The Maastricht treaty on the European Union (EU) erected a three-pillar edifice of European integration whose third pillar comprised various forms of cooperation in justice and home affairs. Many practices had existed much before 1992 and their inclusion into the new organization was a kind of cosmetic surgery. That face-lifting of cooperation in justice and home affairs had obvious consequences for the nature of the third pillar and the overall balance of EU policies. The third pillar was a strictly intergovernmental area where the EU members kept their sovereign right to decide upon their home affairs and judicial cooperation, as well as regulate migration flows and safeguard their national borders.

EC institutions did not have much say on those matters, and any progress of cooperation depended on consensus between the members. The Maastricht treaty established legal/formal and institutional grounds for EU cooperation in managing internal security through intergovernmental consultations regarding the movement of persons in the EU, and concomitant flanking measures in the fields of police and judicial cooperation. EU politics of internal security was formally strengthened in the Amsterdam Treaty, and practically through incorporation of acquis Schengen into the legal framework of the Union. The gradual widening of the Schengen area, the abolition of controls at internal borders and the reinforcement of flanking measures, especially at external borders, allowed the EU to set up a comprehensive and relatively efficient system of internal security.

Although the Amsterdam treaty, reforming the EU, intended to improve the fluctuation of numerous policy fields, its provisions concerning justice and home affairs were controversial. Firstly, a relatively simple and transparent structure of third-pillar cooperation was replaced by a multilevel asymmetrical and entangled cross-pillar construction in an "area of freedom, security and justice." Provisions relating to immigration, visas, asylum and other policies related to free movement of persons were transferred to the Community pillar. The third pillar was reduced to police and criminal justice cooperation. The Schengen acquis was inserted into the framework of the EU although its provisions were granted a special autonomy.

Discussions about the reform of the EU have dominated a general political and theoretical discourse on European integration at the threshold of the 21st century. A host of supranational institutions and intergovernmental bodies along with politicians and government officials from the EU members have perseveringly deliberated upon the most suitable and desirable shape of a future EU. The 2007 Lisbon treaty ended the long and tortuous trip to a new arrangement for European integration although its fate is still undecided. Moreover, the formal abolition of the pillar structure was partially undermined by special provisions concerning, first of all, internal security matters, especially police cooperation and criminal justice.

The process of constitutionalisation of the EU came amidst a great global security debate. The symbolic and political impact of the 9/11 terrorist attacks on the US, when Western civilization lost the feeling of stability and entered a new stage: a ‘war on terror,' brought about new challenges for the EU in the area of security. Transnational processes, in which the EU and its Communities have, for decades, assumed a leading and creative role, changed the traditional perception and understanding of security.

One of the objectives of European integration has been to make inhabitants of the continent feel safer and more confident in the institutions of public life. The challenge of transnational threats such as terrorism, cross-border organized crime, large-scale migrations, asymmetrical conflicts or WMD proliferation had also to be met by the European states. Confronted for decades with such disquieting events and phenomena, the Europeans managed to work out, within the framework of European integration processes, certain arrangements allowing for more effective and long-term cooperation in preventing and combating the major threats to European security.