This volume examines the underlying foundations on which the European Union's counter-terrorism and police co-operation policies have been built since the inception of the Treaty on European Union, questioning both the effectiveness and legitimacy of the EU's efforts in these two critically important security areas. Given the importance of such developments to the wider credibility of the EU as a security actor, this volume adopts a more structured analysis of key stages of the implementation process. These include the establishment of objectives, both at the wider level of internal security co-operation and in terms of both counter-terrorism and policing, particularly in relation to the European Police Office, the nature of information exchange and the 'value added' by legislative and operational developments at the European level. It also offers a more accurate appraisal of the official characterisation of the terrorist threat within the EU as a 'matter of common concern'. In doing so, not only does it raise important questions about the utility of the European level for organising internal security co-operation, but it also provides a more comprehensive assessment of the EU's activities throughout the lifetime of the Third Pillar, placing in a wider and more realistic context the EU's reaction to the events of 11 September 2001 and the greater prominence of Islamist terrorism.