Since the 1970s, English trade unions got involved in various types of legal action aiming at equal pay, particularly by accompanying female complainants to court. Is this involvement in the fight against gender discrimination a direct consequence of member feminization and the research of a better balance between the sexes in trade unions ? Based on a mix of interviews with the main actors of this mobilization and archive documents, this article first stresses the influence of women’s strikes and feminist groups on the obtention of a legislation in 1970 and on the importance of the legal strategy of a non-governmental agency, the Equal Opportunity Commission, in the evolution and application of English law in the 1980s. This survey then focuses on the role of certain men, trade unionists of committed lawyers, who seized the anti-discriminatory law in the 1990s in order to fight the policies of reorganization led by conservative governments, and to unionize in public and private services. This legal mobilization, however, has not modified discriminatory conventional practices much, which were secured by trade union (male) negotiators. Indeed, more and more numerous at the top and at the base of trade unions, women find it difficult to make a difference in decentralized collective negotiation proceedings, faced with unwilling employers, in the context of deregulation of the English labor market.