Irregular migrants lack the formal authorisation to reside in the country in which they live; therefore, they are at risk of being detained and deported. This chapter will examine the ways in which states respond to irregular migration. It will first consider the various forms of detention and removal of irregular migrants. Return policies for irregular migrants include forced deportation and (semi) voluntary return. The chapter will also discuss push-backs as forms of ‘pre-arrival deportation’, the time that irregular migrants spend in immigrant detention, and what happens after they have been deported. It will then explore the alternative solution, namely regularisation policies, discussing regularisation programmes, like mass amnesties, and regularisation mechanisms through which irregular migrants can regularise themselves on an individual basis.