No, holds the European Court of Human Rights, unanimously, in RMT v UK, but with differing reasons.
The case arose after the RMT abandoned secondary action at a rail contractor, Jarvis Rail Ltd, to protect members who had transferred from Jarvis to Hydrex Ltd, and ultimately agreed to new terms with Hydrex.
The unanimous decision of the Court was that there was no breach of Article 11 of the Convention, which guarantees the right to freedom of peaceful assembly and of association with others, by the UK laws restricting secondary industrial action.
The majority considered the Vienna Convention on the Interpretation of Treaties, interpreting the Convention in harmony with general principles of international law (para. 76), noting that secondary action was recognised and protected as part of trade union freedom under the International Labour Organisation Convention (ILO) no. 87 and the European Social Charter.
The majority noted that there was a broad margin of appreciation available to national legislatures in dealing with 'a secondary or accessory aspect of trade union activity" (para. 87) and "it cannot be said that the ban on secondary action struck at the very substance of the applicant's (RMT's) freedom of association" (para. 88). Overall, UK law struck a fair balance (para. 103). There was no unjustified interference with the RMT's right to freedom of association, and it was able, despite UK law, to exercise the essential elements of freedom of association in negotiating with the employer of its members and in organising a strike.
The majority of the ECHR did note that it had no competence to assess whether or not UK law complied with the ILO's charter or the European Social Charter.
There were two minority concurring judgments, with three judges jointly noting that secondary strikes were not necessarily or directly relevant to the rights or interests of those engaged in strike action, and one judge holding that Article 11 of the ECHR was not applicable to the case.
The ECHR threw out as inadmissible a challenge by the RMT to the UK's provisions on strike ballot notice provisions, noting that the RMT had complied with the UK's requirements and led a successful strike despite the procedural requirements of UK law. Readers may recall the Metrobus case.