Judicial cooperation in criminal matters is based on the principle of mutual recognition of judgments and judicial decisions, and includes measures to approximate the laws of the Member States in several areas. The progressive elimination of border controls within the EU has facilitated considerably the free movement of European citizens, but has also made it easier for criminals to operate transnationally. In order to tackle the challenge of cross-border crime, it is necessary to have measures to promote judicial cooperation among the Member States in criminal matters. The starting point is the principle of mutual recognition. Specific measures have been adopted to fight transnational crime at EU level.