The external relations of the EU, in terms of counter-terrorism measures in particular and cross-border law enforcement in general, is perhaps the most complex issue to be addressed in this book. The most developed external relationship of the EU in this context is with the US. EU relations with the US, with the exception of international trade, both bi-laterally, and via the World Trade Organization (WTO), are seen as being ‘first and foremost policy and security oriented’. 1 However, this is not the only such relationship. The focus of the Stockholm Programme, signed off in December 2009, has a heavy emphasis on the development of other relationships, and not necessarily with traditional strategic partners which would have had a shared legal framework, a shared approach to policing and other law enforcement histories. The focus of this chapter is therefore to introduce the area of the external law enforcement relations of the EU, and to develop the analysis to deal with the highly developed legal relations with the US. A selection of the balance of the external relations of the EU in this area is dealt with in Chapter 8 of this book.