270 K. Henrard citizenship, the manifold conceptions of citizenship that have developed over time (including supra-national, sub-national and transnational citizenship) and its relevance for a good understanding of nationality.1 Secondly, this contribution provides the overarching framework for the special issue while identifying the salient discussion points regarding nationality and international law that will be teased out in the articles of the special issue. A recurring theme throughout this article is the extent to which questions about the core notion of nationality, and the special bond that is supposed to represent between a natural person and a state, can be seen to inform choices about modes of acquisition and legitimate instances of deprivation, as well as rights and duties ‘reserved’ for nationals.2 Indeed, the type of criteria set for acquisition of nationality arguably allows one to reflect on the bond nationality is supposed to represent, while the protections reserved for nationals similarly offer some indication of the nature of that bond.3 The importance of these rights and additional protection layers contingent on nationality furthermore signal the importance of having a nationality. However, when (human) rights are increasingly detached from nationality, what explains the sustained vigor of the fight against statelessness, the increasing recognition of a human right to a nationality and the limited possibilities for deprivations of nationality (also when fighting terrorism)? All of the above themes tie in with controversies and challenges regarding dual or even multiple nationalities, both from the perspective of public and private international law. Another central theme, not only for this article but also for the special issue as a whole, concerns the implications of the changed circumstances of the current mobile world with its multiple migration streams, as compared to the times when nationality as a legal category was conceived, and most people lived and died in the area where they were born. To what extent and in what way do these changed circumstances affect the way we understand nationality, the special bond it is supposed to reflect (including the degree to which it can be commodified), and its ongoing relevance as connecting factor for rights in international law. The article is structured in five parts. The first part (Sect. 2) provides a historical conceptual account of the development of the multi-dimensional notion of citizenship and its shifting spatialities, until the era in which the nation-state became the central point of reference, and nationality as legal concept emerged. The state may still be the central point of reference, the reality of multiple levels of governance 1 Liebich (2010) highlights in this respect that nationality laws and changes in this respect are inspired by (changing) conceptions of citizenship. Note that in the literature at times the distinction is made within the legal field between citizenship and nationality with the former referring to the status and rights in terms of national law (within a particular state), whereas the latter would concern the status and rights in terms of international law, see, inter alia, Rubenstein (2004), p. 3. 2 This close interrelation is nicely captured by Crawford (2012) who argues that: ‘nationality is a legal bond having as its basis a social fact of attachment, a genuine connection of existence, interests and sentiments, together with the existence of reciprocal rights and duties’, p. 513. 3 The institute of diplomatic protection may not translate in an actual right of nationals, it does constitute an additional layer of protection for nationals, and is thus similarly relevant for the study of nationality in international law. 123