As the threat of a no-deal Brexit looms closer, it is becoming increasingly clear that such a scenario would significantly hamper counterterrorism efforts in both the United Kingdom and Europe.
As an EU member, the UK is party to European institutions such as the European Arrest Warrant, a system of warrants valid throughout the European Union, and Europol, the EU-wide law-enforcement body that combats terror and organized crime. The UK also receives additional European data including fingerprints, DNA, and passenger flight information. Should it leave the EU without a deal establishing a continued partnership on such initiatives, it will lose access to European intelligence and risk becoming unaware of potential terrorist threats within their own borders.
This will adversely impact Europe as well. For every suspect arrested on a European Arrest Warrant, British authorities arrest eight EAW suspects from other states, so the benefit to European countries from British forces is huge. Given the extensive travel between Europe and the UK, it is critical that the two cooperate on intelligence so that no criminal may slip through borders unnoticed. Should this cooperation end, it is likely dangerous individuals will cross between Britain and Europe without notice.
If no deal codifies the partnership between British and European law enforcement, then both the EU and the UK are in an extremely risky position. To avoid the possibility of turning the UK into a de facto safe haven for European criminals, a no-deal Brexit must be avoided, and the UK must negotiate a continued partnership with the European Union.