The European Union (EU), as unprecedented institutional and polity project, is responsible for the fulfilment of a set of policy goals that go beyond the mere sum of the interests of its Member States. The establishment of an ‘area of freedom, security and justice without internal frontiers, in which the free movement of persons is ensured in conjunction with appropriate measures with respect to . . . the prevention and combating of crime’ is probably one of the most demanding goals of the integration process, whose fulfilment requires commitment to coherent action on several levels: vertically, between the EU and the Member States, through incorporating the implementation of the Treaty objectives in the development of their respective criminal policies, and horizontally, between the Member States themselves, by developing mutual trust.