As a row rages over the rights of prisoners at the US detention centre at Guantanamo Bay, Cuba, the BBC News website examines the different legal processes the US military has put in place to try them.
As of 16 February 2006 there were about 490 detainees at Guantanamo Bay. Since its inception in January 2002, some 267 people have been transferred or released from the camp, the Pentagon says.
What are Combatant Status Review Tribunals?
These were a mechanism instituted by the US military in which Guantanamo detainees could challenge the rules under which they were being held and their designation as "enemy combatants".
Officials say most inmates reacted "positively" to the status reviews
Every prisoner held at Guantanamo Bay was assessed under CSRTs held between August 2004 and March 2005. Of the 558 cases assessed, 520 were held to be "enemy combatants" and 38 people as "non-enemy combatants". The CSRT process will be applied to any new prisoner at the camp.
The hearings were controversial not least because the detainees were not allowed access to lawyers. Nor could they hear classified material that might have formed part of the evidence against them. Rights groups - and the United Nations - say hearings set up by the military violate prisoners' rights to challenge the legality of their detention before a judicial body.
Why were CSRTs held?
The US Government designated the prisoners - accused of having links to Afghanistan's ousted Taleban regime or al-Qaeda - as "enemy combatants", not lawful members of a national army who would have been considered prisoners of war, protected under the Geneva Conventions and released at the end of hostilities.
It said that as unlawful "enemy combatants", the men could be held indefinitely even if not charged. And as they were held in a camp built on territory leased from Cuba, the US government also argued that civilian courts had no jurisdiction because they were not in sovereign US territory.
Those assumptions were challenged through the legal system by some detainees. The US Supreme Court ruled in July 2004 that civilian courts did have the right to consider challenges to the legality of foreign nationals captured abroad and held at Guantanamo Bay.
Although the military base is on rented land, the US had "complete jurisdiction and control" at Guantanamo Bay and therefore the courts had jurisdiction, a majority of the judges decided.
The US government then announced there would be military commissions to review the status of detainees, in a move correspondents say was designed to pre-empt matters coming before civilian judges.
What are military commissions?
The US deems that military commissions are the appropriate way to try the men it believes are "enemy combatants". It says such military commissions have historically been used to try violations of the law of armed conflict and related offences.
The commissions involve a panel of military judges, with military prosecutors and defenders. Defendants may also hire their own civilian defence counsel, though some aspects of the trial may be held in secret and the accused may not hear all the evidence against them.
The US insists there will be a presumption of innocence for the defendants, who may only be convicted if their guilt is proved beyond reasonable doubt. The accused may present evidence and call witnesses, and their case will not be considered more harshly if they refuse to testify.
An appeal will also be allowed, but critics say there is still not enough independent oversight of the process.
How many people have gone through the commissions?
Currently some 14 prisoners have been deemed eligible for hearings under the commissions, and of those 10 have had charges against them approved by President George W Bush. Trial proceedings have begun against five individuals and are at various stages - several have been stayed.
The Pentagon says it is a "misconception" to think that every prisoner at Guantanamo Bay is due a trial by military commission. It sees the main purpose of the camp as stopping "enemy combatants" returning to the field of combat, although there is dispute over whether many of those held are actually combatants.
What of cases in the civil courts?
The Pentagon says more than 200 current detainees at Guantanamo Bay have filed habeas corpus petitions in the US courts - effectively asking the courts to determine whether they are being legally held.
There have been a series of conflicting legal judgments on Guantanamo Bay in the federal courts and all eyes are on a forthcoming case before the US Supreme Court.
Salim Ahmed Hamdan, a Yemeni who was formerly a driver for Osama Bin Laden, has questioned the legality of his detention and a scheduled trial by special military tribunal. The court heard oral arguments earlier this year and is due to give its judgment by the end of June.
The administration argues that recently adopted legislation severely limits detainees held at Guantanamo from challenging their detention in US courts. The legislation, the Detainee Treatment Act, banned the torture of detainees but also included an amendment applying to inmates held at Guantanamo Bay.
What will happen to the prisoners?
Those who go through the military tribunals and are convicted will be sentenced by the military justice system. The death penalty is an option, but officials have already said that they will not seek such a punishment in at least three of the cases set for trial.
Detainees judged to no longer pose a threat, or against whom there is insufficient evidence that they committed war crimes, or who can provide no fresh intelligence to investigators, are returned to their home countries. Others are sent back for their own nations to decide whether they should face legal action.
Five men who were returned to Britain were questioned but then released without charge. But in France, four men sent back from Cuba were remanded in custody while they were investigated for possible links to terrorist organisations.
All "enemy combatants" detained at Guantanamo Bay - except those who are pending trial by military commissions - are eligible for an annual review of their status.