Author: Dr. Bharath Palle*
The opinions and views expressed herein are the author’s alone, and do not represent the policy, position, or opinions of any institution. The author would like to express his gratitude to Dr. Kabir A.N. Duggal, C.Arb., for his invaluable comments and guidance.
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On 21 May 2026, the International Court of Justice (ICJ) issued an advisory opinion concluding that the Freedom of Association and Protection of the Right to Organise Convention, 1948 (No. 87) protects the rights of workers and trade unions to strike and engage in temporary work stopagge or slowdowns.[1] The advisory opinion was sought by the International Labour Organization (ILO), which considers Convention No. 87 as among a handful of “fundamental” conventions that sets out the “core principles which all Member States must respect.” Apart from the significance of the question involved, the Court’s advisory opinion lays down numerous important principles for interpreting treaties under the Vienna Convention on the Law of Treaties, 1969 (“VCLT”), and for assessing the relevance of subsequent state practice in understanding the context of treaties and international conventions.
FACTUAL BACKGROUND
Founded in 1919 for promoting improvements to the conditions of labour, the ILO became the first specialized agency of the United Nations in 1945. The ILO has a tripartite structure to ensure representation of workers, employers, and governments. In 2012, at the 101st Session of the International Labour Conference—the ILO’s highest decision-making body—the groups of workers and employers strongly disagreed with each other on whether the rights of workers and their organizations to strike was protected by Convention No. 87. While the workers insisted that Convention No. 87 protected workers’ right to strike, the employers denied that this Convention recognized such a right. As a result, the Labour Conference’s work in 2012 was disrupted and eventually resulted in a protracted institutional crisis for the ILO.
In November 2023, the ILO’s Governing Body—its secretariat—formally sought an advisory opinion from the ICJ on a simple question: “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 COURT’S ADVISORY OPINION
The Court unanimously resolved that it could respond to the question posed because (1) the ILO had been duly authorized by the UN Charter to request advisory opinions; (2) the advisory opinion involved a question of a legal nature; (3) the question was within the scope of the ILO’s activities.
The Court was more divided (by ten votes to four) on the substantive issue of interpreting Convention No. 87, because the treaty does not explicitly refer to a right to strike. The Court, however, brought to bear a series of important tools and approaches for interpreting the Convention that we summarize below.
VCLT rules of interpretation applies even to treaties that predate it: The Court held that Convention No. 87 must be interpreted using the well-known rules of interpretation laid down in the VCLT. Although Convention No. 87 pre-dates the VCLT by over twenty years, the Court pointed out that the principles set out in Articles 31 to 33 of the VCLT reflect the rules of customary international law that must guide treaty interpretation.
Lack of an express treaty reference to an issue not conclusive: The Court held the “absence of an express treaty provision governing a certain issue does not necessarily mean that the issue is excluded from that treaty.” Rather, that such exclusion must be inferred from the entirety of the treaty’s text as well as “context and the object and purpose of the treaty.” Because the text of Convention No. 87, its context, and its object and purpose did not all exclude a right to strike, the Court held that it would be unwarranted to conclude that the treaty did not support such a right.
Text of Convention No. 87 supported workers’ right to strike: Article 31 of the VCLT provides that the provisions of a treaty must be accorded good faith interpretation based on the treaty’s context, and in light of the treaty’s object and purpose. The Court found that Articles 2, 8, and 10 jointly supported an interpretation that Convention No. 87 protected a right to strike. Article 2 provided that workers and employers have a right to establish and join organizations of their choosing. Article 3 recognizes the rights of workers’ organizations to “organize their administration and activities and to formulate their programmes.” Finally, Article 10 defines an “organization” to refer to “any organization of workers… for furthering and defending the interests of workers…” Since a strike is an activity involving work stopagge or slowdown by workers or worker organizations, it followed that this was an “activity” protected by Article 3. The Court also deemed it significant that strikes were among the main weapons in the arsenal of workers and trade unions to promote and defend their interests as well as to improve their working conditions. Since the Convention protected workers’ freedom of association to take collective action to defend their interests, the Court concluded that “the protection of the right to strike is in line with the object and purpose of Convention No. 87.”
Subsequent state practice for an “authentic” means of interpretation versus state practice for a “supplementary” means of interpretation: The Court did not conclude its opinion with its textual analysis of Convention No. 87; instead, it looked to subsequent state practice to bolster its conclusion. Here, the Court drew an important conceptual distinction.
- Article 31 paragraph 3 (b) of the VCLT provides that a treaty must be interpreted in the context of “any subsequent practice in the application of the treaty which establishes the agreement of the parties regarding its interpretation.” If the Court discovered any subsequent state practice that evidenced a common understanding of the parties, it would “constitute[] objective evidence of the understanding of the parties as to the meaning of the treaty.”
- Article 32 of the VCLT also authorizes recourse to “supplementary” materials for interpreting a treaty including the travaux preparatoires to confirm the textual meaning of a provision or ascertain its meaning when the ordinary interpretation is “ambiguous or obscure” or “leads to a result which is manifestly absurd or unreasonable.”
- The Court held that subsequent state practice might serve as a “supplementary means” of interpreting the treaty, even if there is no common understanding among state parties.
- The Court also explicitly held that the “supplementary” materials referenced in Article 32 were not exhaustive, and that reference to other materials not explicitly identified in Article 32 was also permissible.
No common understanding among state parties regarding the right to strike: Because of conflicting positions espoused by different state parties including in their submissions to the ICJ, the Court did not find—for the purpose of Article 31 paragraph 3 (b) of the VCLT—any authentic evidence of a common understanding of the state parties to Convention No. 87 regarding the right to strike. The Court also briefly reviewed the travaux preparatoires and found them inconclusive.
Subsequent state practice as a supplementary means of interpretation: Relying on a wide number of international covenants, regional human rights treaties, and other instruments, the Court concluded that subsequent state practice among parties to Convention No. 87 bolstered its textual analysis for inferring protections for the right to strike. The Court reasoned that “a 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.”
- There was, for instance, a “high degree of overlap” among the signatories to Convention No. 87 and the parties to the International Covenant on Economic, Social and Cultural Rights and the International Covenant on Civil and Political Rights both of which contained rules of international law regarding the right to strike. The Court considered the rules of international law codified in those covenants as relevant for interpreting Convention No. 87. Even the handful of signatories to Convention No. 87 that had never joined the latter covenants had expressed their understanding that Convention No. 87 protected the right to strike.
- The Court also looked to regional legal instruments including the African Charter on Human and Peoples’ Rights, the Charter of the Organization of American States as well as the European Convention on Human Rights. All these different treaties and charters either explicitly protected workers’ right to strike or contained language—such as “supporting freedom of association and assembly”—which regional courts had interpreted to support protections for the right to strike. Because a vast number of parties to Convention No. 87 are also parties to these regional instruments, the Court considered them as “reveal[ing] a shared view” that “the protection of the right to strike is encompassed in the protection of the freedom of association.” This state practice was relevant for interpreting the scope of “the protection of the freedom of association under Convention No. 87” to include protections for the right to strike.
Interpretation of supervisory bodies tasked with implementing treaties constitutes “supplementary” material but not state practice: The ILO’s supervisory bodies had over several decades consistently interpreted Convention No. 87 to support a right to strike. The Court refused to consider this as “subsequent practice in the application of the treaty” for the purposes of Article 31 paragraph 3 (b), because such pronouncements do not establish the agreement of the state parties to the treaty. However, the Court considered such pronouncements to be relevant, when they “give rise to, or refer to, subsequent State practice” for ascertaining the meaning of a treaty provision. In addition, such pronouncements—while not binding on the Court—also have “great weight” as a supplementary means of interpreting treaties under Article 32 of the VCLT. In this case, the Court used the interpretation of the ILO’s supervisory bodies to confirm its own independent interpretation of Convention No. 87.
KEY TAKEAWAYS
We should mention two key takeaways here. Because the Court did not resolve the “precise content, scope or conditions for the exercise” of the right to strike, there are still considerable questions on how the ILO’s monitoring and implementation will shape this right. More generally, the Court has endorsed an innovative method for understanding how state practice must shape treaty interpretation. Although there were several dissenting opinions on the issue of this methodology, this novel method may well prove influential in the days to come.
*Dr. Bharath Palle practices as a commercial litigator at a law firm in New York City. He holds a doctorate in law from Harvard Law School and has previously worked as a litigator in Chennai, India.
[1] The philosopher Wesley Newcomb Hohfeld argued more than a century ago that there were four distinct types of legal rights: claims, privileges (or liberties), powers, and immunities. To reprise very briefly:
i. A has a claim against X for $500 if and only if X owes A a duty to pay $500.
A has a privilege against X to eat his sandwich if and only if X has no claim against A that A not eat his sandwich.
ii. A has the power to enter a contract with X for the sale of a widget if and only if X has a liability to having X’s legal interests concerning the widget be changed by A.
iii. Finally, A has an immunity to being called up for military service, if and only if X has a disability from calling A up for military service.
A worker’s “right to strike” is therefore best understood as a cluster-right comprising (depending on the specifics of each jurisdiction), of the privilege of withholding his labour after issuing a strike notice, the privilege of picketing the employment premises, a claim against non-interference or physical violence by the employer, etc.