Author: Anish Tandi
College: Centurion University, Bhubaneswar
LinkedIn Profile Link: www.linkedin.com/in/anish-tandi-668a7b2a1
ABSTRACT
Over the Last two years, the world has seen an unprecedented judicialization of international climate law. These decisions by the international Tribunal for the law of the Sea (ITLOS), the Inter-American Court of Human Rights (IACtHR), and the International Court of Justice (ICJ) shifted the paradigm of international climate law. Apart from confirming that human GHG emissions are marine pollution under the law of the Sea Convention (UNCLOS), confirming that states inadequate climate actions violate their human rights obligation, and establishing Binding Customary International Law duties on States to address climate change, these decisions are effective. They are already affecting domestic legislation, corporate responsibility, and international negotiations in the host of climate cases registered so far (3,099 as of June, 2025) in courts worldwide.
TO THE POINT
The climate crisis, which the ICJ describes as “an existential problem of planetary proportions”, has moved from the stage of political negotiations to that of adjudication before numerous international tribunals and courts. Across these regional and international jurisdictions, three landmark judicial opinions issued in 2024-2025 redefined States legal obligations with respect to climate change. The ITLOS Advisory Opinion clarified that the unabsorbed GHGs taken up by the sea may be considered “pollution” under the United Nations Convention on the Law of the Sea (UNCLOS), thus bespeaking an immense due diligence criteria on the part of States Parties to avoid, mitigate and control this pollution. The IACtHR Advisory Opinion OC-32/25, meanwhile, elevated to the status of a new human right to a healthy climate, established that the duty to avoid irreversible environmental damage has attained the status of jus cogens, and recognized Nature as a rights-holder in its own right. Most importantly, the ICJ Advisory Opinion, issued on 23 July 2025, demonstrated that the legal authority of States climate change commitments stems not only from climate treaties but from myriad sources principally customary international law, human rights law, and the law of the sea. The Court found that States are enjoined to act with due diligence to realize the globally agreed 1.5 degrees Celsius climate target and stated that violations of the due diligence obligation may give rise to State responsibility, and ultimately the duty to repair.
USE OF LEGAL JARGON
The jurisprudence deriving from these holds traverse difficult doctrinal ground, engaging basic principles of international law including erga omnes obligations, state responsibility and the doctrinal of due diligence. The ICJ relied on the reports of the International Law Commission (2001) to clarify that breaches of obligations under the UNFCCC could generate the “full range of legal consequences” including restitution, compensation and satisfaction. The court’s usage of the principles of lex specialis was particularly interesting, the court dismissed the argument that the climate change regime constituted a sui generis legal order subjugating that other rules of international law, holding instead that the obligations under the UNFCCC and Paris Agreement should be understood as ‘mutually supportive’ with other obligations of general international law. The tribunal between ITLOS and the Parties also used the principles of “systemic integration” enshrined in article 31(3)(c) of the Vienna Convention on the Law of Treaties to read UNCLOS in light of external climate treaties and the “best available science” compiled in the IPCC reports. The IACtHR’s acknowledgement of the obligation to prevent irreversible environmental harm as a jus cogens norms is especially significant, heaving the effect of placing this duty on an elevated pedestal from which no derogation is possible. These opinions set out how due diligence in relation to climate change is to be conceived through the notion of “obligations to take all appropriate measure, including ‘reasonable measures’, and ultimately stringent and enhanced measures proportionate to the severity of the threat”.
THE PROOF
The Scientific basis for these judicial findings based on the definitive scientific consensus set out by the Intergovernmental Panel on Climate Change (IPCC). The ICC formally met with IPCC Scientists and came to the conclusion that the “reports are the best available science on the causes, nature and effects of climate change”. It found that “it is scientifically established that the increase in concentration of GHGs in the atmosphere is mainly caused by human activities and that “liveable climate and other environmental systems have already experienced significant damage as a result of human activity”. This scientific position addresses causation and attribution issues.
The ICJ was explicit that causation of damage only needed to be established for the purpose of the appropriate measures of reparation and not responsibility itself. The Court was also willing to take a nuanced approach to causality and distinguish between (1) establishing whether a climatic event can be attributed to climate change given the state of scientific knowledge and (2) determining whether the harm is attribution to one state, or a group of States, in concreto. The Court also confirmed that attribution is possible and that a state’s failure to prevent such an outcome by undertaking actions including through fossil fuel production, fossil fuel production, fossil fuel consumption, the granting of fossil fuel exploration licenses or the prevention of fossil fuel subsidies, can amount to an internationally wrongful act attributable to that state. Moreover, it was found that even if a state had not directly perpetrated the injury, it could still have failed to take care to prevent injury by private actors within its jurisdiction, thus holding states responsible for the activities of private corporations in addition to responsibility for the actions of States.
The extent to which climate litigation is growing demonstrates the practical relevance of these developments. The Global Climate Litigation Report 2025 by the UNEP and Sabin Centre lists 3,099 climate-related cases filed in 55 national jurisdictions and in 24 international or regional entities. While the US continues to be the most prevalent jurisdiction with 1986 cases, the presence of the Global South is evident with 305 cases. Cases against governments tend to revolve around implementation of climate commitments, climate rights and leaving fossil fuels in the ground and cases against corporates tend to revolve around liability for damages, greenwashing and disclosure of financial information.
CASE LAWS
1. International Tribunal for the Law of the Sea (ITLOS) Advisory Opinion on Climate Change and International Law (2024)
This landmark opinion sought by the Commission of Small Island States on Climate Change and International Law (COSIS), it clarified that human-generated GHG emissions taken up by ocean in the form of “pollutants” within Article 194 of the UNCLOS. The Tribunal found that states parties have stringent due diligence obligations to prevent, reduce and control pollution of the marine environment and to protect and preserve the environment from adverse effects of climate change. The Opinion found that States have to take “all measures necessary” in conformity with relevant international standards (including that of the Paris Agreement), and highlighted the role of the 1.5 degrees Celsius limit in defining the content of the obligations.
2. Inter-American Court of Human Rights Advisory Opinion OC-32/25 on the climate Emergency and Human Rights (2025)
In its most participatory advisory proceeding ever, the IACtHR made comprehensive climate pronouncements under the American Convention on Human Rights. The Court defined the right to a healthy climate as an autonomous human right, held the obligation to avoid irreparable harms to the environment has acquired the jus cogens norm, and acknowledged Nature as a rights holder. It articulated the requisite of “enhanced due diligence” under which Governments must undertake tangible, science-based policies to progressively reduce GHGs, establish caps for direct emitters, and safeguard vulnerable communities. The Court invoked the pro actione rule to facilitate climate litigation, acknowledging collective standing and extraterritorial jurisdiction in climate actions.
3. International Court of Justice Advisory Opinion on the Obligations of States in Respect of Climate Change (2025)
The ICJs unanimous holding is perhaps the highest level of judicial authority on international climate law. It found, that states obligations come from a number of different legal sources climate treaties, customary international law, the law of the sea, other environmental treaties and human rights law and dismissed the proposition that the climate change regime as lex specialis. It reaffirmed the obligation of States to exercise due diligence in order to ensure they approach the 1.5 degrees C temperature goal, that the duty to prevent harm is part of customary international law, that the breach of that obligation gives rise to state responsibility and compensation, and that UNCLOS maritime baselines are maintained notwithstanding rising sea levels, echoing the existential concerns of small islands states.
4. European Court of Human Rights, Verein KlimaSeniorinnen Schweiz v. Switzerland (2024)
In this controversial case, the Grand Chamber of the European Court of Human Rights found that inadequate climate action could be violation of the right to respect for private and family life under Article 8 of the European Convention. It required States to introduce binding targets to reduce emissions in line with the science and articulated the essential objective of carbon neutrality by 2050. The Judgement, delivered at the same time as the international advisory opinion, marked the first occasion on which a human rights court identified a State’s human rights breaches through inadequate climate action, creating a human rights-based obligation to respond to climate change.
CONCLUSION
In each of their advisories, the ICJ, IACtHR and ITLOS all proclaimed the legally authoritative nature of the 1.5 degrees C temperature target, and rogeneralized the legal applicability of the Paris goal to all States of just eighteen months provides a decisive paradigm shift in the applicability if international law to climate change. The ICJ’s interpretation of the 1.5 degrees C goal to be a legal marker could substantively influence the contest of states NDCs, outlines, implementation structures and policies. Lastly, the declarations underpinning the notion that GHG emissions are marine pollution turn the legal determination of responsibility from a reflection of climate science to a principle all States Parties are expected and required to abide by.
Consequences of the decisions are profound. Firstly, the decisions will influence national legislation and regulatory framework, inform reasoning of domestic courts and bolster the bargaining power of States most affected by the climate crisis in upcoming COP negotiations. For private actors, recognition of states responsibility to regulate private sector activity on climate change indicates increased regulatory risk and liability for insufficient climate governance. The ICJ further clarified that causation is not necessary to find State responsibility and is only a requirement for reparations lowering the bar for climate claims, yet complicating attribution debates in the interim.
Notwithstanding, hurdles persist. Advisory opinions do not have binding legal effect and their implementation is contingent upon political will and enforcement mechanisms at the national level. The ICJ refused to indicate to the question of how responsibility and reparation might work in situations where the original damage has already been caused or is unavoidable something that is particularly concerning to small island developing Sates. The relationship between the many relevant bodies of law including human rights and climate change law, requiresfurther doctrinal elaboration. That said, the opinions mark a climactic judicial intervention that translates abstract constitutional principles into concrete that through responsibility they hold States and accountability to their legal obligations in the critical challenge of our age.
FAQs
Q1. What is the legal significance of the ICJ’s advisory opinion on climate change?
Although the ICJ’s advisory opinion is legally non-binding, it is by far the most authoritative judicial statement on the internation obligations of States to address climate change. It states that the obligations arise from a multitude of sources including climate treaties, customary international law, human rights law and law of the sea. The advisory opinion concludes that violations of climate obligations can give rise to State responsibility including the obligation to compensate. The findings of the ICJ will have profound influence on national legislation, domestic courts and international negotiations.
Q2. How have international courts established a link between climate change and human rights?
Both the IACtHR have acknowledged the human right to a healthy climate as an autonomous human right, climate violates the rights to life, health, housing and a healthy environment. The European Court of Human Rights, in the KlimaSeniorinnen, found that potentially inadequate climate action might infringe on Article 8(respect for private and family life) of the European Convention on Human Rights and that states have a core obligation to protect these through adequate climate action.
Q3. What does the recognition of jus cogens status for environmental obligations mean?
The IACtHR noted that the due diligence obligation to ensure that irreversible damage to environment can no longer derogate peremptory norm of jus cogens. A state party cannot itself derogate from its obligation. This has the erga omnes effect that every State can invoke the responsibility of a state, not just the state, which has suffered the damage.
Q4. What are the implications for private actors and corporations?
The opinions affirm that states have a duty to regulate private actors effectively. Failure to exercise due diligence regarding private actors GHG emissions may constitute an internationally wrongful act attributable to the state. This will likely lead to more stringent domestic regulation, increased corporate liability for greenwashing and climate-related financial disclosures, and potential investor-state claims.
Q5. How will these opinions affect the upcoming CO030 negotiations?
These opinions bolster the negotiations position of climate-vulnerable States by affirming that mitigating climate change is a legal obligation that state parties accepted under international law. Low-emitter countries can now point to a legal responsibility to require high-emitter states to respond and provide climate action and support for these most at risk. Thanks to these judicial pronouncements, the legal obligations of states exist on counteracting climate change through mitigation, adaptation, and finance, thus raising the level of information in negotiations on equity, justice and loss and damage.
REFERENCES
1. United Nations Environment Programme and Sabin Centre for Climate change Law, Global Climate Litigation Report: 2025 Status Review (2025).
2. International Court of Justice, Advisory Opinion on the Obligations of States in Respect of Climate Change (23 July 2025).
3. International Tribunal for the Law of the Sea, Advisory Opinion on Climate Change and International Law (21 May 2024).
4. Inter-American Court of Human Rights, Advisory Opinion OC-32/25 on the Climate Emergency and Human Rights(29 May 2025).
5. European Court of Human Rights, Verein KlimaSeniorinnen Schweiz and others v. Switzerland(2024).
6. International Law Commission, Articles on Responsibility of States for Internationally Wrongful Acts (2001).
