Opinion ICJ ruling signals a new era of climate justice

The ICJ’s advisory opinion is the result of years of advocacy led by visionary law students from Pacific Island nations who refused to let their futures sink in political inaction. In 2019, they convinced their governments to pursue an ICJ opinion on climate obligations. Vanuatu — a small, low-lying Pacific nation literally fighting for survival against rising seas — elevated their campaign globally, ultimately rallying 132 countries behind a historic UN General Assembly resolution. Adopted unanimously on 29 March 2023, it called on the ICJ to clarify states’ legal duties in addressing the climate crisis.

The ICJ held public hearings from December 2 to 13, 2024 in The Hague, drawing unprecedented global engagement. By the March deadline 22, it had received 91 written statements — the most in its advisory history — along with 62 written comments and oral submissions from 96 states and 11 international organisations. Parallel to the proceedings, youth campaigners from the Pacific and beyond led powerful mobilisations, amplifying the voices of those most impacted and calling for urgent climate justice.

During the hearings, major polluters like the US, UK, Germany, and Russia sought to deflect responsibility — downplaying obligations, exaggerating complexities, and sidestepping their historical emissions. In contrast, small island states and other climate-vulnerable nations from the Global South invoked the principle of common but differentiated responsibilities and respective capabilities (CBDR-RC), arguing that developed countries — having contributed most to the climate crisis—must bear a greater share of the burden in mitigation and finance.

Acknowledging that rising temperatures are melting ice sheets and raising sea levels, the ICJ unanimously affirmed that states must “take all necessary measures” to prevent significant climate harm under international law. Crucially, it found that existing treaties — including the UN Charter and human rights covenants — implicitly require climate action, cutting off common excuses from laggard states. The Court also ruled that the Kyoto Protocol’s emission targets (1997–2020) remain legally relevant despite the Paris Agreement, empowering vulnerable nations with new tools for litigation. States may now seek compensation for pre-2020 harms, anchoring a 30-year continuum of responsibility — from Kyoto to Paris to the present.

The ICJ held that the duty to prevent environmental harm — first articulated in its Nuclear Weapons opinion — extends beyond direct cross-border damage to encompass global threats like climate change. This duty requires “stringent” due diligence and “heightened vigilance”, tailored to each state’s context and the scale of risk. In the face of escalating climate dangers, the obligation intensifies: it is not enough to adopt laws — states must enforce them rigorously and consistently.

The ICJ reaffirmed the principle of “common but differentiated responsibilities”, recognising that climate obligations must reflect historical emissions and present capacities. While it did not create new legal duties, this principle offers a vital lens for interpreting existing law. Crucially, the Court stressed that uncertainty cannot justify delaying urgent climate action.

Though the ICJ did not impose penalties, it made clear that breaches of climate obligations carry serious legal consequences — from halting harmful practices and ensuring non-repetition to mandatory emission cuts and reparations. Failure to meet Paris commitments or regulate emissions now constitutes an “internationally wrongful act”, even if the damage is not immediately visible.

The ICJ’s ruling signals a new era of climate justice, placing the prospect of climate reparations firmly on the horizon. While measuring damages remains complex, the decision opens legal pathways — from ecological restoration and financial compensation to court-ordered emission cuts and climate restitution funds. States may also seek symbolic remedies, such as mandatory apologies or compelling fossil fuel companies to fund public climate education. The framework redefines accountability, merging legal, financial, and moral dimensions of redress.

Alongside recent advisory opinions from the Inter-American Court of Human Rights (July 3, 2025) and the International Tribunal for the Law of the Sea (May 21, 2024), the ICJ’s opinion marks a pivotal moment in defining states’ climate obligations under international law. Though non-binding, these rulings are far from symbolic — they could shift the legal landscape from voluntary pledges to enforceable duties. They offer vulnerable nations a framework to demand accountability and provide climate advocates with fresh legal tools. These are not mere legal texts; they are signals of hope for climate justice.

Yet key questions remain. Will major emitters respect these obligations, or continue to hide behind legal ambiguity? Can small and vulnerable states marshal the resources to pursue claims against powerful polluters? The opinion arms the climate justice movement with strong legal arguments, but their impact now depends on political will, judicial creativity, and global pressure. The ICJ has shown the world a legal mirror; it is up to states to decide whether to act on the truth it reflects — that climate action is no longer discretionary, but a duty.

The writer teaches International Law at Aligarh Muslim University and heads its Strategic and Security Studies Programme