Suhana Roy is a third-year B.A. LL.B. (Hons.) student at Hidayatullah National Law University, Raipur, India

On 23 July 2025, the International Court of Justice (ICJ) issued a much-awaited advisory opinion on the duties of states to cut back anthropogenic greenhouse gases and the legal implications of not doing so. This is the situation, with a 2023 resolution of the UN General Assembly promoted by Vanuatu and a youth coalition, which has been described as a potential “constitutional moment” in international law.

The opinion is significant on two fronts. First, it affirms and reinterprets the foundational principles of the United Nations Framework Convention on Climate Change (UNFCCC), including Common But Differentiated Responsibilities and Respective Capabilities (CBDR-RC). Second, it gestures toward a deeper shift: positioning climate change not merely as a treaty-bound issue but as an erga omnes obligation rooted in human rights, equity, and intergenerational justice.

This dual move signals a transition from Paris to The Hague: from a political vocabulary of voluntary ambition to a legal grammar of enforceable duties. However, as this blog contends, although the ICJ unifies Global South standpoints and complements CBDR-RC, it creates significant gaps concerning enforcement, justice, and growth: the query, then, is whether international law can replace paralyzed climate politics.

I. Reaffirming the Climate Regime: UNFCCC, Kyoto, and Paris as a Unified Whole

A striking aspect of the ICJ’s opinion is its insistence on the continuity of the UNFCCC, Kyoto Protocol, and Paris Agreement as a single legal regime. This is a direct refutation of Global North discourses that Annex-based differentiation has been replaced by the Paris Agreement, and its self-differentiated Nationally Determined Contributions (NDCs).

The Court emphasized:

  • UNFCCC’s Annex I and II obligations remain operative, meaning developed countries still bear additional duties of finance, technology transfer, and capacity-building.
  • Climate obligations flow not solely from Paris but also from Articles 4 and 11 of the UNFCCC, reinforcing developed countries’ duties to support mitigation and adaptation in the Global South.

It is a radical refutation of Northern minimalism and a confirmation of the demands of the Global South when it comes to historical responsibility. The Court went further to extend the reach of CBDR-RC to all international environmental law, and said in para 152 it “guides the interpretation of obligations under international environmental law beyond its express articulation,” potentially influencing biodiversity, desertification, and even trade-environment disputes.

This reading transforms CBDR-RC from a treaty principle into a meta-principle of international environmental law, universalizing it much like the ICJ once did with self-determination in Namibia (1971) and Western Sahara (1975).

II. CBDR-RC and the Politics of “Dynamic Differentiation”

Nevertheless, the nuance of the opinion is that it delivers a new interpretation of CBDR-RC because it recognises the qualification by Paris: obligations must be viewed “in light of national circumstances.” The Court interprets this not as dilution but as recognition that the binary of “developed” versus “developing” is not static.

China, as both a major emitter and leader in development, it threatens to divide solidarity within the Global South: major emerging economies might now be subjected to greater scrutiny even with per-capita emissions disparities.

This doctrinal shift mirrors equity debates at COP negotiations, where “national circumstances” have often been a Northern wedge to weaken fixed differentiation. The ICJ’s endorsement thus carries ambivalence: it entrenches CBDR-RC but opens room for contested reinterpretations in future litigation and negotiations.

III. Temperature Goals and Doctrinal Overreach: 1.5°C as Custom?

One of the opinion’s most controversial moves is its reinterpretation of the Paris temperature goal. Article 2.1(a) of Paris sets a “well below 2°C” target, with “efforts to limit to 1.5°C” as aspirational. The ICJ, however, treats COP26 and COP28 decisions referencing 1.5°C as evidence of “subsequent agreement” modifying Paris’s object and purpose, essentially elevating 1.5°C into a binding obligation.

It is doctrinally adventurous but dangerous. First, decisions of COP do not have a treaty-amending nature according to the Vienna Convention Article 39, which raises the issue of their legality. Second, 1.5°C is expected to be exceeded within years, so there is a paradox: has the ICJ just enshrined a duty that is already impossible to meet, which means that all states are liable to the “continuing wrong”?

This reflects what might be termed “judicial climate accelerationism”: importing politically aspirational targets into legal adjudication without reconciling feasibility or equity. It risks reinforcing IPCC-derived pathways (e.g., 43% global GHG cuts by 2030) that ignore CBDR-RC’s distributive dimensions.

IV. From No-Harm to Erga Omnes: Climate as a Duty to All Humanity

The Court draws from the no-harm principle (Trail Smelter, Pulp Mills) but extends it, framing climate harm as an “obligation erga omnes”: a duty owed to the international community as a whole. This parallels Barcelona Traction(1970) and its articulation of erga omnes for genocide and slavery.

The novelty lies in fusing environmental law with erga omnes logic, enabling any state to invoke climate breaches regardless of direct injury. This has two consequences:

  1. It could unlock climate litigation by small island states (SIDS) seeking reparations against major emitters.
  2. It embeds climate change within the “humanization of international law”, shifting it from reciprocity-based obligations to community-based duties.

Yet, the opinion leaves enforcement vague. For example, in its Advisory Opinion of 19 July 2024 on the legal consequences of Israel’s policies in the Occupied Palestinian Territories, the ICJ’s findings have thus far been ignored by the state concerned. Climate erga omnes may face a similar risk: becoming normative without coercive force, its impact felt more in shaping how domestic and regional courts interpret climate harm and liability than in compelling immediate compliance.

V. Human Rights and Intergenerational Equity: Expanding the Temporal Jurisdiction of Law

The ICJ explicitly links climate inaction to human rights violations, citing Articles 6 (life) and 12 (health) of the ICCPR, aligning with recent cases like:

  • UNHRC, Torres Strait Islanders v. Australia (2022): held inadequate adaptation violated cultural and family rights.
  • German Federal Constitutional Court, Neubauer (2021): recognized emissions constraints as necessary to protect future generations’ freedoms.

By embracing intergenerational equity, the ICJ effectively temporalizes state responsibility: obligations now extend not only horizontally (to other states) but vertically (to future persons). This reorients climate law toward fiduciary stewardship, challenging positivism’s focus on present consent and opening the door to jus cogens-like arguments for planetary protection.

VI. Enforcement and Its Limits: Conduct, Not Result

Notably, the ICJ does not create new binding enforcement mechanisms. It holds that:

  • Domestic mitigation is an obligation of conduct: states must act diligently but are not strictly liable for results.
  • Procedural duties (e.g., NDC submissions) carry stronger enforceability.

This shows consistency with Paris and its idea of pledge and review, which is agitating to increase the judicial bite. The legal pronouncements, as Judge Xue Hanqin wrote in her separate opinion, can become empty without the existence of a favorable international economic order, which consists of finance, technology transfer, and carbon space. 

The Global South finds this disparity particularly striking: the opinion upholds CBDR-RC, yet avoids the subject of finance conditionalities, pushing developing countries between the obligations of mitigation and deficiencies of means of implementation.

VII. Litigation Potential: National and Regional Uptake

Despite weak enforcement, the opinion’s normative authority could be catalytic. Advisory opinions, though non-binding, often function as interpretive baselines—structuring argumentation in domestic and regional fora.

As it is, cases on climate in front of the European Court of Human Rights (KlimaSeniorinnen v. Switzerland, 2024) and Inter-American Court of Human Rights (pending AO on climate and human rights) are indicators of a judicial cascade. The reasoning of the ICJ is expected to support the arguments of inaction on climate as rights-violating and support defenses such as the so-called climate necessity in investment claims. 

In this way, the opinion of the ICJ functions as a form of judicial scaffolding: it is binding in no formal sense, but it supplies a doctrinal grammar of multi-level climate adjudication.

VIII. Toward a “Second Decolonization” of International Law

The most radical new thing in the opinion is its historical echo with decolonization jurisprudence. Next, the ICJ constitutionalized the principle of self-determination into the erga omnes status (Namibia, Western Sahara) and redefined law through the lens of anti-colonial justice.

Now, climate law appears poised for a similar “second decolonization”:

  • CBDR-RC parallels historical responsibility for colonial exploitation.
  • Erga omnes climate duties echo self-determination’s universalization, extending beyond bilateral consent.
  • Intergenerational equity mirrors the shift from territorial to temporal liberation, framing obligations to future humanity as legally cognizable.

This is a radical change in the direction of planetary constitutionalism where the law transforms beyond the state focused consent to the management of shared ecological commons.

IX. Conclusion: Law’s Leap, Politics’ Lag

The ICJ’s opinion neither rewrites climate law overnight nor resolves equity deadlocks. It is, instead, a juridical acceleration of stalled politics: reaffirming CBDR-RC, elevating erga omnes, and entwining human rights and intergenerational justice into the climate regime’s normative DNA.

Its transformative potential lies not in coercion but in codifying new argumentative baselines: making it harder for states, courts, and even investors to ignore that climate inaction is no longer merely policy failure it is a breach of legal order.

The deeper question now is institutional: can The Hague succeed where Paris stalled? If history is any guide, advisory opinions often prefigure shifts that politics later consolidates. Climate change, like decolonization, may thus require law to move first, politics to catch up.