Over the past 15 years, Luxembourg nationality legislation has undergone a paradigmatic shift from being an “insular regime” that restricted access to citizenship for both immigrants and emigrants, as well as their descendants, to an “expansive regime” that is inclusive towards these groups. This paper addresses this “Copernican revolution”, outlining the comprehensive legal changes, assessing the impact of citizenship acquisition, and analysing the factors that explain the paradigm shift in Luxembourg nationality law in the new century. The paper focuses on two elements of this shift: the sizeable impact of new option procedures for immigrants and their descendants, and the unintended creation of a second strategic citizenship for contemporary descendants of Luxembourg emigrants from the 19th century. The paper concludes that the changes in Luxembourgish nationality law reflect simultaneous political pressures for de- -ethnicisation and re-ethnicisation in response to globalization and international migration.