On 21 May 2026, the International Court of Justice (the “Court”) delivered its advisory opinion on the right to strike under the 1948 Convention on Freedom of Association and Protection of the Right to Organise (“Convention No. 87”). The request arose from a long-standing disagreement within the International Labour Organization (“ILO”) on whether Convention No. 87 protected the right to strike. Following unsuccessful attempts to resolve the dispute internally, in November 2023, the ILO Governing Body referred the question to the Court (pursuant to Article 37 of the ILO Constitution). In its Advisory Opinion, the Court concluded that the right to strike was protected under Convention No. 87 as interpreted in accordance with the customary rules of treaty interpretation reflected in Articles 31 and 32 of the 1969 Vienna Convention on the Law of Treaties (“VCLT”). A summary of the Court’s approach to treaty interpretation is below.
First, the Court recognised that Convention No. 87 does not expressly refer to a right to strike. At the same time, the Court recalled that the absence of an explicit provision does not necessarily exclude a matter from a treaty’s scope. The Court, therefore, had to assess whether Convention No. 87 protected the right to strike. The Court held that strike action, as a form of collective activity, fell within the ordinary meaning of “activities” in Article 3(1) of Convention No. 87, read together with Article 2. Article 2 of Convention No. 87 guarantees workers and employers the right to establish and join organisations of their own choosing, while Article 3(1) grants such organisations the right to organise their activities and formulate their programmes. The Court reasoned that, because the terms “activities” and “programmes” are framed broadly, they can encompass a wide range of actions undertaken by workers’ organisations in pursuit of their objectives, including the right to strike.
Second, the Court concluded that, while a significant majority of States had accepted or recognised the right to strike as being protected under Convention No. 87, a number of States had consistently challenged it or had expressed reservations. Therefore, the Court concluded that this practice did not amount to “subsequent agreement between the parties regarding the interpretation of the treaty” within the meaning of VCLT, Article 31(3)(b).
Third, the Court concluded that other relevant rules of international law applicable between the parties—particularly the International Covenant on Economic, Social and Cultural Rights (the “ICESCR”) and the International Covenant on Civil and Political Rights (the “ICCPR”) —supported the interpretation that freedom of association encompassed protection of the right to strike. In light of the high degree of overlap between States parties to the ICESCR, the ICCPR and Convention No. 87, the Court found that those treaties reflected a common understanding of the interpretation of Convention No. 87. As a result, those instruments could be “taken into account” as “relevant rules of international law applicable in the relations between the parties” under VCLT, Article 31(3)(c).
Fourth, and finally, the Court concluded that supplementary means of interpretation under VCLT, Article 32 confirmed the interpretation that Convention No. 87 included the right to strike. The Court recalled that practice falling short of establishing agreement among the parties as to the interpretation of a treaty under VCLT, Article 31(3)(b) may nevertheless be “taken into account” as a “supplementary means of interpretation” under VCLT Article 32 to “confirm” the interpretation under VCLT Article 31. The Court reasoned that, because VCLT, Article 32 did not provide an “exhaustive list” of supplementary means, this permitted the Court to consider additional materials (including subsequent practice, the pronouncements of supervisory bodies and relevant regional instruments, as well as jurisprudence).
The Court concluded that supplementary means of interpretation confirmed its interpretation based on the ordinary meaning of the treaty terms under VCLT, Article 31. In so doing, the Court took into account the fact that a significant majority of States parties had accepted the interpretation that Convention No. 87 protected the right to strike. Also, the views of the majority of States parties to Convention No. 87 were reflected in a 2015 statement of the “Government Group of the ILO Governing Body” (which recognised that the right to strike was linked to freedom of association and necessary for the effective protection of workers’ interests). Furthermore, the Court considered a range of regional human rights instruments and jurisprudence of regional courts and supervisory bodies. The Court observed that African, Arab, European and inter-American legal frameworks all reflected a close connection between freedom of association and the right to strike; this revealed a shared understanding among a large majority of States parties to Convention No. 87 (that the protection of the freedom of association included the protection of the right to strike).
The ICJ’s advisory opinion is available here.
The dissenting opinions of Judges Tomka, Abraham, Xue and Hmoud, respectively, are available here, here, here, and here.