Some South African trade unions are spitting mad at the Registrar of Labour Relations who had the temerity last week to suggest the unions should abide by the January 2019 changes to South Africa's labour law. At the apparent heart of their discontent lies the obligation of union members to cast a secret vote in favour of a strike as a legal prerequisite.

What could possibly be wrong with polling workers on whether they want to strike before they go on strike, bemused bystanders might ask. Surely the trade unions are not arguing that their members should have less say in what happens in their workplace, is such an argument not repulsive to the expansion of worker rights?

In March this year, one of the main protagonists, the National Union of Metalworkers of South Africa, was on the receiving end of urgent litigation. The Labour Court had to consider whether the union could take its members out on strike without having conducted a secret ballot. The court held that the union had to amend its own constitution to allow for the compulsory ballot, as provided in the amended legislation.

Numsa argued that the Registrar of Labour Relations had not issued...