This paper examines the detention of asylum seekers in Canada and the ways in which penal and administrative mechanisms are increasingly used together in the area of immigration. We show that the “criminalization” of asylum seekers facilitates the implementation of punitive measures against asylum seekers, such as increased use of detention. A strong focus of this paper is on the use of provincial prisons to confine asylum seekers in administrative detention (one third of asylum seekers with a non-criminal status are held in penal institutions). As we show, criminal facilities carry out the same functions as camps : they contribute to the spatial, legal and social segregation of asylum seekers, marking them therefore as “unwanted” migrants.