The Pentagon and US military prosecutors were quick to hail the verdict on Salim Hamdan, the first Guantanamo detainee to be tried by the special military tribunal. They insisted that his acquittal on conspiracy charges and the light sentence passed on him for supporting terrorism in his role as Osama bin Laden's driver showed that “as a whole the process worked”.

Few others would agree. The outcome is an extraordinary rebuff for the Bush Administration, which saw this as a test case and had asked for a 30-year prison term. The verdict by a jury of six military officers, chosen by the Pentagon, does nothing to settle doubts about the legiti- macy of the tribunals themselves, set up as an alternative to a federal court or the regular military justice system. Nor does it ensure that the other 19 detainees due to be prosecuted will have their rights protected. As Colonel Steven David, Hamdan's defence counsel, said afterwards, the trial was marked by the acceptance of hearsay evidence and secret testimony, restrictions on media coverage and allegations of abusive interrogations. It was time, he said, to scrap this “mess”.

The Bush Administration agreed to this first trial only after pressure from the American Bar Association, appeals to the Supreme Court, international protests and growing disquiet within the United States at the limbo status of the remaining 270 detainees in Guantanamo.

Administration officials insisted that the tribunals were the best way to protect sensitive intelligence information. But US lawyers have questioned the legitimacy of trying anyone under a procedure not set up until five years after they were detained. Others have said that the trial violated two fundamental principles of criminal justice: the ban on coerced evidence and the prohibition on retroactive criminal law.

What is more shocking than any of these legal doubts, however, is the reaction of the Bush Administration. Having spent five years in pretrial detention, Hamdan now has only five months more of his sentence to serve. But the Pentagon has now declared that he would not be freed, but could be held indefinitely as an “unlawful enemy combatant” after finishing his sentence.

This remark is as outrageous as it is unprincipled. As a US navy lawyer who first represented Hamdan said: “If he simply goes back to the same cell, why did we all come down here?” The Pentagon stance appears motivated by defiance and anger at the verdict. As even the most hardline Administration officials must recognise, Guantanamo has inflicted huge damage on America's reputation around the world, undermining the faith of its friends in US justice and giving America's critics a propaganda gift. If the Pentagon now believes that it can override the verdict of the very courts it has set up, it mocks any pretence of a fair trial.

The Pentagon also appears to be out of step with political realities. Both presidential candidates have said that they would close the detention centre in Guantanamo. It is inconceivable that either would agree to the continued and indefinite detention of a man who has already received a fixed sentence. George Bush's presidency has only five months to run. During that time he should himself close the camp, charge or release the remaining detainees and expunge this legal stain on his Administration's record.