The hypothesis of this article is that collective identity is primarily reflexive. In other words, it is given only with this process as a virtual anchor point, which can never be systematically articulated in properties but which nevertheless is analysable in terms of permanent redefinition of the parameters of involvement, i.e. of inclusion and exclusion of "the alien". The validity of this hypothesis is philosophically assessed taking into account Paul Ricoeur’s analysis of identity in terms of idem and ipse. In addition, it is legally assessed against the background of EU immigration Law and of the recently signed Constitution for Europe. The complementary dialectics of the substantive and the reflexive ideas of identity are shown within the context of relations between the management of EU external borders and the process of enlargement.