Citizenship has emerged as an important topic of research on migration and migrant integration since the 1980s. Before this there was little connection between migration research and the legal literature on nationality law or political theories and sociological analyses of citizenship in a broader sense. This mutual disinterest is not difficult to understand. On the one hand, in traditional overseas countries of immigration, immigrants’ access to citizenship and eventual naturalisation was taken for granted as a step in a broader process of assimilation. On the other hand, in Europe the largest immigration contingents had emerged from the recruitment of guestworkers who had been invited to stay only temporarily and were never perceived as future citizens.

Both perceptions were eventually undermined when the dynamics of the migration process interacted with political developments towards a more inclusive conception of citizenship. Family reunification turned guestworkers into settled immigrants. Many among these maintained, however, strong ties to their countries of origin. For these migrants, retaining the nationality of origin was a natural choice both for its instrumental value as a bundle of rights and because of its symbolic value as a marker of ethno-national identity. At the same time, the rights of permanent residents in major democratic receiving states were upgraded in many areas or equalised with those of citizens. Finally, more and more countries of immigration abandoned the existing consensus in international law that those who naturalise have to renounce their previous nationality and a growing number of sending countries also accepted multiple nationality among their expatriates. All these developments have blurred the previously clear line separating aliens from citizens. This could not remain without consequences. While some observers welcomed these trends as heralding a new cosmopolitan era in which state-bound citizenship would eventually be overcome, others were concerned about migrants’ multiple loyalties, their apparent freeriding on citizenship rights without duties and their political mobilisation according to ethnic or religious identities.

In this report we trace the main steps in these developments, summarise the state of research and emphasise controversies between competing interpretations. The report does not, however, aim at a comprehensive and high level overview. It reflects approaches that have guided past research carried out by members of the IMISCOE cluster on citizenship, legal status and political participation and it points towards a future research agenda to which the cluster hopes to contribute.