THE INTERNATIONAL COURT OF JUSTICE (‘ICJ’) rendered its advisory opinion on Right to Strike under ILO Convention No. 87 on May 21, 2026. The Court, by ten votes to four, observed that “the right to strike of workers and their organisations is protected under the Freedom of Association and Protection of the Right to Organise Convention, 1948 (No. 87).” Legally, the opinion augments the right to strike to the status of a human right and customary international law. In a developing State like India, the opinion can have far-reaching implications, with the Courts often referring to international labour standards.
The ICJ’s Right to Strike advisory opinion has transformed an implicit right into a core labour right under Convention No. 87, and also enhances the leverage of the labour unions. As academics Justina Uriburu and Julian Arato put it, “the opinion is arrived at the moment when the right-wing government have made attempts to erode labour rights.” It also fuels tension between international and domestic norms, where the right to strike is legal but regulated.
The opinion brought to the forefront crucial pressure points in international law by redefining the notion of consent in advisory opinions. By using the tool of treaty interpretation, the ICJ transcended State consent to such a high status that several judges had to contradict the majority view. This was apparent from the two declarations, four separate and dissenting opinions that were rendered in this judgment.
The ICJ applied the ‘relevant rules of international law’ to elevate the right to strike as part of freedom of association. However, the Court failed to clearly justify the binding nature of ‘relevant rules of international law'. Therefore, Judges regarded it as being detrimental to State consent and contradicting subsequent practice under Article 31(3)(b) of the Vienna Convention on Law of Treaties, 1969 (‘VCLT’).
This essay attempts to defend the Court's application of ‘relevant rules of international law’ under Article 31(3) (c) of the VCLT. I conclude that ‘relevant rules of international law’ has the potential to unite international law as a unified system in response to fragmentation.
As academics Justina Uriburu and Julian Arato put it, “the opinion is arrived at the moment when the right-wing government have made attempts to erode labour rights.”
The ICJ’s reasoning
The International Labour Organisation (‘ILO’), a specialised agency of the United Nations, is authorised to request an Advisory Opinion. This request came from the ILO's governing body due to divergent views between the Employers’ group and the Workers’ group, which led to the institutional crisis at the 101st session of the ILO Conference in 2012. The ICJ was requested to determine whether the right to strike is an integral part of the ILO Convention 87. In November 2023, the ILO officially requested the ICJ to render an advisory opinion on the Right to Strike. Since its creation in 1945, this was the first time the ILO made a request to the ICJ. The ILO exercised its discretion to render an advisory opinion, as there was no compelling reason to prevent the Court from doing so.
The ICJ went beyond the organisation's relevant rules and travaux préparatoires; it applied Articles 31 and 32 of the VCLT to reach its conclusion. The ICJ expansively applied the literal interpretation, i.e, despite the absence of explicit reference to the right to strike, the Court relied on the context, object and purpose of Articles 2, 3 and 10 of the ILO Convention 87 to interpret the terms ‘activities’ and ‘organisation’ to include the right to strike.
Technically, the Court engaged in activism to expand workers' social welfare by resorting to effective interpretation (effect utile) (for more on this, read here). This approach aligns with the position of the Court in the Wall Advisory Opinion (2004). In that case, the ICJ interpreted the ordinary meaning of Article 2 of the Fourth Geneva Convention to reject Israel’s contention that the Convention did not apply because the territory was not the sovereign territory of another high contracting party. Instead of reading the phrase ‘occupation of the territory of a High Contracting Party’ narrowly, the ICJ took into cognizance context, object and purpose to interpret the Convention as intending to protect civilians in occupied territory, regardless of the status of the occupied territory.
With respect to the ‘relevant rules of international law’, the Court, in the Right to Strike opinion, took cognisance of two 1966 Covenants – the International Covenant on Economic, Social and Cultural Rights (‘ICESCR’) and the International Covenant on Civil and Political Rights (‘ICCPR’), concerning the right to strike. Article 8 of the ICESCR and Article 22 of the ICCPR make explicit reference to Convention 87, along with the observations of the Human Rights Committee. As the Court stated, “because of the high degree of overlap between the States bound by the treaty under interpretation and those bound by the relevant rules of international law may indicate the existence of a common understanding of the parties regarding certain provisions of the treaty under interpretation.”
The Court also took into consideration the position of States not party to the relevant rules or States which have formulated reservations, because each of these reservations did not directly affect the rights under Convention 87 (for instance, while Kuwait has made a reservation to Article 8(1)(d), it never objected to the interpretation of the right to strike under Convention 87). Therefore, the Court concluded that the relevant rules of international law set out in the ICESCR and the ICCPR encompass the right to strike under Convention 87.
The Court concluded that the relevant rules of international law set out in the ICESCR and the ICCPR encompass the right to strike under Convention 87.
‘Relevant Rules of International Law’: A tool for all seasons
The phenomenon of fragmentation has led to a specialised regime and the possibility of States circumventing international legal obligations through forum shopping. ‘Relevant rules of international law’ could unite the international legal system into a single corpus, whereby every part of a treaty obligation must conform to other obligations under international law, thereby avoiding norm conflict and forum shopping.
For instance, in Loizidou (1996), the European Court of Human Rights (‘ECtHR’) interpreted the UN Security Council resolution as part of the UN Charter in the context of property confiscation (for more on this, see ‘Vienna Convention of the Law of Treaties’ (2012) edited by Oliver Dörr and Kirsten Schmalenbach). Similarly, in the Oil Platforms case (2003), the ICJ interpreted customary international law of self-defence. According to the legal scholars Dörr and Schmalenbach, the provision also permits the General Principle of law within its ambit.
However, several judges raised their disagreement on the broad reading of ‘relevant rules of international law’ by the Court. For instance, Judges Iwasawa and Xue regarded that as human rights are regionally limited, hence, they should not be perceived as ‘relevant rules of international law’ under Article 31(3)(c).
According to Judge Peter Tomka, the human rights instrument is not premised on all parties to the Convention; therefore, it is, in essence, a circumvention of consent, an argument echoed in the opinions of Judges Nolte and Bhandari.
In Defence of the Court’s Interpretative Approach
The Court’s approach to the ‘relevant rules of international law’ requires analysis of the nature of the instrument being interpreted, State consent vis-à-vis customary international law, and the phenomenon of fragmentation.
Firstly, the human rights and labour law regimes share a common purpose of protecting individuals' rights, which aligns with Prof. Theodor Meron's view of the humanisation of international law. Scholars have advanced the pro homine approach to treaty interpretation across both regimes; the method prioritises the most beneficial interests of individuals. The clearest articulation of the relationship between the two regimes is provided by a joint statement issued by the ILO’s CEACR (the ‘Committee of Experts on the Application of Conventions and Recommendations’) and the chairs of the UN Human Rights Treaty Bodies. It states:
“integrating human rights and international labour standards into economic and legal policy frameworks is critical to reducing inequalities and creating an environment conducive to more equitable and inclusive economic development.”
Additionally, the ECtHR in Enerji Yapi-Yol Sen v. Turkey (2009) recognised the right to strike as an integral part of freedom of association in the backdrop of the Turkish Government’s circular prohibiting public sector employees from participating in strikes.
According to para 3 of Article 8 of the ICESCR, “nothing in this article shall authorize States Parties to the International Labour Organisation Convention of 1948 concerning Freedom of Association and Protection of the Right to Organize to take legislative measures which would prejudice, or apply the law in such a manner as would prejudice, the guarantees provided for in that Convention.” Therefore, the savings clause for Convention 87 applies in its entirety to Article 8. According to the declaration of Cleveland, para 1 of Article 8, read with para 3, supports the application of Convention 87 to the right to strike.
The right to strike is recognised as customary international law, something that is reflected in widespread State practice and practice within regional human rights treaties. Therefore, it transcends State consent.
The major concern expressed by the Judges is whether, in the case of all parties to a treaty to be interpreted, are also parties to the other treaties “to be taken into account”. In the drafting history, ‘rules of interpretation’ were taken for granted, and nobody challenged the view that the treaty requires interpretation in the context of its normative environment.
Additionally in the Oil Platforms case, the ICJ interpreted the provision of 1955 Treaty of Amity, Economic Relations, and Consular Rights between the United States and Iran on essential security interest, the Court applied the general rules of international law on the use of force, to be capable of being successfully invoked, even in the limited context of a claim for breach of the Treaty, with respect to use of force. Interestingly, the Court, while interpreting economic treaty XX, paragraph 1(d), applied the customary international law principles of use of force and self-defence.
Second, as stated, Judges had expressed their displeasure at the stretching of the ‘relevant rules of international law’, as it contravened State consent. However, the right to strike is recognised as customary international law, something that is reflected in widespread State practice and practice within regional human rights treaties. Therefore, it transcends State consent. As Article 38 of the VCLT provides, what matters is that consent is premised on the general consent of States as a whole, and customary international law binds States that have never explicitly agreed to an obligation. Hence, consent becomes collective. Moreover, the Deputy Spokesman for the U.N. Secretary-General reiterated the U.N. view that the right to strike is indeed customary international law.
The requirements of customary international law are state practice and opinio juris. According to James J. Brudney, the right to strike fulfils these standards. He particularly contends that opinio juris is inferred from general practice determined by a national or international tribunal. In 2012, the CEACR identified 92 countries in which the right to strike is recognised as a constitutional right. Also, States that are not parties to the ILO Convention have invoked the right to strike, and the national courts of two of the six non-ratifying countries (Brazil and Kenya) have expressly invoked ILO membership and/or principles as guidance in their domestic-law decisions. Also, States by consenting to the VCLT have accepted the interpretative mechanism under the VCLT, which includes reference to ‘relevant rules of international law’ beyond the treaty framework, including customary international law. As stated in the Nicaragua case (1986), rules of international law apply independent of treaty participation.
Third, international law has become increasingly susceptible to fragmentation, leading to the dilution of international legal obligations through weaker regimes and forum shopping. Scholars like Gerhard Hafner have argued that fragmentation has benefits, including greater flexibility in issue-specific regulation and greater expertise in systematically addressing complex issues. However, it could conflate the legal obligation vis-à-vis the States, result in divergent interpretations, and cause institutional isolation due to contextless interpretation.
‘Relevant rules of international law’ seek to integrate different rules and ensure that any special regime emerging from fragmentation does not, in any way, become a legal Frankenstein. For the application of the ‘relevant rules of international law’, all members are required to be parties to the relevant rules. However, as the International Law Commission’s report on fragmentation states in the context of WTO, “This would have the ironic effect that the more the membership of a multilateral treaty, such as the agreements covered by WTO, expanded, the more those treaties would be cut off from the rest of international law”. This would also lead to the isolation of multilateral treaties, which may have been concluded as a framework agreement for interpretation.
Conclusion
The ICJ, through effective interpretation, has broadened the scope of freedom of association to include the right to strike. In doing so, it has clarified/expanded treaty interpretation. The Court’s interpretation of subsequent practice under Article 31(3) (b) by insisting on actual State practice in the context of the pronouncement of the supervisory body indicates that the pronouncement of the supervisory body backed by actual state practice would imply interpretation under Article 31(3)(b).
‘Relevant rules of international law’ under Article 31(3)(c), as this essay argues, has been liberally interpreted in line with the Oil Platform jurisprudence. However, this has come into conflict with the notion of consent, the nature of a special regime inter se, and fragmentation. Because of the analogous nature of the human rights and labour law regimes, the customary international law status of the right to strike, and the systematic integration of international human rights and labour standards into the Court’s interpretive framework, the Court’s reasoning is well-founded.