All books in this flagship series contain carefully selected substantial extracts from key cases, legislation, and academic debate, providing able students with a stand-alone resource. The Area of Freedom, Security, and Justice (AFSJ) is now found in Title V of Part Three of the Treaty on the Functioning of the European Union. The subject matter dealt with by these provisions is important and politically sensitive, as it includes police and judicial cooperation in criminal matters, visas, asylum, immigration, and judicial cooperation in civil matters. This chapter is organized as follows. Section 2 considers the development of the three-pillar structure introduced by the Maastricht Treaty. Section 3 focuses on the rationale for the inclusion of the subject matter that comprises the AFSJ. Section 4 considers the general principles in the Lisbon Treaty that apply to all areas which comprise the AFSJ, including: Treaty objectives, competence, role of the principal EU institutions, judicial role, and an outline of the opt-outs that apply to the UK. The remainder of the chapter looks in more detail at criminal law and procedure.