FOR police officers, the logic is easy: If criminals can cross borders, so should they.

Scottish law enforcement agencies and prosecutors increasingly talk of a new spirit of co-operation with their European counterparts in recent years.

Detectives from forces such as Strathclyde and the Scottish Crime and Drug Enforcement Agency, for example, have had major success working with their colleagues in Spain to root out Clydeside gangsters hiding on the Costa del Crime.

That has been followed up by a new wave of joint work by prosecutors to seize or freeze the assets of Scottish criminals overseas.

Officers insist that spirit of co-operation – and the drive to locate criminals such as, currently, a suspected killer of Glasgow gangland enforcer Kevin "The Gerbil" Carroll – will not be stopped. That spirit has been reciprocated. Foreigners detained on behalf of overseas police include Benat Atorrasagasti Ordonez, a suspected Basque terrorist seized under a Eurowarrant in July after he was found in Edinburgh.

However, officers are worried it could be jeopardised by Theresa May as the Home Secretary signals the UK will opt-out of a series of EU justice deals, including European Arrest Warrants.

David O'Connor, president of the Association of Scottish Police Superintendents, last night said such warrants were "no doubt important in preventing, detecting and disrupting criminal activity across borders and bringing alleged offenders to justice".

He added: "The removal of such a power could have a detrimental effect on [policing] national threats such as terrorism, money laundering, people trafficking, international sex offending and internet-related crime. The police need these international powers and the European Arrest Warrant has been used successfully. So why would we withdraw from such co-operation between countries and crime-fighting agencies?"

Such practical concerns are acknowledged by Tory Eurosceptics. But today they set out what they see as a democratic case that outweighs police pragmatism.

In a report published today, Conservative MP Dominic Raab found 60 of the 135 EU justice laws cemented in the 2009 Lisbon Treaty had "some practical law-enforcement value". However, he added that none merited giving up democratic control to supranational EU institutions.

Mr Raab believes the Lisbon Treaty effectively cedes democratic control from Britain to the European Commission and the European Court of Justice.

Mr Raab's report rejects claims that opting out of the Eurowarrants would leave the UK unable to secure the return of suspects like 21/7 bomber Osman Hussein, who fled to Italy.

It was "perverse", his report argued, to suggest Britain cannot co-operate bilaterally with European partners on counter-terrorism or crime without sacrificing basic principles of justice.

Ms May said Eurowarrants had had "some success in streamlining the extradition process within the EU". She added: "But there have also been problems. There are concerns in particular about the disproportionate use of the EAW for trivial offences, and for actions that are not considered to be crimes in the UK."

She has until June 2014 to opt-out of Lisbon, perhaps after first negotiating something to replace the Eurowarrant system.

Mr Raab, meanwhile, insisted police could co-operate more across borders, including on criminal records.

Last week The Herald reported demands for a EU-wide system for monitoring sex offenders after several convicted figures were able to move to Scotland without revealing their past crimes.

Marek Harcar – the killer of Moira Jones in 2008 – was one of those criminals.

Last night Beatrice Jones – Moira's mother – urged Ms May not to go ahead with her opt-outs on justice. She said: "It shows total disregard for victims everywhere."