On 21 May 2026, the International Court of Justice gave its advisory opinion on the Right to Strike under ILO Convention No. 87. By ten votes to four, the Court concluded that the right to strike of workers and their organisations is protected under ILO Convention No. 87 – one of the ILO’s eight “fundamental” Conventions.
As a matter of substance, the question before the Court was specific and binary. The existence of the right to strike, both within the ILO system and outside it, has already been the subject of discussion. While the Court’s reasoning, in particular on the rules of treaty interpretation, merits separate treatment, this post addresses the potentially unique nature and effect of the advisory opinion, given that it was rendered pursuant to the jurisdiction conferred on the Court by Article 37(1) of the ILO Constitution.
On 24 October 2023, the International Organisation of Employers (IOE) submitted comments to the ILO Director General. The IOE opposed referring the question regarding the right to strike to the Court. The basis for their opposition was that a request for an advisory opinion made pursuant to Article 37(1) of the ILO Constitution would not resolve the dispute between the ILO’s tripartite constituents as there exists “uncertainty regarding a binding effect of ICJ advisory opinions for the ILO and its constituents”.
Thereafter, in November 2023, during the discussions in the Committee of the Whole at the 349th bis (Special) Session of the Governing Body, the Employers’ group took this position further. The Vice-Chairperson of the Employers’ group stated that her group would not accept any advisory opinion from the Court, irrespective of its content. This position was based on the Employers’ view that advisory opinions “were inherently not binding”. Although the IOE did not repeat these submissions before the Court, its position on the effect of advisory opinions was supported by Australia (Verbatim Record, p. 30).
On the face of it, the position appears uncontroversial – the Court’s advisory opinions are, as a general matter, non-binding. Advisory opinions do not constitute “decision[s]” within the meaning of Article 94(1) of the UN Charter and Article 59 of the Court’s Statute. Indeed, because opinions are not binding, the consent of interested States does not affect the Court’s jurisdiction to render an advisory opinion (see, Interpretation of Peace Treaties, p. 71).
However, in relation to the proceedings regarding the right to strike, the position of the Employers’ group was simplistic. The Governing Body requested the Court to render an opinion “in accordance with Article 37, paragraph 1, of the Constitution of the International Labour Organi[z]ation”. Article 37(1) of the ILO Constitution provides that the questions “shall be referred for decision” to the Court (emphasis added). Therefore, in the words of Roberto Ago, the provision is designed to “pursue a more ambitious aim”, that is, to confer “binding force” to an advisory opinion.
Although it appears incongruous, the ILO Constitution is not alone in purporting to confer such an additional effect on the advisory opinions of the Court. Among others, similar provisions appear in the Convention on the Privileges and Immunities of the UN (Article VIII, Section 30); the Vienna Convention on the Law of Treaties 1986 (Article 66(2)); and the UN Convention against the Illicit Traffic in Narcotic Drugs and Psychotropic Substances (Article 32(3)).
The attribution of binding effects to advisory opinions has historically been the subject of informed doctrinal criticism. As far back as 1980, Guillaume Bacot criticised the propriety of such treaty provisions as they were, in his view, inconsistent with the advisory jurisdiction of the Court, which can only lead to a finding without binding effect. Similarly, Robert Kolb has noted that others have considered such provisions to amount to “legal heresy”, being an abuse of Article 34(1) of the Statute, which confines the access to the Court’s contentious jurisdiction to only States.
Such provisions have principally come to the Court’s attention in the context of review procedures in the statutes of the administrative tribunals of the ILO and the UN, both of which have now been amended to abolish a reference to the Court for a “binding” advisory opinion. In these cases, the Court was careful not to provide a definitive pronouncement on whether such provisions comply with its Statute or if the binding effect of a “decision” could be attributed to an advisory opinion. Nevertheless, the Court concluded such provisions did not bar its ability to render advisory opinions.
The first instance of the Court addressing such provisions was in 1956, in the case concerning Judgments of the Administrative Tribunal of the ILO upon Complaints Made against UNESCO. The proceedings were commenced pursuant to the erstwhile Article XII of the Statute of the ILO’s Administrative Tribunal (ILOAT), which, in the relevant part, provides that the advisory opinion given by the Court “shall be binding”. The Court noted that such effect “goes beyond the scope attributed by the Charter and by the Statute of the Court to an Advisory Opinion”. Nevertheless, the Court was of the view that as the provision does not affect its own functions and procedures, “the fact that the Opinion of the Court is accepted as binding provides no reason why the Request for an Opinion should not be complied with” (at p. 84). These views were reiterated by the Court in 2012, while rendering its final advisory opinion pursuant to Article XII of the ILOAT Statute (at para. 28).
Similar to the Statute of the ILOAT, Article 11(3) of the Statute of the UN Administrative Tribunal also provided that the Court’s advisory opinions rendered pursuant to its review procedure will be given conclusive effect by the UN Secretary-General. The Court addressed this provision for the first time in 1973 in the Application for Review of Judgment No. 158. The Court confirmed that the fact that the opinion given by the Court will have “conclusive effect…does not constitute any obstacle to the Court’s replying to the request for an opinion”. Pertinently, while the Court reiterated that such an effect is beyond the scope attributed to advisory opinions by its Statute, “[i]t results not from the advisory opinion itself but from a provision of an autonomous instrument having the force of law” (at para. 39).
Accordingly, it must be right that while advisory opinions lack binding effect in general, they can be made binding through a treaty provision. In such cases, the binding effect does not derive from the UN Charter or the Statute of the Court but as a “collateral act” contractually agreed between the parties to a treaty.
From the earliest days of the Court’s advisory jurisprudence, it has been clear that there is a distinction between the role played by the Court while exercising advisory jurisdiction, and “the particular effects that parties to an existing dispute may wish to attribute, in their mutual relations, to an advisory opinion of the Court” (Interpretation of Peace Treaties, p. 71). Even the Court’s website recognises that the requesting organs remain “free to decide, as [they see] fit, what effect to give to these opinions”.
As Kolb notes, the attribution of binding effect to advisory opinions is not contrary to the Court’s Statute or Rules. While parties cannot derogate from those texts to reduce their obligations, there is no reason why they should not be entitled to add to their obligations provided that doing so does not conflict with the letter and spirit of the texts. No such conflict exists in the case of treaty provisions providing binding effect to opinions.
These principles apply a fortiori in the context of the ILO. The ILO’s unique tripartite structure includes Governments, Workers and Employers. Yet, unlike the ILO and its member States, Workers’ and Employers’ groups lack international legal personality. Article 37(1) of the ILO Constitution provides a dispute resolution mechanism, among other things, to resolve disputes between these tripartite constituents. If it were correct that despite the express reference to a “decision” in the provision, the advisory opinion of the Court would not be binding, the provision would be left meaningless. Unsurprisingly, for this reason, the ILO noted prior to the proceedings relating to the right to strike that the binding nature of the Court’s advisory opinions has been accepted for over a century by all tripartite constituents.
In the proceedings relating to the Right to Strike, the Court was presented with an opportunity to clarify that its opinion puts an end to a long-standing dispute between the ILO’s tripartite constituents. Despite submissions made by Somalia, Indonesia and Norway urging the Court to conclude that its opinion would have binding effect, the Court did not address this issue. Instead, it confined itself to noting, in the context of its discretion, that in submitting the question to it the Governing Body “has made use of one of the options provided for in the constituent instrument of the Organization” (Opinion, para. 36).
And so, the Court has left the textual command of Article 37(1) of the ILO Constitution and the century-long acceptance of the binding nature of decisions issued under it, for another day. Whether the Employers’ group will take this silence to maintain its pre-announced refusal to accept the opinion remains to be seen.