This paper explores the contemporary relationship between international student migration and diaspora formation. It argues that international students have been largely absent from recent discussions of 'knowledge diasporas', where migrants' 'home' states attempt to harness and co-opt the skills and knowledge of their émigrés. This is surprising, given students' evident role in knowledge circulation and exchange. In this paper, we foreground the significance of international students but also explore their relationship to diaspora formation from a different angle. We argue that some states are increasingly engaging in (sometimes seemingly contradictory) policies designed to "obstruct" overseas diaspora formation, and these policies centre on their international student populations. Through a number of case studies and drawing on the secondary literature, we demonstrate the ways in which states are strategising to repatriate international students following their studies overseas. More broadly, we argue, this represents an alternative to popular notions of brain circulation and knowledge diasporas, chiming with a far more long-standing concern with 'brain drain'.