This chapter examines reactions – and resistances – within national executives to the EPPO, an endeavour with sensitive implications for national sovereignty. It interprets the gradual emergence of national support with reference to domestic institutional contexts, but also key ideational processes linked to the articulation between state identity and European integration, different understandings of sovereignty, and the construction of a national interest in the fight against transnational crime and the protection of the EU budget. It shows that, as a result of those ideational processes, a critical mass of member states ultimately agreed to setting up the EPPO under the condition that its structure and powers allowed for more influence and control by national actors. The chapter concludes that the final shape of the EPPO – a result of conditions prescribed by national governments – corresponds to intergovernmentalist dynamics, making the EPPO a product of both supranationalist and intergovernmentalist tendencies.