The order by U.S. District Judge Jeffrey White of San Francisco is the first time a government lawyer has been held potentially liable for the abuse of detainees.
White refused to dismiss Jose Padilla's lawsuit against former senior Justice Department official John Yoo on Friday.
Yoo wrote memos on interrogation, detention and presidential powers for the department's Office of Legal Counsel from 2001 to 2003.
Padilla, 38, is serving a 17-year sentence on terror charges. He claims he was tortured while being held nearly four years as a suspected terrorist.
White ruled Padilla may be able to prove that Yoo's memos "set in motion a series of events that resulted in the deprivation of Padilla's constitutional rights."
"Like any other government official, government lawyers are responsible for the foreseeable consequences of their conduct," wrote White, a Bush appointee.
Yoo did not return telephone and e-mail messages Saturday.
White ruled that Yoo, now a University of California at Berkeley law professor, went beyond the normal role of an attorney when he helped write the Bush administration's detention and torture policies, then drafted legal opinions to justify those policies.
Yoo's recently released 2001 memo advised that the military could use "any means necessary" to hold terror suspects.
A 2002 memo to then-White House Counsel Alberto Gonzales advised that treatment of suspected terrorists was torture only if it caused pain levels equivalent to "organ failure, impairment of bodily function or even death."
Yoo also advised that the president might have the constitutional power to allow torturing enemy combatants.
"The issues raised by this case embody that ... tension - between the requirements of war and the defense of the very freedoms that war seeks to protect," White wrote in his 42-page decision. "This lawsuit poses the question addressed by our founding fathers about how to strike the proper balance of fighting a war against terror, at home and abroad, and fighting a war using tactics of terror."
The ruling rejected the government's arguments that the courts are barred from examining top-level administration decisions in wartime, or that airing "allegations of unconstitutional treatment of an American citizen on American soil" would damage national security or foreign relations.
The Justice Department is representing Yoo and has argued for dismissing the lawsuit. The department has not said if it will appeal White's ruling. The department's on-duty spokesman, Dean Boyd, did not return a telephone message Saturday.
"It's a really a significant victory for accountability and our constitutional system of checks and balances," said Tahlia Townsend, an attorney with the Lowenstein International Human Rights Clinic at Yale Law School who represented Padilla.
White ruled that "the treatment we allege does violate the Constitution and John Yoo should have known that," Townsend said Saturday. "This is the first time there's been this sort of ruling."
Padilla is an American citizen who was arrested in Chicago in 2002 and accused of conspiring with al Qaeda to detonate a radioactive "dirty bomb."
He was held in a Navy brig in Charleston, S.C., for three years and eight months as an enemy combatant. Padilla's lawsuit alleges Yoo personally approved his time and treatment in the brig.
His lawsuit alleges he was illegally detained and was subjected to sleep deprivation, temperature extremes, painful stress positions, and extended periods of bright lights and total darkness. Padilla also alleges he endured threats that he would be killed, that his family would be harmed, and that he would be transferred to another country to be tortured.
He eventually was charged in an unrelated conspiracy to funnel money and supplies to Islamic extremist groups. Padilla was convicted in 2007 in Miami federal court, and is appealing.
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By Associated Press Writer Don Thompson