More than 600 people languish in what a senior British judge has described as a "legal black hole" whose status the US Supreme Court is due to consider in June.
But before that, about 135 British parliamentarians have joined forces on Wednesday to file an appeal with the American court on behalf of 16 mostly British and Kuwaiti detainees.
"There's an issue of human rights here," said Former Foreign Secretary Robin Cook, one of 85 elected MPs and 50 peers from the House of Lords filing the petition.
He told Aljazeera.net on Saturday the British politicians' appeal aimed at encouraging the Supreme Court to ensure the inmates underwent proper legal process in the US, though "we would wish the detainees would be repatriated to Britain".
A UK lawyer who represents British detainee Firoz Abassi and is familiar with the appeal says the US must end the captives' legal limbo.
Louise Christian (R) with British
detainee Firoz Abassi's mother
"This is not about emotions, this is about international law," Louise Christian told Aljazeera.net."
"Either they should be treated as prisoners of war, who mustn't be questioned, and must either be released at the end of hostilities, or should be prosecuted for war crimes – or if they are connected to terrorism, they should be charged and prosecuted."
But the Guantanamo inmates have no idea of the arguments swirling around them because, as Christian points out, their correspondence with their families are censored and no mention of any legal process or challenge is allowed.
US President George Bush has characterised the captives as "bad people" and illegal combatants, while Defence Secretary Donald Rumsfeld branded them "hard core, well trained terrorists".
The detentions are justified says
US Defence Secretary Rumsfeld
But according to US-based Human Rights Watch, these blanket characterisations disguise what is already known about many of the detainees.
Dozens of known non-combatants have been jailed after anti-Taliban forces in Afghanistan swept up civilians in a wide net in exchange for bounty payments.
These include farmers, taxi drivers and others with no ties to al-Qaida or the Taliban. Some have been released after apparently meaningless detention. A few of those released after a year or more in custody were in their eighties.
A London lawyer monitoring the Guantanamo situation, Makboul Javaid, says Bush and Rumsfeld's controversial comments are likely to prejudice any trial the inmates may face later.
"There's a very great danger they would not face a fair trial," he told Aljazeera.net, "especially as those comments were well publicised and made by such high profile people.
Human Rights Watch also says at least three children between 13 and 15 years of age have been held for more than a year at Guantanamo, where an uncertain number of 16 and 17-year-olds are also jailed alongside adults – in contravention of international law.
"They should be released - they're children," said Javaid. "They should be handed back to their countries of origin and rehabilitated."