Climate change may sound like a subject for scientists and policymakers. But in July 2025, it became a major question of international law.
On 23 July 2025, the International Court of Justice (ICJ) gave its advisory opinion on States’ obligations in relation to climate change. The issue reached the Court after years of efforts by Pacific island countries and young climate activists, with Vanuatu playing an important role in bringing the question before the international community.
For a CLAT PG aspirant, this opinion is important because it connects several topics from Public International Law that you already study, including Article 65 of the ICJ Statute, advisory opinions, international treaties, customary international law, State responsibility, erga omnes obligations, human rights and the law of the sea.
So, what did the ICJ actually say about what countries are legally required to do to tackle climate change?
How did the question reach the ICJ?
In March 2023, the UN General Assembly adopted Resolution 77/276 and asked the ICJ to give an advisory opinion on climate change.
The basic questions were:
- What are States legally required to do to protect the climate system from greenhouse gas emissions?
- What are the legal consequences when States cause significant harm to the climate system through their acts or omissions?
The proceedings attracted participation from a very large number of States and organisations. The hearings were held at the Peace Palace in The Hague in December 2024.
The Court’s task was therefore not simply to ask, “Is climate change bad?” It had to answer a much more legal question: What does existing international law require States to do about it?
But can the ICJ even give such an opinion?
This is where Article 65 of the ICJ Statute becomes important.
Under Article 65, the Court may give an advisory opinion on a legal question when the request comes from an authorised UN body. Article 96 of the UN Charter gives the General Assembly and Security Council the power to request advisory opinions on legal questions.
The Court therefore had to consider whether the climate questions were actually legal questions.
The answer was yes.
The fact that climate change involves science, economics and politics does not stop a question from being a legal question.
An advisory opinion is generally not binding in the same way as a judgment in a contentious case. However, advisory opinions can have considerable legal importance because they clarify how international law should be understood.
Think of cases such as Reparation for Injuries, Namibia, Western Sahara, The Wall and Chagos. Advisory opinions are not simply “advice” that can be ignored without consequence.
Did the Court say climate treaties are the only law that matters?
No. This was one of the most important parts of the opinion.
Some States argued that climate change should primarily be dealt with under the special climate treaty regime, particularly the UNFCCC, Kyoto Protocol and Paris Agreement.
The Court did not treat these treaties as the entire legal universe. Instead, it considered a much wider range of international law, including customary international law, UNCLOS, environmental principles and human rights law.
This matters because international law does not operate in separate boxes. A State can have obligations under a treaty and, at the same time, obligations under customary international law.
So, what does international law require States to do?
One major takeaway is due diligence. States cannot simply say, “Our emissions are part of our national policy, so international law has nothing to say.”
The Court recognised obligations relating to preventing significant environmental harm and taking appropriate measures to address climate change.
The Paris Agreement’s 1.5°C temperature goal also becomes important in understanding States’ obligations. Nationally Determined Contributions, or NDCs, are nationally decided, but that does not mean States have unlimited freedom to choose whatever target they want.
The Court also connected climate obligations with the regulation of activities within a State’s jurisdiction, including activities by private actors.
In simple terms:
A State may not escape international responsibility merely because the actual emissions came from companies or other private actors.
What about human rights and the oceans?
This is another reason the opinion is so useful for CLAT PG.
The Court connected climate change with human rights, recognising the importance of a clean, healthy and sustainable environment for the enjoyment of human rights. That creates an interesting bridge with constitutional law, especially questions involving Article 21 and environmental protection in India.
Then there is UNCLOS.
Article 192 requires States to protect and preserve the marine environment, while Article 194 deals with preventing, reducing and controlling marine pollution. For small island States, this is particularly important because rising sea levels threaten not only land but also livelihoods, maritime zones and access to resources.
The big PIL concept: Erga omnes
If you want one phrase from this opinion to remember for an exam, remember erga omnes. An erga omnes obligation is an obligation owed to the international community as a whole.
The Court’s reasoning also engages with erga omnes partes obligations, where treaty obligations are owed collectively to the States parties. This connects directly with cases such as Barcelona Traction and Belgium v. Senegal.
The significance is simple: climate obligations are not necessarily a private matter between two States. Other States can have a legal interest in compliance with obligations owed to the international community or to the parties collectively.
What happens if a State breaches its obligations?
The Court applied the general principles of State responsibility. Possible consequences can include cessation of the wrongful conduct, guarantees of non-repetition and reparation, depending on the circumstances.
But there is an important limitation: the Court did not calculate individual States’ climate liability or decide how much compensation a particular country must pay.
Causation remains a difficult issue because climate change is cumulative and involves emissions from many States over long periods.
For a broader understanding of recent judgments relevant to your preparation, read our guide to 10 Important Judgments You Should Prepare for CLAT PG 2027.
For CLAT PG, the key is not to treat this opinion as just another current affairs topic. It is a single judgment that connects multiple areas of Public International Law, from advisory jurisdiction and treaty law to State responsibility, erga omnes obligations and human rights.
Add it to your CLAT PG 2027 judgment list, revise the key concepts, and you’ll have one important area of Public International Law covered.
If you’re preparing for CLAT PG 2027, the real value of studying judgments like the ICJ’s Climate Change Advisory Opinion lies in understanding how a single decision connects multiple areas of Public International Law.
To find the right preparation approach for you, connect with our counsellor at +91 93596 84056 or write to courses@lawctopus.com.
About the Author
Ms. Mansi Mankotia holds a B.A. LL.B. and LL.M. from HPNLU, Shimla. She secured AIR 906 in CLAT PG 2020 and is currently a Senior Learning Manager at Lawctopus Law School.