The entry into force of the Treaty establishing a Constitution for Europe will bring significative changes into EU criminal policy. Competence in the area of freedom, security and justice is a shared one (I-13, I-14) and therefore submitted to the principles of coferral, subsidiarity and proportionality, but there are other areas of exclusive competence of the EU, in which it could legislate, even in the criminal aspects, with european framework laws. This possibility, together with establishing the minimun rules concerning the definition of criminal offences and sanctions in the areas of particularly serious crimes with a cross-border dimension (III-271), comes to join the traditional fields of police and judicial cooperation (Europol-Eurojust) in criminal matters, now intensified with the creation of a European Public Prosecutor's Office, with important powers that could be extended (III-274). All this leads to think that the way to an authentical european criminal policy that overcomes the traditional consideration of criminal law as an exclusive competence of each Member State is open.