The relationship between marriage and citizenship was implicit in the practices of most democratic states during the nineteenth and early twentieth centuries. The policy of depriving women who married foreigners of their citizenship was legally codified only with the process of ‘nationalisation’. In the particular case of Switzerland, the practice was not codified until 1941, at the height of the movement of peoples unleashed by the Second World War, and it was only fully dismantled in the 1990s. This article analyses the discursive webs linking gender construction, nation state and legal system during the controversies surrounding the marriage rule in Switzerland between 1917 and 1952. It explores the formative role of gender in the process of delineating the practices of inclusion and exclusion and in shaping the internal boundaries within the nation between foreigners and those who belonged: citizens.