LONDON, Dec. 16 -- Britain's highest court of appeal struck a blow against the government's anti-terrorism policy Thursday by ruling it cannot detain suspected foreign terrorists indefinitely without trial.
In a stinging rebuke to Prime Minister Tony Blair's government, the panel ruled 8 to 1 that the provision authorizing the detentions violated European human rights laws and was discriminatory because it applied only to foreigners. Eleven suspects are being held under the policy, five of whom have been in custody for nearly three years.
"The real threat to the life of the nation, in the sense of a people living in accordance with its traditional laws and political values, comes not from terrorism but from laws such as these," wrote Leonard Hoffmann, one of the eight justices in the majority, referring to the anti-terrorism provision. "It is for Parliament to decide whether we will give terrorists such a victory."
The detainees, all Muslim men, were not released, because under British law, the last word on the legality of the anti-terrorism act belongs to Parliament. But legal observers said the ruling would force the government to amend the law, allowing the men to be either brought to trial or held under less restrictive conditions such as house arrest.
"It is ultimately for Parliament to decide whether and how we should amend the law," said Charles Clarke, Britain's new home secretary, in a statement. "Accordingly, I will not be . . . releasing the detainees, whom I have reason to believe are a significant threat to our security."
The decision was hailed as a triumph by civil libertarians, who have called the indefinite detentions "Britain's Guantanamo Bay."
"Internment has been a festering sore on our nation's conscience for nearly three years," said Shami Chakrabarti, director of Liberty, a London-based human rights group whose attorneys participated in the appeal. In a statement, she added: "By acting as judge, jury and jailer, the government has flouted the very values it claims to defend. It must now act honorably and charge or release all those currently held without delay."
But government supporters said the justices had underestimated the seriousness of the terrorist threat to Britain.
"It's all very well for the law lords in their ivory tower to talk about human rights, but I'd say the real threat comes from those who would do to Canary Wharf what terrorists did to the Twin Towers in New York or put poison in the London Underground," said Andrew Dismore, a member of Parliament from the ruling Labor Party, referring to the home of London's tallest buildings and its mass transit rail system.
One solution, Dismore suggested, would be for the government to amend the law to allow the introduction of wiretap evidence and testimony by concealed government witnesses in terrorism trials.
In response to the Sept. 11, 2001, attacks on New York and the Pentagon, Parliament adopted anti-terrorism legislation allowing for the detention and deportation of foreign nationals suspected of terrorism. In cases where suspects argued they could be tortured or killed if they were returned to their countries, the law allowed for indefinite imprisonment.
At the time, the government, citing the existence of a public emergency, formally removed itself from the requirement in the European Convention on Human Rights that all persons have the right to a fair trial. Britain was the only European country to take such action.
Of the nine men who brought the case that the justices ruled on Thursday, eight were detained in December 2001 and the ninth in February 2002. Two of the men have voluntarily left the country to escape detention, one has been freed, one released on bail and another transferred to a state-run mental institution.
Among those being held are Abu Qatada, a Jordanian cleric whom the government described as the spiritual inspiration for militant groups and terrorists, including the leaders of the Sept. 11 attacks. Another is Mahmoud Abu Rideh, a Palestinian whom the government accused of raising money for terrorist causes. The others have not been identified.
Attorneys for the detainees said half had shown signs of serious mental illness and one had attempted suicide. Government officials have insisted that the men, most of whom are held in a high-security prison in south London, have been properly treated and given regular access to relatives and attorneys.
All have received periodic hearings by a tribunal established under the law. But the panel has heard evidence from British intelligence services in secret, without the detainees or their attorneys present. In all but one case, the tribunal has upheld the detentions.
One of the detainees, identified as "A," said he welcomed Thursday's ruling. "I hope now that the government will act upon this decision, scrap this illegal 'law' and release me and the other internees to return to our families and loved ones," he said in a statement released by his attorney.
In their ruling, the justices argued that it made no sense for the government to claim that foreign nationals suspected of terrorism posed a more serious threat than British citizens, similarly suspected, who are not subject to indefinite detention. Some also questioned more broadly whether Britain faced an imminent danger from terrorism that justified the curtailment of liberties.
"Indefinite imprisonment without charge or trial is anathema in any country which observes the rule of law," concluded Justice Donald Nicholls. "It deprives the detained person of the protection a criminal trial is intended to afford."