Linked to global processes and the reconfigurations of ‘outer’ and ‘inner’ European Union (EU) borders are attempts at harmonizing migration policies across EU member-states as well as introducing an additional layer of EU citizenship to that of the state. At the same time, discourses on citizenship in many EU member-states continue to be informed by the ideal of nation-state congruence and the dogma of social and linguistic homogeneism. Combining research on regimes of language and acts of citizenship, this paper provides an analysis of discourses on language, integration and citizenship in Luxembourg. The analysis shows how disputes concerning the introduction of the formalized testing of Luxembourgish as part of the 2008 law on la nationalité luxembourgeoise ‘Luxembourgish nationality’ are intertwined with contestations over transformations of long-standing language regimes and with the issue of whether the authority of Luxembourgish is bound up with notions of anonymity or authenticity.