This book provides new insights into police cooperation from a comparative socio-legal perspective. It presents a broad analysis of comparable police cooperation strategies in two systems: the EU and Australia. The evolution of regulatory trends and cooperation models is analysed for both systems and possible transferable strategies identified. Drawing on interviews with practitioners in the EU and Australia this book highlights a number of areas where the EU can be compared to a federal system and addresses the advantages and disadvantages of being a Union or a federation of states with a view to police cooperation practice. Particular topics addressed are the evolution of legal frameworks regulating police cooperation, informal cooperation strategies, Joint Investigation Teams, Europol and regional cooperation. These instruments foster police cooperation, but could be improved with a view to cooperation practice by learning from regulatory techniques and practitioner experiences of the respective other system.