International Environmental Law: Stockholm to Paris

Pollution, climate change and the loss of biodiversity cross borders, and no state can address them alone. International environmental law has grown from a single arbitral award on smoke from a smelter into a large body of treaties and principles. Indian courts have absorbed many of these principles into constitutional law. This note traces the development, the main treaties and principles, the 2025 ICJ climate opinion, and the Indian law.

1. Development

Figure 1: Milestones in international environmental law

• Trail Smelter (USA v Canada), 1938 and 1941. No state has the right to use or permit the use of its territory in such a manner as to cause injury by fumes in or to the territory of another, when the case is of serious consequence and the injury is established by clear and convincing evidence; Canada was liable for smoke damage in Washington state.
• Stockholm Conference, 1972. The UN Conference on the Human Environment adopted a Declaration whose Principle 21 affirms the sovereign right of states to exploit their resources and their responsibility not to cause damage beyond their jurisdiction; it led to the UN Environment Programme in Nairobi.
• Brundtland Report, 1987. Our Common Future defined sustainable development as development that meets the needs of the present without compromising the ability of future generations to meet their own needs.
• Rio Conference, 1992. The Earth Summit adopted the Rio Declaration, Agenda 21 and the Forest Principles, and opened the Framework Convention on Climate Change and the Convention on Biological Diversity for signature.
• Nuclear Weapons opinion, 1996. The general obligation of states to ensure that activities within their control respect the environment of other states or of areas beyond national control is part of international environmental law.

2. Principles

Figure 2: Core principles

• Precaution, Rio Principle 15. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.
• Pulp Mills on the River Uruguay (Argentina v Uruguay), 2010. An environmental impact assessment is required under general international law where an industrial activity risks significant transboundary harm, especially to a shared resource.
• Intergenerational equity. Present generations hold the environment in trust for future generations.

3. Climate Change

• UNFCCC, 1992. Aims to stabilise greenhouse gas concentrations; recognises common but differentiated responsibilities and respective capabilities.
• Kyoto Protocol, 1997. Binding emission targets for developed countries, with market mechanisms such as the Clean Development Mechanism.
• Paris Agreement, 2015. In force from 4 November 2016; aims to hold warming well below 2°C and pursue efforts to limit it to 1.5°C (Article 2); every party sets nationally determined contributions (Article 4), reviewed through a global stocktake (Article 14)
• India's commitments. India's updated NDC (2022) aims to reduce the emissions intensity of GDP by 45 per cent from 2005 levels by 2030 and to reach about 50 per cent of installed electric power capacity from non-fossil sources by 2030; it has announced a goal of net zero by 2070.
• ICJ climate advisory opinion, 23 July 2025. The Court unanimously advised that states have binding obligations under the climate treaties, customary law, human rights law and other treaties to protect the climate system, including a duty of due diligence to prevent significant harm; 1.5°C is the primary temperature goal under Paris; fossil fuel production, licensing and subsidies may amount to wrongful acts; breaches entail responsibility and reparation.

4. Other Major Treaties

• Ozone. The Vienna Convention, 1985 and the Montreal Protocol, 1987, with universal participation; the Kigali Amendment, 2016 phases down hydrofluorocarbons.
• Biodiversity. The Convention on Biological Diversity, 1992, the Cartagena Protocol on Biosafety, 2000, the Nagoya Protocol on access and benefit sharing, 2010, and the Kunming-Montreal Global Biodiversity Framework, 2022; India's Biological Diversity Act, 2002 implements the CBD.
• Species and habitats. The Ramsar Convention on wetlands, 1971, CITES on trade in endangered species, 1973, and the Convention on Migratory Species, 1979.
• Chemicals and waste. The Basel Convention on hazardous wastes, 1989, the Rotterdam Convention, 1998, the Stockholm Convention on persistent organic pollutants, 2001 and the Minamata Convention on mercury, 2013.

5. India

• Constitution and statutes. The Forty-second Amendment, 1976 added Article 48A (State shall protect and improve the environment) and Article 51A(g) (citizens' duty to protect it); Parliament enacted the Water Act, 1974, the Air Act, 1981 and the Environment (Protection) Act, 1986 to implement the Stockholm decisions under Article 253.
• National Green Tribunal Act, 2010. Section 20 directs the Tribunal to apply the principles of sustainable development, precaution and polluter pays.

Figure 3: Indian decisions adopting international principles

6. Frequently Asked Questions

Which case first stated the principle against transboundary pollution?

The Trail Smelter arbitration between the United States and Canada (1938 and 1941), which held Canada responsible for damage in the United States caused by fumes from a smelter in British Columbia.

Are the precautionary and polluter pays principles part of Indian law?

Yes. In Vellore Citizens Welfare Forum (1996), the Supreme Court held them to be part of the law of the land, as essential features of sustainable development, and the NGT Act, 2010 directs the Tribunal to apply them.

7. Related Topics

• Topic 26: International Rivers. Equitable use and no significant harm.
• Topic 29: Law of the Sea III. The ITLOS climate opinion, 2024.
• Topic 32: Antarctica and the Arctic. The Madrid Protocol.