Those who subject David Hicks to an unfair trial may breach international law, writes Geoffrey Robertson.

The term "Bush lawyer" is Australian slang for a hick counsellor, ignorant of the law. Thanks to recent decisions of the US Supreme Court and inquiries into torture at Abu Ghraib, it has been given a wider meaning, to denote the lawyers in US Government service who have misunderstood or misrepresented the fundamental rules of human rights in their advice to the President. Their mistakes have been so damaging that the British Attorney-General has taken to tendering his own advice to the White House about Guantanamo Bay - namely to close it. The case of David Hicks should provide his Australian counterpart with an opportunity to do likewise.

It is, let us remember, a war crime to commit a "grave breach" of the Geneva Convention. Article 8(2)(a)(vi) of the Rome Statute for the International Criminal Court, to which Australia (but not the US) is a party, defines such breaches to include "wilfully depriving a prisoner of war or other protected person of the right of fair and regular trial". The Supreme Court has now declared Hicks to be a person protected by the Geneva Convention, and there must come a point at which Australian law officers who wilfully authorise or approve an unfair and irregular trial of an Australian citizen become complicit in a grave breach of international law.

No doubt Australia's Attorney-General, Philip Ruddock, like the US President, has merely accepted the advice of the US Government lawyers that Guantanamo proceedings were lawful. From now on, that excuse will be unavailing. All the President's lawmen at first advised that Guantanamo was not on American soil, so due process did not apply. That argument was rejected by the Supreme Court in 2004. Next, they advised that the Geneva Convention did not protect the detainees because Afghanistan was a failed state or because they were not wearing military uniforms when captured or because the convention was "quaint" and "obsolete" or because the President as commander-in-chief could override them. Last month, the Supreme Court in the Hamdan case shredded these arguments as well. Were the Bush lawyers abashed? Not at all. One of them, Professor John Yoo, complained: "The court is attempting to suppress creative thinking."

He was one of the "creative thinkers" who approved interrogation techniques such as "waterboarding" (the process that mimics drowning) and "using detainees' individual phobias, such as fear of dogs". Other Bush lawyers approved interrogation techniques ranging from prolonged subjection to cacophonous noise to sexual humiliation and "other scenarios designed to convince the detainee that death is imminent for him and/or so for his family". This was not "torture", they advised, which required pain comparable "to physical injury such as organ failure, impairment of bodily functions or even death".

These "creative" techniques were used at Guantanamo when the base was assumed to be a Geneva-free environment, but the Schlesinger inquiry found that, once taught to military interrogators, they "migrated" with them to Abu Ghraib and other prisons in Iraq, where they were adapted by "sadists on the night shift". It is not clear whether David Hicks has been subjected to them but they have on any view produced an inhumane environment to which no one should be subjected, and certainly not for years on end.

Ruddock believes that Hicks should be tried - but for what, exactly? The US would be entitled to try him for a war crime but so far he has faced only a generalised charge of a conspiracy based on his presence in the ranks of those who fought for the Taliban, which was the de facto government of Afghanistan. It is not a crime to enlist in the army of a government - even a government as unpleasant as the Taliban - otherwise all soldiers on a losing side would be guilty and peace agreements would never be negotiated.

Since the Hamdan decision, Bush lawyers have been back at work drafting legislation for a new tribunal to replace the "special military commissions" - the sad little Star Chambers that were struck down by the Supreme Court. Their early drafts provide no reassurance that these replacement tribunals will secure "the rights of fair and regular trial". A trial cannot be regular if judges and jurors owe obedience to the detaining authority, and the draft legislation provides for trial by US army officers. They cannot be fair with procedures that still prevent the defence from challenging prosecution evidence and admit evidence obtained by torture. At common law, based on Magna Carta, a criminal process cannot be fair if it is delayed through no fault of the defendant for more than five years (the point at which, the Privy Council has held, any death sentence must be commuted). Inevitably, the new tribunal will be subject to Supreme Court challenge, which will take until 2008 to resolve. Hicks and other detainees cannot be faulted for challenging the fairness of the process.

The advent of new forms of terror and new forces to inflict it on the innocent challenges democratic societies to respond with legal processes that do not abandon our cherished values. In some respects, the American record is impressive: internal documents show how strenuously the attempts to evade Geneva protections were opposed internally by US military lawyers. They were denounced by bar associations and defeated - eventually - in the courts and (in the case of torture) by John McCain's work in Congress. But the process is lengthy and unpredictable.

The White House, on present indications, cannot bring itself to grant foreign detainees the "fair and regular trial" by juries in state courts, as afforded to US citizens, nor the court martials afforded to its own soldiers. Nor will it choose an acceptable alternative, such as trial by independent or by international judges.

Given Australia's obligations under the Geneva Convention and the Rome Statute, and the history of demonstrably erroneous advice that the White House has received on interrogation, due process and treatment of foreign prisoners in Guantanamo, it may be time for the Australian Attorney-General to stand up to the Bush lawyers. He could echo the advice of his British counterpart: not only is closure of Guantanamo right in principle, it is right because "the historic tradition of the US as a beacon of freedom, liberty and of justice deserves the removal of what has become a symbol of injustice".

Geoffrey Robertson, QC, is author of Crimes Against Humanity, published this month by Penguin. This is an edited extract from his Kenneth Myer lecture, delivered yesterday at the National Library of Australia.