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    The right to strike under ILO Convention No. 87: the curtain falls with the advisory opinion of the International Court of Justice

    Chris AnuBy No Comments22 Mins Read
    The right to strike under ILO Convention No. 87: the curtain falls with the advisory opinion of the International Court of Justice
    Post Views: 25

    Yasmine Janssens(KU Leuven, Institute for Labour Law)
    July 14, 2026

    Introduction

    On 21 May 2026 the curtain finally fell on a long-standing point of contention that had not only held the International Labour Organisation, but the entire international (labour) legal order, in its grip for years.1 The International Court of Justice pronounced itself, after years of (institutional) controversy, positively on the question whether the right to strike is contained in ILO Convention No. 87 on Freedom of Association and Protection of the Right to Organise. The advisory opinion of the International Court of Justice constitutes a turning point, but most likely not an end point to this discussion.

    From a culture of recognition to a long-standing point of contention

    In 1948, within the tripartite framework of the International Labour Organisation, ILO Convention No. 87 was negotiated. Although the right to strike was not expressly anchored in the text of the Convention,2 this did not at that time lead to fundamental controversy.3 On the contrary, within the Organisation there gradually grew a ‘culture of recognition’ whereby the right to strike was considered an intrinsic component of the freedom of association.4 From 1989 onwards, however, the Employers’ Group began to contest that anchoring of the right to strike emphatically and openly.5 The controversy culminated in 2012 during a sitting of the Committee on the Application of Standards, where the Employers’ Group stated that no legal basis for a right to strike could be found in Convention No. 87.6 According to the Employers’ Group, the right to strike cannot be considered to be encompassed by Convention No. 87, as it is neither explicitly mentioned in the Convention nor implicitly derived from its provisions.7 This position is based on a strict textual interpretation and is further supported by references to the Convention’s preparatory works, which state that the draft Convention was limited to freedom of association,and did not address the right to strike.8 In doing so, the Employers’ Group rejects the now widely recognised link between freedom of association and the right to collective action.9

    It is important to note that this controversy surrounding the right to strike is not confined solely to legal discourse but also has a geopolitical dimension. Moreover, not all ILO Member States have ratified Convention No. 87.10 Such reluctance often stems from the view that the protection of trade union freedoms, and by extension the right to strike, is difficult to reconcile with national legislation. India provides an illustrative example in this regard: the country has ratified neither Convention No. 87 nor Convention No. 98. Among the reasons cited are existing domestic provisions that significantly restrict, or even prohibit, collective action, including strikes, by civil servants and public-sector employees.11 In addition, there is another category of States that have formally accepted the relevant ILO Conventions but where the right to strike is substantially undermined in practice due to structural shortcomings within their domestic labour law systems. Yet Convention No. 87 is a fundamental ILO Convention, meaning that all ILO Member States, even in the absence of ratification, are obliged to respect, promote, and realise the fundamental rights it enshrines, in this case, freedom of association and the effective recognition of the right to collective bargaining.12 This tension between formal recognition and effective protection is also reflected in international data. In 2025, the right to strike was restricted or prohibited in 131 countries, representing 87% of the States surveyed and the highest level recorded since monitoring began. This is particularly striking given that a substantial majority of ILO Member States have ratified Convention No. 87.13Effective protection of the right to strike appears especially problematic in regions such as the Middle East, North Africa, and Asia-Pacific,14 highlighting the persistent gap between formal ratification and the actual protection of the right in practice.

    The request for an advisory opinion: a historic step in the history of the International Labour Organisation

    Against the background of these tensions, Article 37 of the ILO Constitution provides for the possibility to submit the question to the International Court of Justice.15 In the absence of a clear majority for a referral, the International Labour Organisation in 2015 presented a joint declaration that led to a so‑called “joint agreement”, albeit without resolving the question whether the right to strike is protected by ILO Convention No. 87.16 Several years later, in 2023, for the first time in the history of the Organisation, the Governing Body decided to approach the International Court of Justice with the request for an advisory opinion on the question.17 Such an opinion is formally not legally binding, but does carry an enormous legal, political and moral weight, whereby it offers an authoritative interpretation and exerts a strong influence on international law.18

    The written statements and public hearings

    In the course of 2024, States and organisations could submit written statements and comments concerning the question.19 In October 2025 the public hearings followed, whereby the positions were explained.20 A concise summary of some of the principal arguments and points of attention follows below.

    During the proceedings, divergent views emerged regarding the existence of an internationally recognized right to strike. The majority of States and organisations, including Australia, Brazil, Canada, Colombia, Germany, Egypt, France, Italy, Mauritius, Mexico, The Netherlands, Norway, Poland, Somalia, Spain, Tunisia, Uruguay, Vanuatu, United Kingdom, United States of America and South Africa, as well as the International Labour Office, the International Cooperative Alliance, the International Trade Union Confederation and the Organisation of African, Caribbean and Pacific States, took the view that the right to strike is indeed embodied in ILO Convention No. 87. By contrast, Bangladesh, Belize, Costa Rica, Japan, Panama, and Switzerland, together with Business Africa and the International Organisation of Employers, disputed that such a right could be derived from Convention No. 87. Indonesia did not adopt a clearly articulated substantive position on the issue, but instead advocated further recourse to social dialogue within the tripartite structures of the International Labour Organisation before the International Court of Justice should proceed to issue an advisory opinion on the dispute.21

    The supervisory bodies of the International Labour Organisation22 emphasise that the right to strike, although not expressly included in ILO Convention No. 87, nevertheless constitutes anintrinsic corollaryof the freedom of association protected by that Convention. The right to strike would indeed flow directly from Article 3 of the Convention,23 which determines that workers’ organisations have the right to organise their activities freely and to determine their programmes autonomously, which would also include the use of strikes.

    The workers’ side, partly represented by ITUC,24 states that ILO Convention No. 87, interpreted in accordance with the principles ofeffet utileand good faith, and read in the light of both the nature of the Convention as a statement of principle and its objective to guarantee freedom of association and improve working conditions, unambiguously shows that the right to strike constitutes an inherent component of this Convention.

    The employers’ side, partly represented by the International Organisation of Employers,25 considers that Convention No. 87 merely protects the freedom of association and the right to organise, and provides no basis for the right to strike.26 The broad interpretation by the Committee of Experts on the Application of Conventions and Recommendations has never been formally approved by the Member States. By deriving the right to strike directly from the Convention, the Committee would exceed its competence, which according to the employers’ side runs counter to the rule of law and the principle of legal certainty.

    The advisory opinion27

    On 21 May 2026 the International Court of Justice held in an advisory opinion that the right to strike is contained in ILO Convention No. 87. The Court first confirmed its jurisdiction,28 and considered that there were no “compelling reasons” present that justified a refusal to give advice.29 The Court first turns to the question how ILO Convention No. 87 must be interpreted. In doing so, it starts from the finding that, although the Vienna Convention on the Law of Treaties formally does not apply to older treaties, Articles 31 to 33 thereof do reflect generally accepted rules of customary international law, and in this case can thus be applied.30 Some parties argued that the Convention’s preparatory works (travaux préparatoires) should be accorded particular weight,31 notably because the ILO places great value on its historic tripartite negotiating process. The Court rejected this view, holding that no special interpretative rule exists that would displace the general principles of international treaty interpretation. Consequently, the preparatory works may serve only as a supplementary means of interpretation and not as a decisive source.32

    Article 31(1) of the Vienna Convention on the Law of Treaties provides that “A treaty shall be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in their context and in the light of its object and purpose.” Although ILO Convention No. 87 does not contain an explicit reference to the right to strike, this does not mean that such a right isipso factoexcluded. A combined reading of Articles 2, 3 and 10 of Convention No. 87, in accordance with Article 31(1) of the Vienna Convention on the Law of Treaties, indicates that workers’ and employers’ organizations have the right to determine their activities and programmes autonomously in defence of their interests. Since the concepts of “activities” and “programmes” are interpreted broadly, strike action may also fall within their scope. Furthermore, the Convention contains no provision excluding strikes, and the protection of the right to strike, as an essential means by which workers and their organizations defend their interests and secure improved working conditions, is consistent with the objective of ensuring the effective exercise of freedom of association. Indeed, that freedom enables workers’ organizations to engage in collective action, including through the exercise of the right to strike.33

    Article 31(3)(b) of the Vienna Convention on the Law of Treaties provides that “there shall be taken into account, together with the context … (b) any subsequent practice in the application of the treaty which establishes the agreement of the parties regarding its interpretation”. The International Court of Justice has clarified the distinction between subsequent practice as an authentic means of interpretation under Article 31(3)(b) and subsequent practice as a supplementary means of interpretation within the meaning of Article 32 of the Vienna Convention on the Law of Treaties. In the present matter, the Court undertakes a detailed examination of the jurisprudence and positions of the various supervisory bodies of the International Labour Organization, which have for decades maintained that the right to strike is implicit in ILO Convention No. 87. Although these interpretations have gradually gained broad support among a significant number of States, the Court notes that several States Parties have opposed, or at least expressed reservations regarding, such an interpretation. In the absence of consensus, the Court concludes that it cannot be established that there exists a subsequent practice demonstrating the agreement of the parties on this issue. Nor, in the Court’s view, do national legislation and judicial decisions provide sufficient evidence to establish such a common interpretation. Consequently, the Court finds that Article 31(3)(b) of the Vienna Convention on the Law of Treaties does not carry decisive interpretative weight in the present case. However, it does not exclude the possibility that such practice may still be relevant as a supplementary means of interpretation under Article 32 of the Convention.34

    Article 31(3)(c) of the Vienna Convention on the Law of Treaties provides that “there shall be taken into account, together with the context … (c) any relevant rules of international law applicable in the relations between the parties.” According to the Court, this provision does not necessarily require that all parties to the treaty being interpreted are also bound by the other relevant rules of international law in question. A rule may be regarded as “applicable in the relations between the parties” where it reflects a common understanding concerning certain provisions of the treaty under interpretation. Although there is no other international treaty rule on the right to strike that is binding on all parties to ILO Convention No. 87, both the International Covenant on Economic, Social and Cultural Rights (ICESCR), in particular Article 8(1)(d), and the International Covenant on Civil and Political Rights (ICCPR), in particular Article 22, contain relevant provisions protecting the right to strike and expressly refer to Convention No. 87. The question, therefore, is whether these rules are applicable in the relations between the parties to Convention No. 87. In this regard, it is significant that there is a very high degree of overlap between the States that are parties to Convention No. 87 and those that are parties to the ICESCR and the ICCPR. Only four States are parties to Convention No. 87 without also being parties to both United Nations Covenants. The International Court of Justice therefore concludes that the two Covenants contain relevant rules that must be taken into account in the interpretation of Convention No. 87, as they contribute to the common understanding that the right to strike is inherent in the freedom of association guaranteed by that Convention.35

    As a final step, the International Court of Justice examines whether, pursuant to Article 32 of the Vienna Convention on the Law of Treaties, “recourse may be had to supplementary means of interpretation, including the preparatory work of the treaty and the circumstances of its conclusion, in order to confirm the meaning resulting from the application of article 31, or to determine the meaning when the interpretation according to article 31: (a) leaves the meaning ambiguous or obscure; or (b) leads to a result which is manifestly absurd or unreasonable.”

    The Court emphasises the use of the term “including” in Article 32, indicating that the interpretative means listed therein do not constitute an exhaustive enumeration. This opens the possibility of taking into account, in addition to the preparatory work of ILO Convention No. 87, other relevant supplementary sources. In this context, the Court relies on several interpretative considerations. First, it takes into account the subsequent practice of the States Parties, which demonstrates that a clear majority of them consider the right to strike to fall within the protection afforded by ILO Convention No. 87. Secondly, the Court considers the views and interpretations of the supervisory bodies of the International Labour Organization, which have gradually developed a broad and consistent consensus that the right to strike is a right protected under the Convention. Finally, the Court pays particular attention to wider normative developments within regional legal frameworks, including those in Africa, the Arab region, Europe, and the Inter-American system. In the European context, the Court refers, inter alia, to the European Convention on Human Rights and the case law of the European Court of Human Rights, the European Social Charter (Revised), the Charter of Fundamental Rights of the European Union, and the jurisprudence of the Court of Justice of the European Union. A substantial number of States Parties to Convention No. 87 are also bound by these regional instruments. Collectively, these instruments reflect a common understanding that the right to strike is inherent in the protection of freedom of association.36

    Taken together, these considerations confirm and reinforce the interpretation that the International Court of Justice had already reached on the basis of the general rule of interpretation contained in Article 31, namely that the protection of freedom of association under Convention No. 87 also encompasses the right to strike. The Court specifies, however, that it does not pronounce on the precise content, scope, or conditions governing the exercise of that right, the delineation of which remains a separate question.37 This conclusion was adopted by ten votes to four, with the four dissenting judges setting out their views in separate dissenting opinions.38

    As a final step, the Court examines, in accordance with Article 32, whether there are supplementary means of interpretation. With the exception of the preparatory works of Convention No. 87, the Court takes into account the subsequent practice under States parties, the case law of the ILO supervisory bodies and several regional legal frameworks. Taken together, this confirms and reinforces the interpretation to which the International Court of Justice had already come on the basis of the general rule of Article 31, namely that the protection of the freedom of association under Convention No. 87 also includes the right to strike. The Court specifies thereby that it does not pronounce itself on the concrete content, scope or conditions for the exercise of this right, the further delineation of which remains a separate issue.39 This conclusion was adopted with ten votes to four, whereby the four dissenting judges have set out their position in separate dissenting opinions.40

    A look at the (near) future

    Although formally not binding, the advisory opinion of the International Court of Justice of 21 May 2026 constitutes an important legal turning point because it confirms that the right to strike is contained in ILO Convention No. 87, and thus restores the coherence of the international labour law order and legitimises the interpretative practice of the supervisory bodies of the International Labour Organisation. Nevertheless, this by no means signifies that the debate has been definitively settled. On the contrary, the ruling rather constitutes the beginning of a new phase in which the practical, institutional and political implications still need to crystallise.

    In the short term, the impact of the opinion will be tangible within the International Labour Organisation, with the International Labour Conference of June 2026 and the subsequent meeting of the Governing Body as important reference points. There exists the possibility that a successful International Labour Conference can be a catalyst for renewed cooperation and a certain “de‑escalation” of the conflict. However, the opposite scenario cannot be excluded. Also outside the International Labour Organisation the opinion will have an important influence, since national and regional judges may use it as an interpretative guideline.

    Belgium has ratified ILO Convention No. 87,41 whereby it is binding, although it has no direct effect in the Belgian legal order.42 Since the right to strike is not explicitly constitutionally or statutorily anchored, international and European norms play an important role in the shaping of the right to strike in case law. In case law, reference is already made to ILO Convention No. 87, but within a broader framework of still other international and European legal sources, and in a fragmentary and little consistent manner. In that context, the opinion does not signify agame changer as suchfor Belgium, but can rather strengthen the normative and interpretative weight of ILO Convention No. 87 within an already existingmultilayeredframework. Whether this will effectively lead to a more coherent and predictable case law on (the modalities of) the right to strike is, however, uncertain, or even doubtful, and will depend in part on further institutional and procedural developments within the Belgian legal order.

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