A Critical Analysis of UNFCCC Obligations in the ICJ’s Climate Advisory Opinion – Indian Blog of International Law

Suraj Pratim Saikia

Introduction

The ICJ’s 2025 Advisory Opinion (AO) on the obligations of States in respect of climate change is a landmark judicial pronouncement that transforms what has often been treated as a framework of political aspiration into a concrete set of legally binding obligations. In doing so, the Court decisively clarified the legal character of the 1992 United Nations Framework Convention on Climate Change (UNFCCC), the foundational treaty of the global climate regime. Widely hailed as transformative, this AO is poised to reframe the decades-long narrative of climate negotiations. It also opens the door to treating a state’s failure to fulfil its UNFCCC commitments not merely as a lapse in political will, but as a potential breach of international law.

A Multi-Layered Legal Framework

The ICJ’s most significant contribution through this AO has been its unambiguous confirmation that the UNFCCC “commitments” are indeed legally binding obligations for all State parties. It systematically categorized these duties into three main pillars (see para 185) structuring the Convention – mitigation, adaptation and co-operation (e.g., mitigation obligations under Articles 4.1 & 4.2, adaptation under Articles 4.1 & 4.4, and co-operation encompassing financial mechanisms under Article 11, technology transfer under Article 4.5, and support for vulnerable parties under Article 4.8). 

Equally importantly, it underscored the UNFCCC’s core principle of “Common but Differentiated Responsibilities and Respective Capabilities (CBDR-RC),” affirming that developed and developing nations do not shoulder identical obligations (see para 148). In practice, this means that the UNFCCC imposes specific additional obligations on developed countries listed in Annex I. Under Article 4(2) of the Convention, Annex I parties “shall adopt” national policies to take the lead in combating climate change by limiting greenhouse gas emissions and enhancing GHG sinks. Furthermore, developed states (Annex II, a subset of Annex I) are obligated by Article 4(3) to assist developing countries with financial resources and technology transfer. The Court also affirmed (see para 202) that all parties, regardless of economic status, hold baseline obligations under Article 4(1), including preparing periodic national GHG inventories, formulating and implementing national mitigation and adaptation programs, promoting sustainable management of sinks and reservoirs, and cooperating in scientific research, education, and public awareness. 

By confirming these long-standing commitments to be binding, the ICJ has effectively transformed what were once largely political promises into enforceable legal duties. Crucially, the differentiation principle finds concrete operational expression within the UNFCCC itself, particularly in Article 4.7. This article conditions the “effective implementation” of commitments by developing country parties on the extent to which developed countries fulfil their obligations regarding financial resources and technology transfer – a point the ICJ implicitly affirmed by acknowledging the article as one of several provisions within the UNFCCC that implement the duty to co-operate within the climate change treaty framework (see para 183). 

Crucially, having firmly established these binding treaty obligations under the UNFCCC framework, the Court rejected the lex specialis argument that climate treaties form a self-contained regime displacing other rules of international law. It held that the UNFCCC and related agreements operate within and alongside the general corpus of international law. States therefore remain bound by overarching obligations, notably the customary duty to prevent significant transboundary environmental harm and the duty to cooperate, independent of their treaty-based duties. 

Likewise, the ICJ clarified that there is no incompatibility between the UNFCCC and its offspring agreements (the Kyoto Protocol and the Paris Agreement). Terming the three treaties as “mutually supportive” it made clear that the later treaties were intended to complement and give effect to the Framework Convention’s broad obligations, not to abrogate or replace them. While the Kyoto Protocol aimed at strengthening developed-country commitments by stipulating quantified emission reduction targets for Annex I parties, the Paris Agreement enhanced implementation through nationally determined contributions aimed at a shared temperature goal, built upon the UNFCCC foundation. 

The Unspoken Obligations: Fossil Fuels and Carbon Sinks

While the ICJ’s main opinion constructed a robust legal framework, several judges argued in separate opinions that the Court should have been more forceful on the primary driver of the climate crisis, i.e. fossil fuels. For instance, the joint declaration by Judges Bhandari and Cleveland declared that state obligations to protect the climate system “fully encompass activities relating to the production and licensing of, and subsidies for, fossil fuels” (see para 2). They contended it is “unimaginable” for states to meet their UNFCCC and customary law obligations without a “rapid and drastic phase-out” of fossil fuel dependency. 

Their declaration stressed that procedural environmental duties under general law, such as conducting environmental impact assessments, must account for the foreseeable “downstream” or “Scope 3” emissions (occurring from the use of sold products) resulting from the burning of exported fossil fuels. This reasoning directly implicates the business model of fossil fuel-producing States and corporations, suggesting that authorizing new extraction projects could constitute an internationally wrongful act. In a similar vein, Judge Cleveland’s declaration noted that the Court’s AO did not sufficiently emphasize the vital, parallel obligation (inherent in UNFCCC Article 4.1(d) and critical for achieving Paris Agreement goals) to protect and enhance carbon sinks like forests and oceans (see para 4).

The Unsettled Core: Climate Justice and Differentiated Responsibilities

The most profound schism on the bench emerged over the ICJ’s interpretation of CBDR-RC, the ethical and structural cornerstone of the UNFCCC. While the main opinion acknowledged CBDR-RC as a “cardinal principle,” its characterization as merely a “manifestation of the principle of equity” that “does not establish new obligations,” drew sharp critiques. Several judges viewed this framing as a dilution of climate justice and a misreading of the Convention’s architecture. Judge Yusuf condemned the Court’s “excessively formalistic approach” (see para 2) arguing it ignored the empirical reality of differentiated historical emissions underpinning the principle. For him, CBDR-RC is about remedying historical wrongs, not abstract fairness (see generally parts III and IV of his Separate Opinion). Similarly, Judge Xue contended that CBDR-RC is a “general principle directly applicable as law” (see para 3) with substantive content rooted in historical justice and foundational for cooperation under the UNFCCC, particularly reflected in Article 4.7. Judge Sebutinde echoed this, stating the opinion “downplays the importance” (see para 9) of CBDR-RC by failing to “boldly articulate” its components as integral to the treaty’s obligations.

Conclusion

The AO is undeniably transformative, and settles the debate over the UNFCCC’s legal status by confirming that its commitments are binding obligations. By linking climate inaction to potential breaches of international law, including state responsibility, the Court has converted moral and political arguments into legal entitlements. This could provide a new and potent foundation for developing States in global negotiations while empowering domestic accountability. However, such an outcome is also complicated by the profound judicial divide on CBDR-RC. 

The ICJ’s framing of CBDR-RC as a forward-looking principle of “equity” based on evolving capabilities, rather than a principle of corrective justice rooted in historical responsibility and the UNFCCC’s own structural logic (especially Article 4.7, which conditions developing-country action on developed countries’ provision of finance and technology transfer) presents a challenge to the diplomatic strategy of any developing State. Furthermore, such an interpretation could pressure rapidly developing economies like India to assume greater burdens, potentially weakening claims to a larger carbon budget share. While questions of historical responsibility, fossil fuel phase-out, and climate justice remain contested, the AO has irrevocably changed the terms of the debate, revealing deep fractures beneath the Court’s apparent unanimity on the binding nature of the UNFCCC’s core obligations.

(Suraj Pratim Saikia, an Indian lawyer with an Advanced LL.M. from Leiden University, with interests in areas of peacekeeping, peacebuilding, international organizations, and armed conflict. He serves as an Assistant Editor for the International Organizations Law Review Journal by Brill | Nijhoff.)