In this chapter I examine female marriage migration to South Korea from Vietnam as a transnational case study, to explain the discriminatory consequences of South Korea’s laws and policies on nationality which frame such migration as ‘a critical project for the nation-state’ (Toyota M. Citizensh Stud 12(1):1, 2008, p. 3). Through a socio-legal study, I demonstrate how notions of gender, race, culture and identity shape the internal border for marriage migrants from Vietnam, through laws and policies in South Korea. I argue that responses to female marriage migration from Vietnam has created vulnerabilities, through nationality laws, which are reinforced through instrumental policies on labour migration and commercial regulation of marriage. These laws and policies entrench the unequal position of Vietnamese marriage migrants in the transnational marriage migration ‘market’ to create ‘structural vulnerability’ through the power and structures of the state.