Was first introduced at the supra-national level under the Treaty of Amsterdam and is now an area in which qualified majority voting is widely used, in accordance with the provisions of that Treaty.
Is part of the Area of Freedom, Security and Justice , together with the community provisions on asylum.
The future
The EU Constitution proposes that the Area of Freedom, Security and Justice becomes a shared competence - EU law would therefore suppress member states' existing legislation and right to legislate in this area.
Links
http://www.europa.eu.int/comm/......police/doc_police_intro_en.htm