From Europol to isolation: how Brexit weakened criminal justice

As any detective would tell you, conducting criminal enquiries or seeking to arrest a wanted criminal in the UK can be challenging, but once an international dimension is involved, that complexity is multiplied. Differences in legal systems, laws, languages, policing and judicial cultures and procedures all create significant barriers. Throughout most of the 20th century, these challenges were managed mainly through Interpol, an informal club of policing agencies set up in 1923. However, Interpol had no formal judicial role. Its function was largely limited to facilitating the exchange of police information and relaying messages between police forces of different countries.

An outdated system

When judicial assistance was required from other countries, European states relied on treaties established by the Council of Europe, notably the 1959 European Convention on Mutual Assistance in Criminal Matters and the 1957 European Convention on Extradition. These treaties required an International Letter of Request (ILoR) to be prepared by the requesting country and forwarded to the receiving country.

These documents were usually lengthy, and needed to be translated into the language of the receiving country. They had to include extensive details including a full overview of the crime, the state of the investigation, the relevant legislation, the suspects concerned or the person whose extradition was sought. It needed to set out the evidence or information sought and proof that the offence under investigation also existed under the laws of the receiving country. Typically, they spanned dozens of pages and took a considerable time to prepare and translate.

A streamlined process

Things improved when the Treaty of Maastricht, which established the European Union, was signed in 1992. It brought police and judicial cooperation into the ambit of the EU for the first time. This new policy area, referred to as the Justice and Home Affairs ‘pillar’, saw the establishment of Europol and Eurojust, which were EU judicially empowered versions of Interpol for the Union’s police and investigating judges. The UK played a leading role in developing Europol, with Sir Rob Wainwright leading the organisation for many years.

Europol and Eurojust coordinated many new and successful judicial initiatives across the EU, all of which were designed to facilitate and streamline cross-border criminal investigations. These included:

The European Arrest Warrant (EAW) which simplified extradition procedures.
Joint Investigative Teams (JITs) which allowed investigators from one EU country to conduct investigations in another.
The European Investigation Order (EIO) which simplified procedures for obtaining evidence in other EU member states.

Faster police action

Alongside the EU developments, there were policing improvements under the Schengen Accord, where some EU member states, wishing to proceed more quickly, decided to remove all internal borders. It was thought that the absence of internal borders would require enhanced policing and judicial responses, which led to the creation of the Schengen Information System (SIS), a database containing details on individuals wanted under the EAW, details of immigrants refused visas, asylum seekers, stolen vehicles and other items. The Schengen Accords also allowed for cross-border police pursuits.

Initially, the United Kingdom chose not to participate in the Schengen Accords, preferring to retain passport and customs controls at borders. However, as the membership of the European Union grew and the capabilities of the SIS developed into the largest and most comprehensive police database in the world, now called SISII, the UK was allowed to opt into parts of the Schengen Accords. This included full access to SISII, integrating it into the UK’s Police National Computer (PNC).

Post-Brexit impact on criminal justice procedures

When the UK left the European Union in 2020, the trade and cooperation agreement (TCA) which set out the terms of our departure, excluded the UK from many of these policing initiatives, while allowing limited access to others.

A major loss for British police, border, and customs officers operating at British ports and airports was the exclusion from access to SISII, impairing their ability to check directly the European immigration status and criminal records of individuals presenting themselves at the border.

This was particularly relevant as Brexit, and the withdrawal of the UK from the Dublin agreement, which would have allowed the UK to return asylum seekers to the country in which they first claimed asylum. This would have been shown on SISII. The growth, since Brexit, in the numbers of asylum seekers arriving in the UK in small boats from France has been claimed to be linked to this.

Another significant loss to the UK was full membership of Europol, although the TCA permitted UK liaison officers to be posted there.

Britain’s rudimentary systems

In terms of judicial assistance, the UK lost access to the European Investigation Order. This meant that UK investigators making enquiries abroad, and EU MSs wishing enquiries to be made in the UK, have had to revert to the sending of ILoRs similar to the position prior to 1992. Owing to the lengthy bureaucracy required, this has impeded criminal investigations between the UK and other EU states.

Where once a UK police investigator could send an email to the Dutch police, and receive a reply within a few days, that officer now has to complete a full ILoR, which the Crown Prosecution Service, who are responsible for dealing with such things, has to translate into Dutch and forward to the Dutch Ministry of Justice. If the enquiry complies with Dutch law, the ministry will forward it to a Dutch investigating magistrate for action.

Difficulties in extradition

The UK retained partial access to the EAW, but under ‘Norway’ ‘surrender’ rules. This means that extradition requests between the UK and EU countries are now subject to additional conditions. It must be proved the crime is recognised as such in both countries, and provides that EU states may refuse extradition of their own nationals. In addition to this, ten EU member states have already signalled their intention to retain the right to refuse to extradite their own nationals to non-EU countries for trial. This, of course, includes the UK. The TLA allowed the UK to retain access to a passenger names database and to a system allowing members to query each other’s databases for matches for DNA, fingerprints and vehicle registrations. This latter system was known as the Prüm system after the German town where the agreement was signed. However, in the event of a ‘match’, at least two EU MSs require the UK to submit an ILoR to obtain the information they hold.

Broken promises

During the Brexit debate, promises were made, notably by Lord Gove, who said of post-Brexit police and security co-operation with the EU in a parliamentary debate in October 2020 that “there are many, many areas in which we can co-operate more effectively to safeguard our borders outside the European Union than we ever could inside”. Regrettably, he was not correct.

To bring us up to date, the UK/EU reset meeting on 19 May 2025 agreed on a security pact which included an intention to improve police and judicial cooperation. The UK hopes to be granted greater access to EU security databases, notably SISII, but nothing has been agreed yet, nor is this certain to happen. The agreement includes the establishment of “structured dialogues” to discuss the issues around better cooperation and strategy. Hopefully this will bring concrete benefits in the fullness of time.