A significant success: The effect of ITUC arguments on the ICJ’s recognition of the right to strike

In 2026, the International Court of Justice (ICJ) delivered an Advisory Opinion affirming that the right to strike is protected under International Labour Organization (ILO) Convention No. 87. Submissions by the International Trade Union Confederation (ITUC) clearly contributed to this landmark decision. The critical question now is how the principles established by the ICJ will shape future disputes.

By 2023, the global trade union movement felt compelled to counter attempts by the International Organisation of Employers (IOE) to undermine the right to strike. Anchored in the International Labour Organization (ILO) Convention No. 87 on Freedom of Association and Protection of the Right to Organise (C87), this entitlement is intrinsically linked to freedom of association - a connection employers sought to break. The employers’ position departed from decades of jurisprudence established by ILO supervisory bodies, including the Committee of Experts on the Application of Conventions and Recommendations (CEACR), the Committee on Freedom of Association (CFA) and Commissions of Inquiry, as well as principles applied by international and regional human rights mechanisms. Consequently, the International Trade Union Confederation (ITUC), which plays a key role representing the Workers’ Group at the ILO, argued for the decision taken by the Governing Body to request that the ILO Director-General refer the dispute to the International Court of Justice (ICJ).

On 21 May 2026, the ICJ delivered its Advisory Opinion by a ten-to-four majority of the sitting judges. As anticipated, applying Articles 31 and 32 of the 1969 Vienna Convention on the Law of Treaties (VCLT), the Court concluded that the right to strike is indeed protected under C87.

This post examines what the ITUC sought from the ICJ and whether its strategy succeeded. The key claims presented by the ITUC in its Written and Oral Statements proved successful. Those that were disregarded were largely inconsequential to the landmark outcome it secured. Looking ahead, the Advisory Opinion will carry significant weight in future litigation and trade disputes in which the ITUC and other workers’ organisations will seek to intervene.

A. The question submitted to the ICJ

After some deliberation, the ITUC took the position that the best strategy would be to ask one clear question, namely: “Is the right to strike of workers and their organizations protected under the Freedom of Association and Protection of the Right to Organise Convention, 1948 (No. 87)?” The ILO Governing Body approved referring this single question, which the ILO Director-General formally submitted to the ICJ.

The Workers’ Group had previously considered seeking explicit confirmation of the CEACR’s competence to interpret C87 as protecting the right to strike - especially after employers’ rejection of this authority triggered the 2012 International Labour Conference “walkout”. Ultimately, focusing solely on C87 was deemed sufficient - not least because the referral resolution itself recalled the 2014 tripartite agreement affirming the CEACR’s interpretative mandate. The Employers’ Group did seek to insert this second question, partly to divert the Court’s focus toward more complex questions regarding the content and scope of the right, but their arguments were rejected in the Court’s Opinion.

The outcome has been favourable to the protection of the right to strike at the ILO. To be sure, the ICJ clarified that its findings did not amount to “any determination on the precise content, scope or conditions for the exercise of that right”. Yet this aligns with the ITUC’s submission that once the core question was answered in the affirmative, “[a]ny consequential matters, including on the scope of the right to strike and limitations thereto, will be dealt with by the ILO’s long-standing and elaborate supervisory mechanisms.”

Crucially, the ICJ’s findings do not in any way diminish the authority of the CEACR or other supervisory bodies to interpret and apply C87. On the contrary, the Opinion recognized that “great weight” is to be given to their findings as “supplementary means of interpretation” under Article 32 of the VCLT. Indeed, as Judge Tomka observed in his Dissenting Opinion: “the Court appears to have implicitly answered a question that was never put to it: whether the CEACR is competent to determine that a right to strike derives from Convention No. 87.” While he objected to this outcome, the global workers’ movement is unlikely to do so.

Moreover, while the scope of protection is not addressed directly by the Court, it is evident that limitations must not be such as to defeat the purpose of Convention No. 87. As recognized in the Advisory Opinion, “strike action is one of the main activities engaged in and tools used by workers and their organizations to promote their interests and improve conditions of labour, thereby ensuring the effective exercise of the freedom of association protected under Convention No. 87.” Restricting access to the right to strike can therefore constitute an illegitimate interference with freedom of association under C87. Significantly, the Court intentionally left the assessment of such restrictions to the established competence of the ILO supervisory bodies.

B. Ordinary meaning, context and purpose

Article 31(1) of the VCLT requires interpretation of an international instrument “in good faith in accordance with the ordinary meaning to be given to the terms […] in their context and in the light of its object and purpose.” The ICJ agreed with the ITUC that the right to strike falls squarely within workers’ activities under Article 3 of C87. Similarly, the Court endorsed the ITUC’s submissions regarding object and purpose, recognizing the reference in C87’s preamble to the ILO Constitution and Declaration of Philadelphia as establishing that the instrument aims at “improving labour conditions.” The ITUC’s argument that protecting the right to strike is necessary to ensure the treaty’s effectiveness was not considered in detail. But the Court’s reference to the “effective exercise of freedom of association” suggests that it was responsive to this submission.

C. Reference to the 1966 Covenants, regional human rights instruments and findings of supervisory bodies

The Court’s Advisory Opinion accepted the view of the ITUC that the 1966 Covenants and related supervisory body findings were relevant rules under Article 31(3)(c) VCLT in demonstrating a “common understanding […] that the protection of the right to strike is encompassed in the protection of freedom of association.”

Furthermore, the Court treated regional human rights instruments and findings of their supervisory mechanisms as important “supplementary means of interpretation” under Article 32, again in line with the ITUC’s submissions regarding their relevance. The Opinion concluded that “the various regional instruments […] reveal a shared view of those States parties to Convention No. 87 that the protection of the right to strike is encompassed in the protection of the freedom of association […] supported by the relevant regional jurisprudence and pronouncements”, which “further confirms the interpretation reached by the Court" [under Article 31].

In doing so, the Court recognized the importance of consistency in international law, often termed “systemic integration”, while remaining anchored in state consent (see Judge Bhandari’s Declaration, and Climate Change Advisory Opinion). The ITUC (and other workers’ organizations) must now invoke the ICJ Advisory Opinion in international and regional human rights disputes to cement this consistency.

A. Arguments rejected which did not affect the Court’s conclusions

It should be conceded that not all of the ITUC’s arguments succeeded. The Court rejected the ITUC’s oral submissions that the 2015 tripartite agreements at the ILO constituted a “subsequent agreement” under Article 31(3)(a) VCLT. The ICJ also departed from the ITUC’s written submissions on the travaux préparatoires, finding these preparatory materials too ambiguous to be determinative. Yet these rejections did not undermine the core holding: the right to strike remains firmly protected under C87.

B. The submission that the right to strike is customary international law

The ITUC argued that the right to strike was not only protected under C87, but should also be regarded as customary international law. The Court remained silent on this point. Its only discussion of customary international law addressed the status of the VCLT’s own rules of interpretation.

Judge Cleveland, however, addressed the issue directly in her Declaration, observing: “Finally, although the Court does not examine the question, given the breadth of recognition of the right to strike in numerous overlapping international and regional instruments, as well as in bilateral and trade agreements, the constitutional protection of the right to strike in at least 97 States, and its legislative protection in more than 150 others, a compelling case can be made that protection of the right to strike is a principle of customary international law. Such a customary international norm would also constitute a relevant rule of international law in the interpretation of Convention No. 87.” In support, she cited the comprehensive study The Right to Strike in International Law led by former ITUC Legal Director Jeffrey Vogt.

C. The jurisprudence of national courts

The ITUC Written Statement referred not only to international and regional human rights bodies, but also to the findings of key national courts, such as the Supreme Court of Canada in Saskatchewan Federation of Labour and the ruling of the German Federal Labour Court that “collective bargaining without the right to strike [...] would be nothing more than collective begging” (1 AZR 822/79). Indeed, Judge Cleveland’s Declaration invoked this jurisprudence in the context of her observation that the right to strike is now customary international law. The Court, however, did not address these domestic rulings in its Advisory Opinion.

Nevertheless, national courts will remain vital battlegrounds - for instance, in disputes over Canada’s legislative re-definition of essential services. Here, the Advisory Opinion provides vital leverage for workers and their organizations. They will be able to rely on the Court’s reasoning regarding the importance of the right to strike for realizing freedom of association, as well as the “great weight” the ICJ affords to ILO supervisory findings.

D. Reference to trade agreements and practice

Finally, trade agreements and practice were not referred to in the Advisory Opinion, despite the ITUC’s submissions. As Harold Koh explained in the ITUC Oral Statement: “To take just one example, the 2018 US-Mexico-Canada Agreement (USMCA) not only requires those States to respect freedom of association ‘as stated in the ILO Declaration on Rights at Work’, but also expressly declares that ‘the right to strike is linked to the right to freedom of association, which cannot be realized without protecting the right to strike’.” A contrary finding by the ICJ that C87 did not protect the right to strike would have severely disrupted this and related trade agreements. In the end, the Court’s conclusions are not disruptive, but confirmatory.

Indeed, while the Advisory Opinion does not explicitly mention trade issues, the Court’s holding that the right to strike is protected under C87 will be directly relevant to trade conditionality in disputes over freedom of association and trade union rights. In this sense, once again, the Advisory Opinion promises to become a vital point of reference in trade and other disputes where the interests of workers and their organizations are at stake.

Ultimately, it is striking how closely the ITUC’s written and oral submissions map onto the findings of the ICJ Advisory Opinion. This marks an important victory for the trade union movement, reaffirming that the right to strike is an intrinsic corollary of freedom of association - both in C87, which had been in dispute, but also across international and regional human rights instruments.

It is now incumbent on all relevant stakeholders in the ILO and other international organizations, especially trade unions, to maximize the impact of the Opinion as a powerful source of leverage. Moving forward, emphasizing the ICJ’s purposive method of interpretation - which achieves consistency in international labour and human rights law - will be essential in subsequent policy disputes and litigation.