ICJ and the new legal framework for climate responsibility

This article is authored by Ananya Raj Kakoti, scholar, international relations, Jawaharlal Nehru University, New Delhi.

The landmark advisory opinion of the International Court of Justice on 23 July 2025 fundamentally reshapes State obligations under international law, compelling governments worldwide to take decisive action against climate harms, including those stemming from fossil fuel expansion. Delivered in response to a request from Vanuatu and supported by 132 States and multiple UN agencies, the ruling establishes that all countries bear customary international legal duties to protect the atmosphere and oceans from greenhouse gas emissions, irrespective of treaty participation. This decision meticulously balances the sacrosanct principle of State sovereignty with binding imperatives of global due diligence, marking a pivotal moment where environmental stewardship transcends national borders.

Climate responsibility (Representational photo / Creative Commons)

The genesis of this opinion traces back to March 2023, when the Pacific Island Forum, led by climate-vulnerable Vanuatu, approached the UN General Assembly seeking clarification on obligations of the State regarding the climate crisis. Small island developing States (SIDS), facing existential threats from rising seas despite minimal emissions contributions, framed three core questions: duties to combat climate change; legal consequences of breaches; and responsibilities concerning marine ecosystems. By December 2024, public hearings featured over 100 interventions, blending scientific evidence from the IPCC with legal arguments rooted in customary law, treaties like the UNFCCC and Paris Agreement, and human rights instruments.

The unanimous ICJ pronouncement rejects narrow interpretations, affirming climate obligations as erga omnes, owed to the international community as a whole. This echoes the 1996 Nuclear Weapons advisory opinion of the court, where environmental protection emerged as a customary norm, but extends it emphatically to anthropogenic climate disruption.

At its core, the ruling mandates States to exercise due diligence in preventing significant harm to the climate system, employing all available means from policy reforms to technological innovation. Rooted in treaties such as UNCLOS (Articles 192-194 on marine environmental protection) and the stabilisation objective of UNFCCC, these duties also crystallise as customary international law applicable universally. Emissions reduction targets must align with the best available science, rejecting reliance on aspirational pledges alone.

Critically, inaction or insufficient action constitutes an internationally wrongful act under the ILC Articles on State Responsibility (2001). Consequences include immediate cessation, non-repetition guarantees, reparations via ecosystem restoration, or monetary compensation for irreversible losses like biodiversity decline. Attribution principles are clarified: Omissions by any State organ, legislatures licensing new coal plants, regulators approving oil exploration, or executives delaying transitions, engage State responsibility collectively. Even non-parties to the Paris Agreement face these obligations, dismantling excuses for historical emitters like the US or China based on per capita disparities.

This framework draws from precedents like the ITLOS 2015 advisory opinion on deep seabed mining, where due diligence precluded environmental authorisation without rigorous assessments.

The opinion weaves climate duties inextricably with human rights, affirming that failure to act violates rights to life (ICCPR Article 6), health (ICESCR Article 12), food, water, culture (ICCPR Article 27), and self-determination (ICCPR/ICESCR common Article 1). States must conduct vulnerability and impact assessments, prioritising groups like indigenous communities, women in agrarian economies, and SIDS populations facing salinisation of freshwater sources. The Vanuatu case exemplifies this: Rising seas threaten 80% of its population within 1.2 metres of coastlines, imperilling cultural heritage and territorial integrity without eroding sovereignty through external imposition.

Cooperation emerges as a cornerstone, with obligations to mobilise finance (targeting trillions annually), transfer clean technologies, and build adaptive capacity, especially from high emitters to vulnerable states. Paris commitments of India receive bolstered legitimacy here, emphasising its advocacy for common but differentiated responsibilities (CBDR) while underscoring needs for green hydrogen and resilient agriculture funding.

Sovereignty, enshrined in UN Charter Article 2(1), permits states to pursue development paths, yet the ICJ clarifies it yields to no-harm rules under the no-harm principle (Trail Smelter arbitration, 1941). Fossil fuel-dependent economies face acute pressure: new project approvals risk illegality unless proven non-contributory to tipping points like 1.5°C warming. The ruling influences downstream institutions; World Bank voting on fossil finance must now reflect these duties, potentially curtailing loans to middle-income producers.

Domestically, it emboldens litigation: plaintiffs in Australia (Warra-Warra), Colombia (Amazonas), and South Africa (Earthlife Africa) can invoke erga omnes norms for injunctive relief against emissions-intensive permits. Globally, it synchronises with the UNGA 2022 resolution and intersects with the International Tribunal for the Law of the Sea 2024 advisory opinion, forming a climate law trilogy.

This "earthquake" in jurisprudence, as termed by observers, transforms climate science into actionable law, paving pathways for reparations funds akin to the Montreal Protocol ozone trust. It anticipates accountability at climate conferences, pressuring COP30 (Brazil, 2025) to operationalise loss-and-damage mechanisms with legal teeth. Fossil laggards may pivot to just transitions, fostering jobs in renewables while mitigating stranded assets estimated at $1-4 trillion annually by 2030.

For India, the ruling validates its net-zero 2070 pledge amid developmental sovereignty, yet demands accelerated coal phase-down and NDC enhancements. As G20 chair in prior years, India can champion technology banks and south-south cooperation, positioning itself as a bridge-builder between emitters and vulnerables.

Challenges persist: Enforcement relies on diplomacy and domestic courts, with no direct ICJ jurisdiction over contentious disputes. Nonetheless, this opinion galvanises multilateralism, urging States to view climate action not as curtailment of sovereignty but its evolution in an interdependent world.

In sum, the ICJ has etched environmental due diligence into the bedrock of international law, compelling a paradigm where planetary health underpins sovereign legitimacy. Urgent, science-aligned measures now define responsible statehood.

This article is authored by Ananya Raj Kakoti, scholar, international relations, Jawaharlal Nehru University, New Delhi.