Borders play a critical role in shaping our understanding of refugees. Under the modern refugee regime, people must move across international borders to obtain asylum. Borders are increasingly identified as sites of contestation; this article explores how refugees are fundamentally constitutive of modern borders regimes as states react to the movement of people with a variety of exclusionary mechanisms that, in turn, affect how those in motion are perceived. The evolving politics surrounding territorial borders between Hong Kong and the People’s Republic of China (PRC) from 1949 to 1967 illustrate how closing borders in the face of migrant mobility affected contemporary conceptions of refugees and the related possibility of obtaining refugee status. These critical years, spanning the victory of the Chinese Communist Party and the spread of the Cultural Revolution to Hong Kong, saw major shifts in the government of Hong Kong’s approach to its borders with the PRC. As a result of controls introduced by British colonial authorities, Hong Kong’s border zones changed from historically open spaces of free movement to highly restrictive and militarized barriers. At the same time, the possibility of refugeehood for migrants from the PRC vanished almost entirely. The impact of border controls imposed by colonial authorities in Hong Kong was so great that the fluid nature of migration into the colony was lost in discussions of sovereignty and illegality that sought to categorize migrants into distinct streams for the purpose of inhibiting entry.