining when, or by whom, they have been violated. The ICJ confirms that breaches of these duties may engage state responsibility, but stops short of setting standards for such findings or recommending institutional pathways for enforcement (para. 420).
Reparations: Recognised in Doctrine, Restrained in Access
The second question before the Court concerned legal consequences, in response to which, the ICJ reaffirmed a central tenet of international law that breaches of legal obligation must be remedied. States found responsible for wrongful conduct are required to make full reparation, including restitution, compensation, and satisfaction, consistent with the rules codified in the Articles on the Responsibility of States for Internationally Wrongful Acts (ARSIWA) (paras. 418–420, 449–455).
This doctrinal recognition offers legal clarity sought by many Global South submissions. Vanuatu, for example, called for recognising the breach of erga omnes obligations and demanded a framework for compensation and satisfaction that reflected both direct harm and non-economic loss. Pakistan, while less focused on technical reparations, strongly linked disproportionate climate impacts to the legal principle of equity and the need for meaningful redress.
The Court did not reject these claims but confirmed that harm to the environment itself, not merely human life or economic interests, is a legally relevant injury that may give rise to reparation (para. 451). It also acknowledged that obligations breached in the climate context can, in some cases, be erga omnes, meaning that all states, not just directly injured ones, may have a legal interest in ensuring remedy (paras. 443–454). These findings strengthen the position of small and vulnerable states seeking standing in future legal fora, including regional human rights bodies and international claims tribunals.
However, the path from breach to remedy remains legally arduous. In para. 436, the Court reaffirms that any claim for reparation must establish a “sufficiently direct and certain causal nexus” between the wrongful act and the harm suffered. This standard, drawn from traditional state responsibility doctrine, poses significant challenges in the climate context. Harm from climate change is cumulative, cross-border, and probabilistic, making it difficult for affected states to isolate and attribute specific damage to the conduct of individual emitters.
States such as Bangladesh and Madagascar had explicitly asked the Court to take these scientific and evidentiary complexities into account. Madagascar, in particular, urged the Court to adapt existing rules to accommodate indirect harms and cumulative causation, acknowledging that vulnerable states cannot always produce “smoking gun” evidence. Yet the Court declined to lower or adjust the standard. While sympathetic in tone, its reasoning remains rooted in a traditional model of legal injury that requires rigorous, state-specific proof.
This evidentiary burden leaves many Global South states in a precarious position. They now have a clear legal basis for claiming reparations, but face procedural and scientific thresholds that are difficult to satisfy in practice. In real terms, this means that while climate reparation is possible under international law, it remains largely inaccessible without further legal innovation or political negotiation.
The Court’s treatment of the Loss and Damage mechanism under the Paris Agreement reinforces this restraint. In paras. 414–415, the Court describes the Loss and Damage Fund as a cooperative, facilitative tool, not as a reparations mechanism grounded in legal liability. This interpretation aligns closely with the position of countries like the United States, which have resisted efforts to frame climate finance as reparative or compensatory. While the Court does not foreclose future legal developments in this area, it consciously avoids politicising the Fund or linking it to a duty to compensate.
Differentiated Responsibility: Formally Affirmed, Substantively Deferred
Among the most longstanding demands from the Global South has been that climate obligations must reflect not only present capacities, but also historic responsibility and entrenched developmental disparities. This principle, codified in the phrase common but differentiated responsibilities and respective capabilities (CBDR-RC), has shaped the architecture of climate treaties since the UNFCCC. Yet the question before the Court was on the existence of this principle, but the legal weight’s affirmation, and the court’s guidance on how it should function across obligations were questioned. The answer is a qualified yes.
The ICJ expressly affirms CBDR-RC as a “cardinal principle” of international environmental law and recognises that differential treatment is not simply a matter of policy equity or diplomatic compromise; it is a legally relevant standard that informs the interpretation and application of states’ obligations under both treaty and customary law. (paras. 148–151,179–180). This affirmation marks an important doctrinal win for Global South states, many of whom had stressed that a uniform application of climate obligations would undermine justice. Submission from China, for instance, argued that mitigation and adaptation efforts must be proportionate to states’ historical emissions, technological capacity, and development needs.
The ICJ does not shy away from these arguments and confirms that CBDR-RC applies to both obligations of conduct and result, and that equity must shape both the design and implementation of climate duties. In doing so, the Court reiterates that “states cannot be treated identically in the application of international law where their circumstances differ significantly” (para. 150).
However, the Court’s affirmation is entirely at the level of principle as it abstains from detailing what differentiated responsibility means in practice. It does not assign minimum emissions reductiontargets for developed states, nor does it exempt developing states from certain obligations. Nor does it interpret CBDR-RC as requiring binding financial transfers, technology support, or legal carve-outs. Instead, it leaves these determinations to states themselves and the institutional mechanisms of the UN climate regime (paras. 250–254, 291–292).
This is precisely where the opinion diverges from the stronger demands voiced by several Global South actors. China, for example, argued that developed states should bear primary legal and financial burdens for mitigation, and that developing states should not be held to the same standard of accountability. Tuvalu framed climate inaction by major emitters as a breach not just of environmental law but of intergenerational justice, warranting enforceable differentiation. While the Court acknowledges the relevance of these arguments, it declines to prescribe how such responsibility should be allocated.
The opinion thus preserves the political status quo: CBDR-RC is real, but its implementationremains subject to negotiation, not legal determination. The ICJ affirms that equity must shape climate law, but offers no mechanism to ensure that equity is realised in practice.
Conclusion
The ICJ’s 2025 advisory opinion affirmed that climate obligations are not just aspirational but are binding duties under international law. States must mitigate harm, cooperate in good faith, and act with due diligence. Breaches, the Court confirms, can give rise to legal consequences, including reparation. However, the opinion also reveals the limits of law in practice. It avoids naming violators, refrains from defining thresholds for compliance, and upholds a high causation bar for reparations, one that few vulnerable states can realistically meet. Differentiated responsibilities are acknowledged but left vague. The Loss and Damage mechanism is noted but not treated as liability-based.
References
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- UN General Assembly Resolution A/RES/77/276 https://docs.un.org/en/A/RES/77/276 accessed 24 July 2025
- Al Jazeera, ‘Why is Pakistan so vulnerable to deadly flooding?’ (17 July 2025) https://www.aljazeera.com/news/2025/7/17/why-is-pakistan-so-vulnerable-to-deadly-flooding accessed 24 July 2025
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- ILC, Articles on Responsibility of States for Internationally Wrongful Acts (2001) https://legal.un.org/ilc/texts/instruments/english/draft_articles/9_6_2001.pdf accessed 24 July 2025
- ICJ, Document No. 187-20240325-wri-01-00-en https://www.icj-cij.org/sites/default/files/case-related/187/187-20240325-wri-01-00-en.pdf accessed 24 July 2025
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