Britain can extradite jailed radical Muslim preacher Abu Hamza and four other alleged terrorists to the United States, the European Court of Human Rights ruled on Tuesday.
The court found that the men's human rights would not be violated if they were extradited, but allowed a three-month stay for appeal.
The men claimed that conditions at the ADX supermax prison in Florence, Colorado -- used for people convicted of terrorism -- and possible multiple life sentences they face would be grossly disproportionate and amount to inhuman or degrading treatment.
The Strasbourg-based court said Mustafa Kamal Mustafa, as Abu Hamza is also known, and four others -- Babar Ahmad, Syed Tahla Ahsan, Adel Abdul Bary and Khaled Al-Fawwaz -- could be extradited.
It held that "conditions at ADX would not amount to ill-treatment".
Britain's interior minister Theresa May hailed the ruling as "a very important decision".
"These individuals have been accused of some very significant crimes," she told BBC television. "Every court in the UK felt it was right that they should be extradited."
The panel decided to adjourn the case of a sixth man, Haroon Rashid Aswat, and invited parties to submit information on his schizophrenia and how this would affect US judicial proceedings.
Abu Hamza, the former imam of the Finsbury Park mosque in north London, is wanted in the United States on charges including setting up an Al-Qaeda-style training camp for militants in the northwestern US state of Oregon.
He is also accused of having sent money and recruits to assist Afghanistan's Taliban and Al-Qaeda and helping a gang of kidnappers in Yemen who abducted a 16-strong party of Western tourists in 1998.
Hamza, who is in his mid-50s and has one eye and a hook for one hand, was jailed in Britain for seven years in 2006 for inciting followers to murder non-believers.
The court had previously halted the extradition of Egyptian-born Hamza and three of the other men to the United States, saying the case needed further examination.
It later found that, given US assurances, there was no real risk the men would either be designated as enemy combatants and be subject to the death penalty or subjected to extraordinary rendition.
"If the applicants were convicted as charged, the US authorities would be justified in considering them a significant security risk and in imposing strict limitations on their ability to communicate with the outside world," the court said.
"Besides, ADX inmates -- although confined to their cells for the vast majority of the time -- were provided with services and activities (such as) television, radio, newspapers, books, hobby and craft items, telephone calls, social visits, correspondence with families, group prayer which went beyond what was provided in most prisons in Europe."
Between 1999 and 2006 all six defendants were indicted on various terrorism charges in the United States.
Bary and Fawwaz were indicted, along with slain former Al-Qaeda chief Osama bin Laden and 20 others, for their alleged involvement in, or support for, the 1998 bombing of US embassies in Nairobi and Dar es Salaam.
Ahmad and Ahsan are accused of various felonies including providing support to terrorists and conspiracy to kill, kidnap, maim or injure persons or damage property in a foreign country.
Ahmad, 37, has been detained pending extradition since 2004, reportedly the longest a Briton has been detained without trial in modern times.
His father Ashfaq Ahmad called for his son to be allowed to go on trial in Britain immediately and said the family would appeal against the ruling.
"Babar is a British citizen accused of a crime said to have been committed in the UK, and all the evidence against him was gathered in this country," he told reporters in London.
"Nevertheless, British justice appears to have been subcontracted to the US. This should be immediately rectified by putting Babar on trial in the UK and ordering a full public inquiry."