A Common Security and Defence Policy: Limits to Differentiated Integration in PESCO?

The use of Permanent Structured Cooperation (PESCO) by the European Union to manage defence cooperation between its Member States is the most recent example of Differentiated Integration (DI) in the EU. Yet differentiation may come at a price. The main aim of the present Article is to assess to what extent defence cooperation under the umbrella of PESCO can be cut up in pieces and yet still be considered a common defence adhering to the EU’s general principles of consistency and sincere cooperation. The question, therefore, is whether DI in PESCO is limited by these principles, and consequently, whether the CSDP, despite the differentiation, still contributes to a common policy. In short, the question is whether there is a tension between commonness and differentiation in EU security cooperation.