Two transnational legal regimes aim to counter some of the most severe forms of labour exploitation: one centred on the Palermo Protocol supplemented to the UN Convention against Transnational Organised Crime (UNTOC) and the other on the International Labour Organisation (ILO) Conventions. This article focuses on the relationship between transnational criminal law (TCL) and transnational labour law (TLL) and their effectiveness in tackling labour exploitation. Criminalisation and labour regulation have been seen as competing ‘paradigms’ in tackling human trafficking and modern slavery. TCL has been effective in diffusing criminal law norms around the world, but the modest number of resulting prosecutions can do little tackle the huge global market in forced or severely exploited labour. TLL, with its more decentralised and pluralistic structure, offers greater hope of achieving some alleviation of labour exploitation.