Attention is given to the so-called three pillars of the Maastricht, Amsterdam, and Nice treaties: Pillar I (on supranational matters subject to binding legislation passed by supranational institutions); Pillar II on external security; and Pillar III on justice and home affairs (the intergovernmental pillar now dedicated to the realization of an European Union of "freedom, security, and justice"). The implementation of Pillar III under the enlargement of the European Union to central and eastern European countries is the focus of the second part of this chapter. The chapter alludes to some of the particular difficulties and challenges posed by Pillar III of the Maastricht Treaty and its revised versions in the Amsterdam Treaty and Nice Treaty for the process of European Union enlargement. The chapter argues that unless steps are taken to focus on and protect the "internal security acquis" of the European Union, then enlargement might become an excuse to postpone the attainment of freedom, security, and justice in the expanded European Union and vice versa. The key goal of Pillar III is to "maintain and develop the Union as an area of freedom, security, and justice, in which the free movement of persons is assured in conjunction with the appropriate measures with respect to external border controls, immigration, asylum, and the prevention and combating of crime" (preamble to the Amsterdam Treaty). Member states remain responsible for preserving law and order within their boundaries. The chapter discusses uniformity versus diversity in an enlarging European Union, the compatibility of transitional measures with "freedom, security, and justice," and the importance of developing a multi-pronged strategy to acclimate the applicant states to the norms and expectations of democratic practice and culture. 9 notes and 15 references