The UK works inter-governmentally with its EU partners to adopt common positions and diplomatic approaches, undertake joint actions and deploy military and civilian missions under the Common Security and Defence Policy (CSDP). The Iran nuclear deal framework agreed in 2015 is an example of an issue where coordinating negotiations and sanctions through the EU helped the UK in one of its top foreign policy priority areas. However, EU foreign policy has been less successful in responding to recent challenges such as terrorism and migration, and divergences have been noted between member states about priorities and resources for pursuing EU foreign and security policy. Non-EU member states can align themselves with EU common positions and participate in sanctions on a voluntary basis, but since they have no formal influence over the formulation of the policy, it is not clear to what extent the UK would seek to do this in the future.
The UK has participated in a number of military and civilian CSDP missions since 2003, and is currently supporting naval operations in the Mediterranean and Somalia. Sir Michael Fallon, the Secretary of State for Defence, has said that the UK’s withdrawal from the EU should not inhibit future cooperation with missions that are in the national interest, although he has not elaborated on what form such cooperation would take. Non-EU member states have contributed to almost all CSDP missions in varying formats. The UK could continue its defence cooperation with European partners through NATO, through continued participation in EU structures and operations as a third country nation, or through bilateral relations with EU partners.
The UK has opted in to a number of police and criminal justice measures which facilitate cooperation on intelligence sharing, security and counter-terrorism, such as the European Arrest Warrant, Europol and various EU-wide databases. There are precedents for arrangements which allow non-EU member states to participate in some of these measures, although not always with the same level of access or influence as member states. Commentators agree that it would be of mutual benefit for the UK and its European partners to cooperate on intelligence, security and counter-terrorism, but it has been argued that bilateral and informal cooperation play an important role in this area alongside formal EU mechanisms.
