The Justice Department memo, dated March 14, 2003, outlines legal justification for military interrogators to use harsh tactics against al Qaeda and Taliban detainees overseas - so long as they did not specifically intend to torture their captors.
Even so, the memo noted, the president's wartime power as commander in chief would not be limited by the U.N. treaties against torture.
"Our previous opinions make clear that customary international law is not federal law and that the president is free to override it at his discretion," said the memo written by John Yoo, who was then deputy assistant attorney general for the Office of Legal Counsel.
The memo also offered a defense in case any interrogator was charged with violating U.S. or international laws.
"Finally, even if the criminal prohibitions outlined above applied, and an interrogation method might violate those prohibitions, necessity or self-defense could provide justifications for any criminal liability," the memo concluded.
The memo was rescinded in December 2003, a mere nine months after Yoo sent it to the Pentagon's top lawyer, William J. Haynes. Though its existence has been known for years, its release Tuesday marked the first time its contents in full have been made public.
Haynes, the Defense Department's longest-serving general counsel, resigned in late February to return to the private sector. He has been hotly criticized for his role in crafting Bush administration policies for detaining and trying suspected terrorists that some argue led to prisoner abuses at the detention center in Guantanamo Bay, Cuba.
Yoo's memo became part of a debate among the Pentagon's civilian and military leaders about what interrogation tactics to allow at overseas facilities and whether U.S. troops might face legal problems domestically or in international courts.
Also of concern was whether techniques used by U.S. interrogators might someday be used as justification for harsh treatment of Americans captured by opposing forces.
The Justice Department has opened an internal investigation into whether its top officials improperly authorized or reviewed the CIA's use of waterboarding, which simulates drowning, when interrogating terror suspects. It was unclear whether the Yoo memo, which focuses only on military interrogators, will be part of that inquiry.
The Justice Department repeatedly rebuffed demands for its release, but the ACLU prevailed in its FOIA litigation in getting the memos, reports CBS News Justice Department producer Stephanie Lambidakis.
The document also was turned over to lawmakers.
Justice Department spokesman Brian Roehrkasse said its release "represents an accommodation of Congress' oversight interest in the area of wartime interrogations."
Jameel Jaffer, director of the ACLU's national security project, said Yoo's legal reasoning puts "literally no limit at all to the kinds of interrogation methods that the president can authorize."
"The whole point of the memo is obviously to nullify every possible legal restraint on the president's wartime authority," Jaffer said. "The memo was meant to allow torture, and that's exactly what it did."
The 81-page legal analysis largely centers on whether interrogators can be held responsible for torture if torture is not the intent of the questioning. And it defines torture as the intended sum of a variety of acts, which could include acid scalding, severe mental pain and suffering, threat of imminent death and physical pain resulting in impaired body functions, organ failure or death.
The "definition of torture must be read as a sum of these component parts," the memo said.
The memo also includes past legal defenses of interrogations that Yoo wrote are not considered torture, such as sleep deprivation, hooding detainees and "frog crouching," which forces prisoners to crouch while standing on the tips of their toes.
"This standard permits some physical contact," the memo said. "Employing a shove or slap as part of an interrogation would not run afoul of this standard."
The memo concludes that foreign enemy combatants held overseas do not have defendants' rights or protections from cruel and unusual punishment that U.S. citizens have under the Constitution. It also says that Congress "cannot interfere with the president's exercise of his authority as commander in chief to control the conduct of operations during a war."
Senate Judiciary Committee Chairman Patrick Leahy said the memo "reflects the expansive view of executive power that has been the hallmark of this administration." He called for its release four months ago.
"It is no wonder that this memo ... could not withstand scrutiny and had to be withdrawn," said Leahy, D-Vt. "This memo seeks to find ways to avoid legal restrictions and accountability on torture and threatens our country's status as a beacon of human rights around the world."