This contribution aims to explain how European Criminal Law can be understood as constitutive of European identity. Instead of starting from European identity as a given, it provides a philosophical analysis of the construction of self-identity in relation to criminal law and legal tradition. The argument will be that the self-identity of those that share jurisdiction depends on and nourishes the legal tradition they adhere to and develop, while criminal jurisdiction is of crucial importance in this process of mutual constitution. This analysis will be complemented with a discussion of the integration of the first and the third pillar as aimed for by the Constitutional Treaty (TE), which would bring criminal law under majority rule and European democratic control. Attention will be paid to two ground breaking judgements of the European Court of Justice (ECJ) that seem to boil down to the fact that the Court actually manages to achieve some of the objectives of the CT even if this is not in force. This gives rise to a discussion of how the CT (and related judgements of the ECJ) may transform European criminal law in the Union to EU criminal law of the Union, thus producing an identity of the Union next to the identities prevalent in the Union. The contribution concludes with some normative questions about the kind of European identity we should aim to establish, given the fact that such identity will arise with further integration of criminal law into the first pillar.