Building upon the scholarly discussion concerning the growing blurring of domestic and foreign policy domains and the changing spheres of competences of states both within and outside their borders, this article focuses on inter-state cooperation in the field of migration and international relations. I attempt to answer two interrelated questions: how does collaboration on migration affect the bargaining dynamics between migrant-sending and migrant-receiving countries? And specifically, how does the contested process of externalisation of border control practices to third countries influence power relations between the two? Particular attention is paid to the agreements on migration between Italy and Libya, mainly between the late 1990s and 2009, and I examine how the putative process of externalisation of migration policies from Italy to Libya impacts upon their negotiations. I argue that this case of externalisation does not merely consist of a univocal delegation of sovereignty. Therefore I conclude that the theoretical debate is still open, both with regard to the applicability of the externalisation concept to this particular case, and to its broader representativeness.