This article aims to show that Locke’s discussion of tacit consent and the right to punish aliens in the Second Treatise of Government has important bearings on the moral status of undocumented immigrants. It argues that Locke conceptualized both friendly and hostile aliens, counting the former as tacit consenters to whom host states owed rights and protection. Moreover, it highlights how his approach, unlike theorists before and after him, was one that saw individuals as capable of shaping their own relationship (...) with the host. The article also examines Locke’s discussion of the federative power of the state, which includes the power to vet aliens within the country. Seen through this Lockean lens, the article argues that the vast majority of undocumented immigrants can be understood as tacit consenters or potential citizens who should be judged by how they choose to relate to the host, and not by their country of origin. While noting that the Lockean approach is not incompatible with border control, the article also shows how it puts the onus on the host to justify the power it exercises and to engage in dialogue with undocumented immigrants about what their status should be in the country. (shrink)