Identity is a key, but vague, ambiguous and polysemic concept of public law. In EU law, the concept underwent a process of legalization: it emerged as a political clause in the Treaty of Maastricht and gained constitutional meaning after the Treaty of Lisbon. The article traces this process of legalization, arguing that even though the constitutionalization of the identity clause in EU law was primarily addressed to the Court of Justice of the EU, a major role in this process has been played by national courts. The article, however, claims that the process of transformation of the identity clause is not over, and that currently the concept is being subject to abusive and dangerous manipulations. The article supports a comprehensive reading of the identity clause in EU law within the broader context of EU fundamental principles. In particular, the article claims that a tight connection of the identity clause should be kept with the democratic mandate of the EU. This connection emerged very clearly in the Maastricht formulation of the Treaty on the European Union but is still now a viable remedy to reject Member States’ appeals to protect unconstitutional constitutional identities.