This papers aims to open a theoretical space to analyse the ‘acts’ of citizenship through which the third-country nationals become claimants of rights and implicitly or explicitly question the boundaries of the political and the nature of existing divisions upon which EU citizenship is grounded. After providing a critical overview of the social citizenship studies through the particular lens of migration scholarship, it concentrates on the mutual constitution of EU citizenship and third-country nationals (i.e. the citizens of non member states of EU) as the ‘outside’ of EU citizenship. The nature of the ruptures EU citizenship introduces to the fellow residents of EU are investigated through the application of International Private Law in Germany from the perspective of the subject positions it instantiates and the sites of contention it creates. In order to highlight the importance of temporal and spatial grounding of acts of citizenship, the following section approaches to such acts as contentious performances. The last section argues for the necessity to go beyond methodological nationalism and ethnic lens in migration scholarship in studying citizenship and the need for selection of sites and objects of research accordingly.