Anthony Scrivener: Sooner or later they will have to admit there is no evidence

Britain and America should give the Guantanamo prisoners back their rights

It seemed such a good idea at the time: President Bush at his decisive best, rounding up terrorists and putting them in no-man's-land in Cuba, safely away from the jurisdiction of the US courts. There they could be detained indefinitely without regard to the US Bill of Rights or the Constitution, or the Geneva Convention. They then could be tried by a bunch of American generals (military men do make wonderful judges once they have been taught the rudiments, as any retired communist or South American dictator could confirm). It looked like a real vote-catcher. But rather like starting a war for reasons which did not really exist, it was a turkey - and turkeys tend to come home to roost.

Leaving on one side the thrill of locking up agents from the "axis of evil", some rather obvious problems festering away beneath the surface were bound to erupt in time. President Bush has done well to keep those difficulties under wraps for so long; it is a pity for him that he could not keep them down until after the November election. The proposed release of the five British detainees is the first of many eruptions which promise to cause both the US and British governments acute embarrassment. The crucial question is whether the US government really is going to send a national of a friendly state to be tried by a military tribunal, which has the power to impose the death penalty, in defiance of all principles relating to human rights and international law. The US government has already decided that John Walker Lindh, a detained US citizen, should be tried by the courts rather than by the generals. Why should foreign nationals be dealt with differently? Is the US government going to alienate its allies by doggedly pursuing this course?

The problem becomes even more acute when, after the detainees have been caged up and manacled for two years in Guantanamo Bay, there is not even enough evidence to bring them before a military tribunal. Does Bush believe that all that is necessary for having made a ghastly mistake is an apology at the prison gates?

Allowing a British citizen to be "tried" by a US military tribunal would place the British government and Tony Blair, in particular, in an impossible position: so much for the special relationship and that congressional medal given to Mr Blair. It would mean that not only did we not even get a share of the construction contracts for Iraq - a country we helped to demolish - but that now our nationals were to be dealt with by our ally in contravention of all accepted civilised principles, despite our protests. The tired Labour backbenchers who have in the past been whipped or bribed by their leaders to swallow their principles and ignore manifesto promises in order to save Mr Blair, might at last break loose. All of this explains why Lord Goldsmith, the Attorney-General, has been so busy going to and from meetings with senior members of the US administration. It is now possible to interpret these events in the light of the proposed releases.

Lord Goldsmith no doubt explained the British government's political predicament to his US counterparts, who knew all about such problems - but they did not want to release the detainees without a guarantee that they would be charged with something. Just to release them would put the US government in a political predicament, by exposing the lack of any justification for having kept those men for so long.

So the Attorney-General and his team browsed through the so-called evidence against the British detainees. It would not have taken them too long to appreciate that evidence extracted from detainees under the Guantanamo Bay regime was unlikely to be accepted in British courts, not least because the procedures in the Police and Criminal Evidence Act were not followed. Given that the men were detained without a formal caution or legal representation, in conditions that breached the Geneva Convention, there must be a doubt as to whether the statements they made were voluntary.

There was then an interesting interlude when an attempt was made to avoid further embarrassment for the two governments. The Attorney-General returned from the US waving a piece of paper which contained a masterly US suggestion that if the detainees would plead guilty to something, the Bush government would promise that nothing too horrible would happen to them - a good old American plea bargain. If it was accepted, then everyone (except perhaps the detainees) would be tolerably happy. Unfortunately, the detainees declined to plead guilty to some offence they had not committed. They were not willing to throw themselves at the mercy of a military tribunal that had yet to be set up.

This left the only possibility: release the detainees into British custody. Politically, there has to be some police inquiry, to justify the long period of incarceration. The Foreign Secretary, Jack Straw, spoke from this position in the Commons on Thursday, asserting that there would be an investigation. Realistically, since any evidence gathered at Guantanamo Bay is inadmissible, the police would have to start from scratch in the hope that under sustained questioning the detainees would make some damning admission. But while Mr Straw was putting over the political party line, the Home Secretary, David Blunkett, rather gave the game away in a rare instance of frankness when he announced on television that: "No one who is returned in the announcement will actually be a threat to the security of the British people."

In one moment of enlightenment, he not only expressed the true practical position but also made himself a spokesman for the defence on any bail application to be made by the detainees on their return. His utterance promises to be the most quoted in criminal law this year. Of course, it is possible for the Government lawyers to say that Mr Blunkett did not realise what he was saying, and many would agree that there is abundant evidence from other past events that this is always a possibility.

The prognosis is that after a period of interrogation, the five detainees will be released with no greater penalty than being shadowed by MI5 agents in a variety of disguises. No doubt they will be approached by US plaintiff lawyers with an offer to sue the US government for wrongful detention on a no-win, no-fee basis.

There remains the problem of the other British subjects still being detained. As if all of this was not enough, President Bush faces yet another imminent problem: the Supreme Court is about to decide whether or not Guantanamo Bay falls within the jurisdiction of the US. The White House asserts that it does not, which means US law can be ignored. But there are legal grounds for contending that land lawfully owned, occupied and controlled by a state is, like an embassy, within its jurisdiction.

Underlying the stated positions of both governments with respect to persons like the Guantanamo detainees there lies a deep fallacy. To justify detention you need to have evidence. The non-existence of this evidence is not a justification for allowing a conviction without evidence on the say-so of some unidentified politician or state official, or on a lower standard of proof: it is only a justification for release and a verdict of not guilty. Sooner or later both governments will have to face up to this long-established principle. It is all part of the rule of law and helps to explain why we are a democracy.

Anthony Scrivener QC is a former chairman of the Bar Council