The Three-Pillars System of the European Union was intended to give flexibility to, and ultimately to extend, the area over which the EU could exert its influence. The Second and Third Pillars reflect a different level of integration and centralization, with the result that the Union can have input into the more politically sensitive and legally complex areas. The most well-documented pillar is the European Communities Pillar, where Community legislation takes place, and Community methods, rather than intergovernmental methods, prevail. However, it is argued that the two intergovernmental pillars - the common Foreign and Security Policy, and Cooperation in Justice and Home Affairs - make an important contribution to the increasing legal sophistication of the Unions constitution. The former has enabled the European Union to assert its own identity without compromising the sovereignty of the Member States, whilst the latter can be seen as a half-way house for subjects too sensitive for immediate integration into the Community Legal Order. This analytical examination of the combination of public international law methods and Community methods at work in Europe is essential reading for all those with an interest in the future development of the European Union.