Abstract The pitfalls of the relationship between European and national judges constitute a well-travelled ground in literature, especially with regard to ‘sagas’ over the reconciliation of national sovereignty with EU law primacy. Hence, the contribution that this article is attempting to make is to explore the judicial understanding and potential of the concept of constitutional identity in the light of the newly-introduced Article 4(2) TEU by the Treaty of Lisbon, which makes it explicit that national identity encompasses constitutional specificity. A number of questions are raised and discussed. For instance: How has the Court of Justice of the European Union (CJEU) been adjudicating on issues pertaining to the constitutional identity of the Member States pre- and post-Lisbon? How far can Member States stretch the concept to avoid the tidal effect of EU law upon their legal systems? For the sake of clarity, two notions of constitutional identity are identified and presented in this article: One related to the CJEU’s case law, where ‘constitutional identity’ has been invoked by defending Member States as a qualified derogation from their EU law obligations (a ‘shield’) and another, inherent in the German Constitutional Court’s (BVerfG) use of ‘constitutional identity’ as a break to an unprecedented transfer of competences to the EU and a tool of judicial review of national implementation measures of secondary legislation (a sword). The arguments advanced hereafter suggest that the implications of identity retention as a ‘shield’ may not be far-reaching since the CJEU has, through a pragmatic use of the loyalty and proportionality principles, succeeded in reducing its effect to the bare minimum. On the other hand, as a judicial review mechanism, the German paradigm demonstrates that, as a ‘sword’, constitutional identity retention comprises, largely, a theoretical possibility. These assumptions aside, it is concluded that constitutional identity retention may provide both national judiciaries and legislatures with new opportunities to participate in trans-national constitutional development through monitoring and assessing the compatibility of the exercise of EU competence with the requirements of national constitutions.