The ICJ Climate Change Advisory Opinion and the UN Treaty Bodies: An Evolutionary Approach?

Introduction

On July 23^rd, 2025, the International Court of Justice (ICJ or the Court) issued a landmark advisory opinion (the Opinion) that underscored, inter alia, '…the protection of the environment is a precondition for the enjoyment of human rights…' (para 373). In analysing the interplay between climate change and human rights, the ICJ relied substantially on the interpretation of international human rights treaties by the United Nations Treaty Bodies (UNTB). The interaction between climate change and human rights obligations has provided a valuable opportunity to reflect on the legal character of UNTB pronouncements in determining and clarifying treaty obligations.

Interestingly, the Court had previously declared that it was not bound to interpret the provisions of international human rights treaties in strict accordance with UNTB pronouncements. Therefore, this post intends to argue that the ICJ has adopted an evolutionary approach that adapts UNTB pronouncements within the broader principles of treaty interpretation.

The Legal Value of the UNTB Pronouncements before the Opinion

As affirmed by the Court in both Diallo and Qatar v UAE, UNTB pronouncements shall be taken into account when interpreting international human rights treaties. However, these cases involve different contexts regarding the significance and role of UNTB pronouncements for the purpose of treaty interpretation.

In Diallo, the Court held that such pronouncements should be accorded ‘great weight’ (para 66) when interpreting provisions of international human rights treaties, given the supervisory role of the UNTB. However, it was not until the Qatar v UAE judgement that the Court explicitly stated that it ‘carefully considered the position taken by the CERD Committee’ (para 101).

In the case of Qatar v UAE, the Court implicitly acknowledged the pronouncements of the UNTB within the customary rules of treaty interpretation (paras 75, 101). Nonetheless, scholarly commentary suggests that the Court regarded such pronouncements as supplementary means under Article 32 of the Vienna Convention on the Law of Treaties (VCLT), thereby constraining the discretion of the interpreter to rely upon them (ILC Third Report on Subsidiary Means for the Determination of Rules of International Law, para 392).

How did the ICJ Refer to the UNTB Pronouncements in the Opinion?

The Court relied on the UNTB pronouncements to address the link between the adverse effects of climate change and human rights. Specifically, the human rights the Court referred to are the following: the right to life (paras 377-378), the right to health (para 379), the right to privacy, family and home (para 381) and the rights of women, children and indigenous peoples (para 382). In that regard, as noted by Judge Charlesworth’s Separate Opinion (para 11), the link referred to above must be consistent with international human rights law. As such, the Separate Opinion appears to deepen the analysis carried out in the Opinion, complementing the reference to the UNTB pronouncements to establish the material nexus between the adverse effects of climate change and human rights. To that end, the Separate Opinion refers to the interpretation carried out on the aforementioned rights found in equivalent human rights treaties (i.e. ECHR, IACHR), thereby confirming an existing trend in the application of human rights law to climate change-related cases.

A New Approach to the UNTB Pronouncements by the ICJ?

In the Opinion, the Court held that the enjoyment of human rights was hindered or impaired by the negative effects of climate change (para 386). The Court did not conduct an independent interpretation of the substance of each human right, nor did it evaluate how such an interpretation might support the conclusion that a connection exists between climate change and the harm inflicted upon the exercise of human rights.

Instead, the Court adopted a two-pronged approach: (1) listing certain human rights that may be impaired by adverse effects of climate change (para 376), and (2) establishing, in line with the UNTB’s interpretation, how the adverse effects of climate change hinder the realisation of these rights (paras 377-384). In the second step, the Court cited the UNTB pronouncements in its reasoning, thus appearing to recognise the authoritative value of these pronouncements on the relationship between specific human rights under international human rights treaties and the negative effects of climate change. Accordingly, the Opinion adopted an integrative approach to UNTB pronouncements when interpreting the obligations under international human rights treaties. There are two examples of this new approach:

1. The Court referred to Article 6 of the ICCPR and its relationship with the adverse effects of climate change. Specifically, it considered the legal implications that may arise vis-à-vis a State that intends to return a national who was displaced from its country of origin due to climate change-induced impacts. The Opinion (para 378) appears to have adopted the interpretation suggested by the HRC in the Teitiota v New Zealand decision (para 9.11) as its own. Rather than declaring that the HRC confirmed its interpretation of Article 6, the Court opted to refer to the decision in toto. Consequently, the Court clarified how the impacts of climate change may trigger non-refoulement obligations under Article 6 of the ICCPR vis-à-vis receiving States when climate change-induced effects in the country of origin could endanger the life of the displaced individual.
2. The Court referred to Article 17 of the ICCPR in the context of climate change. Likewise, it appears to have deferred to (para 381) the interpretation adopted by the HRC in the Billy and others v Australia decision (paras 8.9-8.12). Specifically, the Opinion in this case refers to the comprehensive assessment made by the HRC regarding the scope of positive obligations imposed on a State concerning adverse effects of climate change, with emphasis on how these obligations operate in the case of highly dependent communities to natural resources that are severely impacted by the adverse effects of climate change. To that end, the Court appears to accept HRC’s analysis as authoritative, as suggested by McMenamin (p 221), where a violation of Article 17 may occur if the State fails to implement adequate adaptation measures to address the specific climate change-induced impacts affecting the victim.

In the examples above, the expression 'In the view of the Court' is used in the Opinion, with direct reference to the UNTB pronouncements, outlining why it considers that, under international law, there is a connection between the scope of a provision of an international human rights treaty and adverse effects of climate change. The Court did not formulate its own interpretation of Articles 6 and 17 of the ICCPR. Therefore, it heavily relied on the UNTB pronouncements in analysing certain human rights and their interplay with the adverse effects of climate change.

UNTB Pronouncements and Article 31 of the VCLT

The foregoing shift can best be understood through the interpretative framework of the VCLT, in particular Article 31(3)(c). The language of the Opinion demonstrates how, when interpreting international human rights treaties, the UNTB pronouncements’ authoritative value may fall into Article 31(3)(c) of the VCLT as per the principle of systemic integration, as noted by Azaria (p 45). Although the Court has never declared expressly which rule in the VCLT permits recourse to the UNTB pronouncements (ILC Draft conclusions on subsequent agreements and subsequent practice in relation to the interpretation of treaties, with commentaries, p 115, para 24), the Diallo judgement (para 66) can assist in ascertaining this legal qualification. The judgement outlines two relevant factors: (1) the source of the mandate of the UNTB, as noted by Azaria (p 43), and (2) the objective of ensuring legal consistency in international law, following McMenamin (p 219).

UNTBs are empowered to consider individual complaints regarding violations of international human rights treaties, thereby interpreting the rights protected therein and its application to specific circumstances. For that reason, as pointed out by the ILC Draft conclusions, the interpretation of an international human rights treaty provision must be consistent with or consider the foregoing pronouncements to prevent contradictory interpretations of the conduct that must comply with the foregoing treaties (ILC, p 115, para 24). The importance of which unfolds when the interpretation postulated by UNTB pronouncements contributes to enlightening the open or evolving nature of the content of human rights under international human rights treaties (ILC Conclusions of the Work of the Study Group on the Fragmentation of International Law, para 251(d)(23)).

On this point, as postulated by Feria-Tinta (pp 32-33), it is a relevant factor that the interpretation also considers the normative environment that surrounds an international human rights treaty when the claim consists of human rights violations due to climate change-induced impacts. As such, the implementation of Article 31(3)(c) VCLT would entail interpreting a provision of an international human rights treaty in a way consistent with other relevant obligations binding upon the States found in climate change treaties.

Such an approach, according to Venzke (p 368), would demonstrate how the Court appears to refer to the UNTB pronouncements, although not legally binding per se, in light of the semantic authority deriving from the mandate conferred by States on the UNTB to supervise the application of international human rights treaties. This is an approach that appears to be inspired by Diallo. Further, that proposition accommodates to the fact that UNTB were the first authorities to examine the interplay that exists between human rights and the adverse effects of climate change. Consequently, it can be argued, according to Von Bogdandy & Venzke (p 7), that the ICJ made such deference to stabilise a normative expectation. That expectation rests on the consistency with the legal analysis made by UNTB regarding the impact of adverse climate change on certain human rights.

In the context of the Opinion, the value of the UNTB pronouncements may fall under Article 31(3)(c) VCLT insofar as it has contributed directly to the Court’s work in ‘… elucidating the relevant rules of international law’ (ILC Third Report, para 420). Therefore, in the view of the Court, the Opinion appears to show a shift from its original approach of treating the UNTB pronouncements as supplementary means to interpret international human rights treaties (Article 32 of the VCLT), to viewing them as having a more decisive role in the construction of treaty obligations (Article 31 of the VCLT).

Conclusion

The Opinion signals a shift from the Court’s position in Qatar, by recognising the UNTB pronouncements as authoritative sources that inform treaty interpretation under Article 31 of the VCLT. The Court’s approach in this Opinion appears to affirm the importance of these pronouncements as a general rule for interpreting the meaning and scope of international human rights treaties.

Diego Ernesto Sanchez Borjas is a PhD Candidate in Public International Law at Universitat Pompeu Fabra and a lawyer at the Barcelona Bar Association. He holds a Bachelor of Law (Hons) from Universitat Abat Oliba CEU, a Master’s in Law from Universitat Pompeu Fabra and a PGDip on EU Environmental Law from the Universitat de Barcelona.