Criminals should not be able to evade justice simply by slipping across a national boundary.

Common sense though that may be, many have tried. Thanks to the growing culture of cross-border co-operation between police forces and justice authorities in different EU countries, however, the majority find their "escape" is short lived. Since the introduction in 2004 of European arrest warrants, dozens of suspects have been brought back to Scotland from other European states to face justice, including Marek Harcar, who murdered 40-year-old sales executive Moira Jones in Glasgow in 2008.

No wonder, then, that senior Scottish police officers see the warrant as a vital tool of justice, and that along with Justice Secretary Kenny MacAskill, they are so concerned by Home Secretary Theresa May's threats to do away with it as part of an opt-out of a raft of EU police and justice co-operation agreements. It does Ms May little credit that the move has apparently been made as a sop to Tory eurosceptics. Complaints that too much money, police and court time in the UK has been taken up in the business of extraditing foreign nationals, sometimes over trivial offences (including, infamously, the theft of a wheelbarrow), do not invalidate the warrants. Where a country is issuing a great many warrants for its own citizens to be extradited, such as Poland, the first move for the Home Office should be to open a dialogue to see if the number can be brought down (to reduce Polish prisoners absconding from the country while on day release, for example). Other countries, including Germany, have sought to set their own standards on which warrants to execute. Such measures should certainly be considered before the abolition of a system which is basically working well.

The last thing Scottish police officers want is a reversal of the trend of growing cross-border co-operation between EU police forces. European arrest warrants have been instrumental in tackling Scottish gangsters residing in Spain who once saw themselves as untouchable. Last week, the assistant chief constable of Lothian and Borders Police called for closer links between British and Irish police and for consideration of a new law forcing foreign sex offenders to reveal their convictions on entering the UK (a suggestion endorsed by the Scottish Conservatives). Co-operation is working; now is not the time to apply the brakes.

What of other ways in which co-operation could be impeded by the opt out? What about sharing research and information? What about joint efforts to manage immigration? Assuming Britain could subsequently opt back in to those areas of co-operation it liked and dump those it didn't, is a risky game. Having to negotiate dozens of separate multilateral or bilateral treaties and agreements to achieve the same level of co-operation as Britain already enjoys, would be tortuous at best.

Whether throwing this juicy morsel to their increasingly restive eurosceptic wing will help the Conservatives see off the threat from Ukip, remains to be seen. Whatever the reaction of her own party, Ms May has opened herself to the charge in Scotland of allowing internal Tory politics to trump the administration of justice. If there are problems with the way warrants are working, they should be reviewed, but abolition is not the answer.