Since the beginning of the 21st century, a variety of legal statutes have been developed for legal residents in Europe, which undermine the principle of equal treatment and non-discrimination under certain directives. The discretion that such directives grant to EU Member States is producing such a level of social injustice and human segmentation that European security and justice is put at risk. For this reason, we consider that an immigration code is essential for generating a common legal basis that prevents states from adopting unreasonably favourable treatment of certain types of highly skilled workers, while placing others at a clear disadvantage. In this paper, we will analyse the Constitutive Treaties and the legal instruments drafted by the European institutions, in order to find a firm basis of legal legitimacy from which to encourage a European Code of Immigration.