This article intends to justify the possibility and the need of guaranteeing social rights for migrant people in European countries. In order to do that, it analyses the Spanish case and tries to show how exploitation and discrimination of poor migrants often represents not only an unacceptable situation from a moral standpoint, but a violation of international and constitutional standards. Finally, it argues for a progressive open borders policy and for a residence citizenship based on the recognition of equal social, political and cultural rights to everyone.