Under what conditions do authoritarian states exercise control over populations abroad? The securitisation of cross-border mobility has been a common theme in examining immigration policies in the Global North. The securitisation of emigration and diasporas in non-democratic contexts remains neglected; this is particularly true with regard to Arab states' extraterritorial authoritarian practices. This article argues that authoritarian states develop a range of migration policies that are driven by the contradictory pressures of economic and political imperatives or, put differently, an illiberal paradox: if a state does not expect economic gains from cross-border mobility, it is more likely to securitise its emigration policy; otherwise, it is more likely to securitise its diaspora policy. The article illustrates this trade-off via a most-similar comparison of Algeria, Libya, Tunisia, and Morocco. Drawing on Arabic and non-Arabic primary and secondary sources, it sketches a novel area of research on migration and security.