In the Mail on Sunday, James Forsyth reports that Spain is the latest EU member to cause David Cameron some trouble:

‘Spain is blocking Britain’s efforts to opt back in to the European Arrest Warrant, which controls the extradition of criminal suspects between EU member states.  For Britain to opt back in, all other states have to agree. But the Government suspects the Spanish will try to put pressure on Britain to offer concessions over Gibraltar. Those close to Cameron are emphatic that the British position will not change.’

For the Prime Minister, it’s another uncomfortable reminder that the EU is not always in practice the friendly family it purports to be – following shortly after the Juncker vote, in which our supposed influence failed to attend.

I’m sure James is right to rule out the prospect of concessions over Gibraltar – the Rock is rightly, justly and happily British, and will remain so.

The question, therefore, is what happens when Spain’s attempts to extort concessions are rebuffed. There’s the distinct possibility, of course, that their sabre-rattling will die away, replaced by a discreet retreat. But if they were to stick to their guns, and effectively veto Britain’s entry into the European Arrest Warrant? What then?

Well, if you’re a believer in what were once the basic principles of British justice, being unable to rejoin the EAW system would be no bad thing. The idea of extraditing UK citizens for offences that we do not in this country regard as crimes, or extraditing people based on an application form, rather than a British court hearing of the evidence on which the extradition is sought, has always been deeply troubling in principle. For victims of the unjust system such as Andrew Symeou, it has been deeply troubling in practice, too.

The fact that successive Conservative leaders as well as their Labour and Lib Dem opponents have gone along with such a system for so long is down to a willingness to trade fundamental principles for short-term political comfort. They fear – often accurately, I’m sad to say – that the electorate will reward security over freedom, and are unwilling to sacrifice some votes for something more important than poll ratings.

For that reason, we should expect to see a diplomatic charm offensive to secure Britain’s re-entry into the system, despite the fact that scores of MPs will be hoping we don’t secure it.

The electoral impact of a failure to rejoin the EAW would likely be two-fold.

In the short term, it would undoubtedly be painful for Cameron to start 2015 with Miliband and Clegg accusing him of losing a route to swiftly extradite criminals suspects from abroad, while UKIP would use the scenario as proof that we have no clout in the EU. Avoiding a backbench rebellion over the decision to opt back in to the system would only be limited compensation for another public demonstration of the degree to which Cameron’s negotiating partners view the UK with disdain.

In the longer term, it would be an unintended boon to the Better Off Out campaign – the EAW is one of the few aspects of EU membership which can play well with the electorate, so its removal from the scene would leave the In campaign’s cupboard looking rather bare come the 2017 referendum. But I doubt that would offer the Prime Minister any cheer, either.