This chapter explores the empirical relationship between immigration policy, irregular immigration and vulnerability to exploitation. The crucial factor is the imperfect enforcement of immigration controls. Controls need to be enough of a threat to mould employment relationships without warding against irregular immigration altogether – a delicate balance and one that does not always increase employers’ power over their employees. Case studies on Sweden, Italy and the USA demonstrate how the effects of workplace immigration controls vary. The chapter goes on to explore why countries falling into the different types of capitalism have historically tended towards different immigration control regimes, before discussing recent convergence. Finally, the chapter ends with a brief examination of the politics behind immigration controls. It argues that the primary reason why immigration controls have ‘failed’ is that states are trying to fulfil contradictory aims. Whilst governments are under greater pressure to control irregular immigration today – an outcome that would limit, not augment, employers’ access to this pool of labour – possibilities for enforcement are also circumscribed by the political and legal battles that rage around data protection, privacy and discrimination.