The indefinite detention without trial of foreign nationals under emergency terror laws in Britain is incompatible with European human rights laws, Britain's highest court ruled today.
The decision, which comes as a final blow to former home secretary David Blunkett, throws the British government's anti-terror regime into chaos.
Nine men are being held under the controversial Anti-Terrorism, Crime and Security Act - introduced by Mr Blunkett in response to the September 11th, 2001, attacks on New York and Washington.
They took their cases to the House of Lords after the Court of Appeal backed the Home Office's powers to detain them without limit or charge.
A specially convened committee of nine Law Lords - who ruled 8-1 in favour of the detainees - had heard argument that detaining people indefinitely on suspicion alone contravened democratic rights and international obligations.
Kate Allen, director of Amnesty International UK
Solicitor Gareth Peirce, who represents eight of the detainees whose appeals were before the Law Lords today, said the British government had to act swiftly in the wake of the ruling.
"It will provoke an enormous constitutional crisis if the government fail to act swiftly," she said. "The government has to take steps to withdraw the legislation and release the detainees.
"There is no escape route for the Government, no escape route whatsoever. If there is no swift action from the government then the detainees could ask the European Court of Human Rights to be involved, but we trust that will not be necessary.
"It would be unconstitutional for the Government to hold out against such a strong judgment, such a very strong judgment."
Ms Peirce claimed that the detention had driven four of the detainees to "madness". She said a further four had had their mental health seriously affected.
Kate Allen, the director of Amnesty International UK, said: "We hugely welcome this ruling today. Morally, legally, a very clear message has been sent to the government.
"We are very hopeful that the new home secretary will take the opportunity to ensure that human rights are firmly back on the agenda."