In this article Peter Joyce, author of The Policing of Protest, Disorder and International Terrorism in the UK since 1945, reviews the potential difficulties facing the UK’s security during the Brexit process.

Events that occurred at Westminster on 22 March 2017 graphically illustrated the death and destruction associated with contemporary terrorism. This is frequently conducted on an international stage – attacks are planned in one country, executed in another and owe their inspiration to views and ideas disseminated on global forms of communication such as the internet.

However, tackling international terrorism effectively requires cooperation across national borders in areas that include intelligence / information-sharing and law enforcement. Although the European Union is not the only forum through which international responses to terrorism can be fashioned or coordinated, it is an important forum for the UK because of the proximity of areas such as Molenbeek in Brussels, which in recent years has been an area of significant importance focused around jihadist terrorism, including activities related to the Paris 'rolling attacks' in November 2015.

This situation begs the question as to whether this is a good moment for the UK to put itself in a position that may potentially exclude it from EU mechanisms which seek, through the joint action of member states, to counter international terrorism.

The EU has played an important role in combating terrorism and related forms of criminal activity such as money laundering. This has taken the form of putting forward a range of proposals for the adoption of member states in order to secure a common approach to counter terrorism. These have included the 2001 EU Action Plan to Combat Terrorism, the 2004 EU Plan of Action on Combating Terrorism and the 2005 EU Counter Terrorism Strategy.

A number of mechanisms have also been developed under the auspices of the EU to facilitate joint action by members states. These include Europol (whose work in connection with terrorism is discharged by bodies that include the European Counter-Terrorism Centre), the European Judicial Network in Criminal Matters and the European Arrest Warrant (EAW). Additionally, the UK – although outside of the borders aspect of Schengen Agreement and Convention – has participated since 2015 in the Second Generation Schengen Information System (SIS). All of these initiatives are of integral relevance to the EU-wide response to international terrorism.

The referendum campaign in June 2016 was dominated by negativity, in particular concerning immigration. It gave no prominence to the ways through which membership of the EU had provided for the safety and security of UK citizens.

It is perfectly feasible that the UK could negotiate bespoke arrangements to retain membership or association with bodies such as Europol, the EAW and the Schengen SIS. These would be complex to construct but there are incentives to encourage the EU to facilitate these arrangements.

The UK plays an important role in international affairs through its membership of the UN Security Council (which also performs an important role in coordinating global responses to terrorism) and through other arrangements that include the 'five eyes' alliance of the UK, USA, Canada, Australia and New Zealand (which secures joint cooperation in relation to signals intelligence). The UK has also been an active participant to joint EU endeavours such as the EAW. There are thus strong incentives for the EU to facilitate such involvement post-Brexit.

However, there are potentially counter veiling pressures that might make it difficult for continued UK involvement in EU security measures following its departure from the EU.

Brexit negotiations are currently dominated by the theme of negotiating a trade deal between the UK and the EU and concerns have been expressed that the government's continued willingness to be involved in existing EU initiatives to combat international crime and terrorism may be used as a bargaining chip in discussions relating to securing a favourable trade deal with the EU. If the latter is not secured, the former may be abandoned.

These negotiations became clouded in early April by the inclusion of Gibraltar in the Brexit guidelines announced by the President of the EU Council, Donald Tusk. These indicated that when the UK had left the EU, no trade agreement between the EU and the UK would apply to Gibraltar without the agreement of the governments of Spain and the UK. Theoretically, this could place Gibraltar outside of any trading arrangements that are eventually constructed with the intention of coercing Gibraltar into union with Spain in order to safeguard the economic future of its citizens. The raising of this issue may serve to stiffen the resolve of those who favour  a 'hard Brexit'.

This would entail the UK walking away from the EU without any deal on access to the single market and (probably) to the EU customs unions. Such a situation would make it very difficult for provide for the UK's future involvement in bodies such as Schengen's SIS and Europol that play an important role in helping to protect the UK against contemporary forms of international terrorism.

Peter Joyce is a Principal Lecturer in Criminology at Manchester Metropolitan University, UK. He has published widely in the areas of politics and he is also a regular contributor the journal of the Association of Chief Police Officers, Policing Today.