Workers in the garment manufacturing industry are often subjected to violations of their rights and are exposed to low wages and difficult working conditions. In response to the exposure of these violations in the media, major fashion brands and retailers subject their suppliers to labour codes of conduct. Despite these codes of conduct being largely ineffective, this comparative case study of garment manufacturers operating from Lesotho and Eswatini illustrates that such codes provide workers and trade unions with access to bargaining (...) leverage that they would otherwise not have. A framework with a synthesis of potential sources of workers’ power is developed and related to global production networks, collective mobilisation, the nature of the state, as well as national and transnational scales of organising. Based on historical case studies of the two countries, this paper illustrates how unions in the two countries followed different approaches to using this source of power in relation to other sources of power. These approaches were shaped by their contexts and strategic choices. Theoretically, it is argued that sources of workers’ power are analytically distinct, but are relational and operate best when seen as mutually reinforcing. The term ‘power resource nexus’ is used to frame this potential mutual reinforcement of sources of power. (shrink)