A Laboratory of Constitutional Development: Domestic Differentiation and the Effective Application of EU Law in the Area of Freedom, Security and Justice

Balancing differentiation and effectiveness is an inherent part of European integration, taking into account national specificities and allowing them to be accommodated within an enlarged and constitutionally advanced Union of states and people. The AFSJ provides an excellent case study of the extent to which EU law allows for differentiation. Since the AFSJ deals with areas intimate to national sovereignty (such as asylum and criminal law), striking a balance between integration and differentiation can be challenging, to say the least. However, at the same time, the acceptance of differentiation has allowed EU law in AFSJ to grow organically and to develop into areas that the original drafters of the treaty never envisaged would be possible. This chapter serves to illustrate the opportunities and challenges presented by differentiation in the context of the AFSJ, arguing that it is a core element equally of EU legislation and adjudication by the ECJ. It argues that while the EU has accepted and adopted differentiation as an expression of subsidiarity, conferral, and constitutional identity affording a wide margin of appreciation, it has let it grow within the confines of a sophisticated set of EU law principles, concepts and ideals, such as mutual recognition or solidarity, making differentiation a component of a greater effectiveness of EU law. It is therefore the product of a balancing exercise in EU law that weighs national and EU constitutional specificities, opting for a measured and integration-friendly differentiation.