A federal judge on Monday ordered the Pentagon to release a long-held Mauritanian captive at Guantánamo Bay who was once considered such a high-value detainee that former Secretary of Defense Donald Rumsfeld designated him for "special interrogation techniques."

U.S. District Judge James Robertson's ruling was classified, so there was no immediate explanation for why he granted the habeas corpus petition of Mohamedou Slahi, 39. A notation in court files said an unclassified version of the ruling would be made available, but didn't say when.

Slahi is the 34th Guantánamo detainee ordered freed since the U.S. Supreme Court ruled detainees could challenge their incarceration in federal court, but his name was already well known because of investigations into detainee abuse.

Those probes found Slahi had been subjected to sleep deprivation, exposed to extremes of heat and cold, moved around the base blindfolded, and at one point taken into the bay on a boat and threatened with death. Investigators also found interrogators had told him they would arrest his mother and have her jailed as the only female detainee at Guantánamo if he did not cooperate.

The interrogations were so abusive a highly regarded Pentagon lawyer, Marine Lt. Col. Stuart Couch, quit the case five years ago rather than prosecute him at the Bush administration's first effort to stage military commissions.

"He's been incarcerated, tortured and interrogated and rendered illegally," said attorney Nancy Hollander of Albuquerque, N.M., who represents Slahi free of charge. "After almost 10 years the government has not been able to meet the minimal burden to detain him that's required under habeas. He should be free."

Justice Department spokesman Dean Boyd said lawyers were "reviewing the ruling." The government has appealed some of the habeas release orders.

Slahi faces no criminal charges. He arrived at Guantánamo in August 2002, nearly a year after he turned himself in for questioning in his native Mauritania in late September 2001 and found himself handed over first to Jordan for interrogation and then to U.S. forces in Afghanistan.

He filed his petition for habeas corpus himself in handwritten English on March 3, 2005, on a form provided by prison camp staff.

It was Robertson's second Guantánamo habeas ruling. Earlier, he had upheld the detention of Yemeni Adham Awad, even though the government's case was "gossamer thin."

Robertson, a former U.S. Navy officer, has had oversight of Guantánamo cases for years. In 2004 he ruled the Bush administration's first attempt to stage military commissions was unconstitutional in the case of Osama bin Laden's driver, Salim Hamdan. Hamdan's case led to a Supreme Court ruling that the Bush administration had exceeded its authority in setting up the commissions. Hamdan was later convicted of supporting a terrorist organization before a military commission. He was released after serving an additional five months and is now free in Yemen.

Slahi had long been a person of interest to U.S. authorities investigating al Qaeda attacks and attempts in the United States, in part because he had lived as a student in both Germany and Canada in the 1990s.

Pentagon records said the military suspected him of ties to the Hamburg, Germany, cell that had carried out the Sept. 11, 2001 hijackings, apparently because accused 9/11 plotter Ramzi bin al Shibh named him during secret CIA interrogations.

U.S. officials also wondered whether he was linked to the failed al Qaeda Millennium Plot to blow up Los Angeles International Airport on Dec. 31, 1999.

According to both Pentagon and Senate investigations, Defense Secretary Rumsfeld gave permission for Slahi to be subjected to so-called "special interrogation plans" in August 2003, a year after Slahi had arrived at Guantánamo.

Slahi accused military authorities of having tortured him when he was brought before a military panel assessing the evidence against him in December 2005. He called the evidence against him illogical.

"It does not make any sense to me," he said, according to a Pentagon transcript. "It looks like O.J. trial."

In November 2006 he wrote his lawyers that he had denied any wrongdoing while in custody until he was tortured. "I yess-ed every accusation my interrogators made," after they tortured him, he said. "I even wrote the infamous confession about me planning to hit the CN Tower in Toronto."

He also made light of his attorneys request to list the number of times he was interrogated since his capture. "That's like asking Charlie Sheen how many women he dated."

As of Monday, he was unaware of the decision. His attorneys had asked to speak to him at the prison by telephone as soon as possible and asked the Pentagon to waive the 10-day advance notice for such a call.