When Compromise Becomes Standoff: Joint Implementation and the Case of the European Public Prosecutor's Office

ABSTRACT This article explores endogenous problems of joint implementation in multi‐level systems. Focusing on the European Public Prosecutor's Office (EPPO), we theorize a causal mechanism of conflict deferral, whereby contentious negotiations are resolved through deliberately ambiguous legislation that postpones conflict to the implementation stage. Under conditions of joint implementation, where multiple authorities exercise interdependent enforcement powers, such ambiguity produces standoffs: situations of overlapping and incompatible jurisdictional claims over the same implementing action. Empirically, we apply theory‐testing process tracing to two conflicts involving the EPPO: vertical conflicts over competence between EU and national authorities, and horizontal conflicts in cross‐border investigations. Drawing on official documents, case law, and interviews, we show how legislative compromises locked in unresolved conflicts that systematically resurfaced during implementation. The article advances research on joint implementation by specifying the micro‐mechanisms linking legislative conflict to implementation dysfunctions and by conceptualizing standoff as a distinct implementation outcome in multi‐level governance.