Chapter Six: The Justice and Home Affairs (JHA) cross border measures
39. Most interests for Justice and Security fall under the EU area of JHA. The JHA area is unusual relative to other existing areas of EU activity. Since the Lisbon Treaty  , which entered into force in 2009, the UK Government chooses which JHA criminal cross border measures to take part in rather than being automatically bound – and exercises the right to "opt in" or "opt out" of individual pieces of JHA legislation. As a result, the UK does not participate in a number of measures, for example those in relation to counter terrorism. However, the UK has chosen to opt into a number of significant, important JHA cross border measures.
40. The JHA criminal cross border measures create a set of instruments for preventing, investigating and prosecuting crime. The value of the suite of JHA measures, taken together, is greater than the sum of its component parts. They work together as a package to allow rapid information sharing and effective co-operation between police and prosecutors across the EU. The loss of any one measure would affect, perhaps to an extent which cannot be fully predicted, the effectiveness of the suite of measures working as a whole. For example, the effectiveness of the European Arrest Warrant which facilitates extradition between EU Member States and the jurisdictions of the UK, has been enhanced by UK participation in the Schengen Information System ( SIS II) which enables law enforcement across Europe to establish, in real time, whether an individual is the subject of an European Arrest Warrant ( EAW). These measures work in both directions, benefiting both the UK and the other EU Member States.
41. What follows below are examples which seek to offer a sense of some of the key JHA measures that we stand to lose and the potential impact in bold of that loss on the capabilities of the Justice system.