The securitization of immigration has led to increased reliance on border enforcement, detention, and deportation to control unauthorized movements. Based on a case study of the ways that Salvadoran immigrants to the United States have experienced these tactics, this paper analyzes the spatial implications of current enforcement strategies. As movement across borders becomes more difficult for the unauthorized, national territories become zones of confinement. This carceral quality is a dimension of national territory in that undocumented and temporarily authorized migrants cannot exit their countries of residence without losing territorially-conferred rights, while if they are deported, their countries of origin become extensions of the detention centers they occupied before exit. This transformation of national spaces is accompanied by internal differentiation, as interior enforcement confines migrants to subnational spaces where they must remain to avoid detection or harassment. Securitization thus entails both extraterritoriality, that is the extension of U.S. legal regimes into foreign territories, and intraterritoriality, or the operation of different legal regimes within national territories. The paper also highlights the ways that securitization contributes to multidimensionality, such that spatial locations are rendered ambiguous, both inside and outside at the same time. Finally, the paper considers how these spatial transformations redefine citizenship and belonging.