Cross-border police co-operation has increased significantly in recent decades. Law enforcement co-operation is now a global enterprise, no longer limited to neighbouring states or members of the same federal or regional political alliance. Considering that policing and criminal justice are matters located at the heart of national sovereignty, this evolution is striking. Closer examination of modes of co-operation focused on local rather than global networks of exchange, reveals a complex picture of legal, organisational and communication challenges. This article therefore explores practices of police co-operation not in the global, but within the Australian context, highlighting in particular the interaction of formal and informal co-operation mechanisms. A particular focus lies on assessing the impact of formal legal frameworks regulating police co-operation in the European Union in contrast with the informal mechanisms that have predominately characterised cross-border police co-operation in Australia.