In Chapter 10, we looked at what trade unions did: at the relationship between the union and the employer. In this chapter, we will examine the substantial body of law surrounding union membership. The law governs the relationship between the union member and the employer, and between the union member and the union itself. Although union membership has been declining since the 1970s, the issues to be discussed still affect many workers. In 2007, 28 per cent of UK workers were members of a union. Moreover, both pro- and anti-union writers acknowledge that the law on membership plays an important role in encouraging – or discouraging – unionism.

A rights theorist would give this chapter the title ‘freedom of association’. This denotes the right to form and join trade unions which features in civil and political rights instruments as well as economic and social ones. Rights theorists agree that the right is highly important, and they also agree on some aspects of its interpretation. For example, the right means that employers may not discriminate against workers on the grounds that they are members of a union, and that workers should be free to join a union if they want to. But other aspects of interpretation are much more controversial. Should employers be obliged to help unions by providing union officials with an office at the workplace? Can an individual be compelled to join a particular union? Can a union force its members to obey its instructions?