Ukip leader Nigel Farage believes David Cameron should match his words with action and allow Britain to regain control of its extradition processes.
he said: "Out of the ashes of his third place in the European elections, a new and stoutly Eurosceptic David Cameron appears to have emerged. The European Union must stop interfering so much in our national life, he says.
"He has branded it “too big, too bossy and too interfering”, and insists that the Brussels establishment must wake up to the message sent to it by voters.
"Well, an opportunity has arisen for the Prime Minister to show he is serious when he says his guiding principle is “nation states wherever possible and Europe only where necessary”.
"For Britain is currently negotiating with the EU over whether to opt back into dozens of justice and home affairs measures that are being turned into European competencies under the Lisbon Treaty.
"We could stay out of them all. That would, after all, tally with the Cameron principle of “nation states wherever possible”.
"But it seems that instead, the Prime Minister is going to hand control to the EU permanently in 35 areas, the most notable of which is the European Arrest Warrant (EAW). It was under this warrant, remember, that Andrew Symeou was held in a Greek prison for four years before being cleared of involvement in a killing outside a nightclub.
"There is nothing necessary about allowing the EU to acquire the power to extradite British citizens on demand. Opting back in will mean the European Public Prosecutor gains the power to instruct national judges to issue arrest warrants. Extradition will become automatic, on the say-so of this all-powerful figure.
"This country has been managing extradition processes with other countries for centuries. Our courts have largely proved adept at balancing the rights of British citizens with the rights of foreign jurisdictions to uphold law and order.
"Extradition applications have been looked at on their merits, and the strength of the case weighed in the balance, without the automaticity of the EAW.
"This still works well in respect of many countries across the world: one thinks of the extradition of Shrien Dewani to South Africa last month to stand trial on a murder charge.
"That kind of extradition process respects national sovereignty, and is an example of independent nation states cooperating to their mutual benefit. But the EAW is a very different animal indeed.
"It hands over legal sovereignty to the European Union. It is more like rendition than extradition. No prima facie evidence is required, and national judges have almost no discretion so long as the paperwork is in order.
"In many of the inquisitorial legal systems on continental Europe, the consequences of extradition can involve being held in custody for questioning for years at a time.
"In a rational world, one would expect liberal opinion to be up in arms about this idea. But because it is about surrendering national sovereignty to Brussels, there is barely a squeak. Indeed, Nick Clegg is a particular cheerleader for the EAW, and championed it in his televised debates with me in March and April.
"The main reason he cited for submitting to the EAW was the need for a shared anti-terrorist effort.
"But in reality, the warrant is increasingly being deployed in much more mundane cases. Britons of good character are learning, to their utter incredulity, that they can be carted off at the flick of a pen.
"This hardly accords with the British legal tradition of “innocent until proven guilty”.
"I have never been soft on crime, and never will be. But our legal system evolved to include an extradition process that protected the ancient legal rights of individuals against the state, long before anyone thought of the EU, let alone the EAW. Our justice system is deeply embedded in our society and culture – and for all its faults, still commands a basic level of respect and assent.
"Being in charge of your own legal affairs is a basic signifier of a nation. If you don’t have it, then you are just an imperial outpost. So if Mr Cameron is remotely serious about his mission to defend Britain’s sovereignty, he should not be opting into the EAW – or a raft of other EU home affairs and justice measures.
This is the first big test of Mr Cameron’s new-found Eurosceptic backbone."
I would like to think he will pass it. But observing the behaviour of every Tory leader since Margaret Thatcher leads me to doubt that profoundly.
The European election results have shown that the British people have had enough of the salami-slicing of their sovereignty.
Far be it from me to advise Mr Cameron on how to re-engage with Eurosceptic opinion, let alone to restore some of his lost credibility. But if he falls at the first hurdle, he will certainly confirm the widespread view that the Conservatives are a lost cause for Eurosceptics.
That would be a gain for my party, Ukip, but a loss for my nation. I find myself hoping against hope that the Prime Minister will surprise me on this score.