Cross-border police cooperation is a very sensitive issue because it touches upon state souvereignity and in particular upon the state’s monopoly on the use of force. This explains on the hand why international police cooperation in the past always has been a very secretive component of foreign policy and on the other hand why it blossomed up in that many ways, in that many fields and at that different levels in the framework of the European Union. The incentives for this important development came from the TREVI initiative and the Schengen Agreement but the Treaty of Maastricht has been in the end the main source of this hugely important development. Nevertheless the reform of the Maastricht Treaty by the Treaty of Amsterdam was needed to bring about a breakthrough that via the Tampere Program and the Hague Program has not only reinforced the institutionalization of police cooperation (apart from Europol also CEPOL, Frontex, Police Chief’s Task Force) but also its ‘operationalization’ in the form of a.o. the Convention on Mutual Assistance in Criminal Matters, the Prum Treaty and the Swedish Framework Decision. In contrast to the enormous potential of the Lisbon Treaty with regard to police cooperation the Stockholm Program contains however quite limited ambitions and proposals in this field. It is as if the European Council – knowing how sensitive the issue is – did not dare to exploit the new possibilities.