145 The development of EU citizenship has been regularly, albeit not too intensively, discussed in recent decades (see, e.g., Closa 1995; Kostakopoulou 2007; Besson and Utzinger 2008; Baubock 2007; Bellamy 2008; Wollenschläger 2011; Wiener 1998), but it has rarely been analysed as a contested concept (for one exception, see Mäkinen 2015). In this context, this chapter will help to fll a gap in research. Its aim is to analyse in detail how, and by whom, EU citizenship has been con- ceptualised and shaped in order to discuss and answer three crucial ques- tions (for earlier versions of parts of the following, see Wiesner 2018; Wiesner et al. 2017, 184–99): How can a conceptual innovation, such as Union citizenship, be flled with meaning and also with a new institu- tional practice? Which conficts, actors and strategies are decisive in these processes? And what particular shape does the concept of citizenship take on in the EU, and which new questions does this new shape give rise to? IMPLEMENTING CONCEPTUAL INNOVATIONS: THE CASE OF THE DEVELOPMENT OF EU CITIZENSHIP The development of EU citizenship has been decisively shaped by a typical interrelation between conceptual innovations, law-making and their being put into institutional practice. More exactly, it is a common Inventing and Shaping EU Citizens © The Author(s) 2019 C. Wiesner, Inventing the EU as a Democratic Polity, Palgrave Studies in European Political Sociology, https://doi.org/10.1007/978-3-319-94415-9_10