The establishment of the European Public Prosecutor’s Office – ‘integration with limited supranationalisation’ as a way out of the sovereignty trilemma

In 2017, twenty member states of the European Union (EU) established the European Public Prosecutor’s Office (EPPO), an EU body investigating and prosecuting offences against the EU budget. States consider criminal justice – including criminal investigations and prosecutions – as part of national sovereignty because it is linked to their monopoly on the legitimate use of force. Integration scholars contend that states only reluctantly transfer sovereign powers to supranational institutions (Moravcsik 1998). So, why did member states, by establishing the EPPO, delegate sovereign powers to a European body anyway? I argue that member states were caught between three norms: (1) to effectively manage interdependencies between states (Moravcsik 1993), like the protection of the EU budget; (2) to preserve national discretion over policies, according to ‘national sovereignism’ opposing the further transfer of powers to supranational institutions (Basile and Mazzoleni 2020; Baldini et al. 2020); and (3) to commit to the ‘European idea’. By establishing de novo bodies (Bickerton et al. 2015) like the EPPO, states realise ‘integration with limited supranationalisation’ and thereby respond to all three norms of this trilemma (H1). How the involved actors have problematised the EPPO and its modalities matters greatly in explaining why member states joined the body. A discourse analysis of original document and interview data shows how the European Commission promoted a narrative on the need for the EPPO, according to a supranational conception of the body, also shared by certain states in the Council of the EU. A second group of states was more reluctant to the transfer of powers to a European body. They reframed the EPPO’s modalities according to their ‘national’ conception to make its establishment acceptable to them. The ‘supranationalist’ camp had more interest in achieving agreement because establishing the EPPO was the most ‘European’ solution conceivable. The ‘national’ camp could therefore credibly threaten with non-agreement to shape the outcome according to their preferences: they agreed to delegate sovereign powers only under the condition of a more ‘sovereignty-friendly’ architecture of the body (Met-Domestici 2017) (H2). Since the outcome must accommodate partly contradictory interests, the described trilemma translated into ambiguity and complexity of the EPPO’s structure (H3) and a ‘dilution of sovereignty’ between the European and national level. This paper provides a political scientist account of an EU body that has so far almost exclusively been studied by legal scholars. By relying on lessons from EU integration literature, we gain insights on a particularly interesting case of delegation of powers in one of the most ‘sovereignty-sensitive’ fields of the EU, that is, EU criminal justice. The case study shows how sovereignist frames used by national executives conflict with the wish to find effective solutions to interdependency problems and to show commitment to the ‘European idea’. The need to accommodate these conflicting norms explains the complex outcome of negotiations. However, the particularly strong sovereignist claims of some EU member states also explain their non-participation in the project – which was ultimately realised through enhanced cooperation among only twenty-two out of twenty-seven member states.