WASHINGTON — When the CIA sought permission to use harsh interrogation methods on a captured al-Qaida operative, the response from Bush administration lawyers was encouraging, even clinical.

In one of several memos forming the legal underpinnings for brutal interrogation techniques, the CIA was told Abu Zubaydah could lawfully be placed in a box with an insect, kept awake for days at a time and slapped multiple times in the face. Waterboarding, too, was acceptable because it didn’t cause the lengthy mental anguish needed to meet the legal standard of torture, the 2002 Justice Department memo says.

The release last week of a Senate report cataloging years of such interrogation tactics has revived debate about legal opinions since discredited and withdrawn and about the decision to not prosecute the program’s architects or officers who used the methods. Civil rights groups in the United States and abroad are renewing calls to prosecute those who relied on techniques that President Barack Obama has called torture.

“How can we seriously use the phrase ‘rule of law’ if crimes of this magnitude go uninvestigated and unprosecuted?” said Jameel Jaffer, deputy legal director of the American Civil Liberties Union.

The Justice Department, which spent years looking into the matter, says it lacks sufficient evidence to convict anyone and found no new information in the report. It also is far from clear that any international case could be brought.