The Wall Street Journal says the secret memo also concluded the Justice Department could not prosecute U.S. agents who broke torture laws.
"In order to respect the president's inherent constitutional authority to manage a military campaign ... (the prohibition against torture) must be construed as inapplicable to interrogations undertaken pursuant to his commander-in chief authority," read a March 6, 2003 draft of the report obtained by the Journal.
News of the memo comes amid several investigations into the abuse — sometimes resulting in death — of U.S. detainees in Iraq and Afghanistan.
While seven low-ranking soldiers are charged with crimes in the most publicized cases that occurred at the Abu Ghraib prison in Baghdad, there are questions about accountability up the chain of command.
Some of those questions concern military commanders, like Gen. Geoffrey Miller, who recommended in the summer of 2003 that prison guards help "set the conditions" for interrogating prisoners. Lt. Gen. Ricardo Sanchez, the U.S. commander in Iraq, was given power to approve techniques like sleep deprivation and stress positions.
But other questions regard civilian authorities. Athat depicted some Geneva Convention rules as obsolete has already come under scrutiny.
The report uncovered by the Journal frames more questions. It was not clear if President Bush ever saw the report on his right to use torture, which was over 100 pages long.
According to the Journal, the report was prepared after interrogators at the Guantanamo Bay detention facility expressed frustration over their inability to get information out of detainees there. Interrogators had begun using more aggressive techniques, like telling detainees that "I'm on the line with somebody in Yemen and he's in a room with your family and a grenade that's going to pop unless you talk," according to an official quoted by the Journal.
The report required Rumsfeld's approval for the use of four interrogation methods, and he has approved their use on two prisoners. It was not clear which methods were covered by that approval. At Guantanamo Bay, current practices included depriving detainees of food, making them stay up for four days, stress positions and body cavity searches.
The report concludes that "The infliction of pain or suffering per se, whether it is physical or mental, is insufficient to amount to torture," and says "Good faith may be a complete defense" to torture charges.
A separate report to be aired Monday by Australian Broadcasting Corp. reveals that the U.S. Army said in a letter to the Red Cross last year that Iraqis being held by American forces may not fall under international rules for the treatment of prisoners of war.
Maj. George O'Kane, an Australian army officer working in Baghdad for U.S. Judge Advocate Col. Marc Warren, helped draft the letter for the U.S. Army in response to Red Cross concerns that American guards at the Abu Ghraib prison had abused inmates.
It wasn't clear whether the Red Cross received the letter.
The letter was written in response to concerns about prisoners deemed to have "ongoing intelligence value," who had been found naked and in total darkness at the Baghdad prison.
The U.S. army took the view that "where absolute military security so requires, security internees will not obtain full Geneva Convention protection," the letter said.
The Abu Ghraib prisoners were treated "in the context of ongoing strategic interrogation," and under the circumstances "we consider their detention to be humane," said the letter, signed by Brig. Gen. Janis Karpinski, the former commander of prisons in Iraq.
Karpinski is the most senior officer suspended as a result of the prisoner abuse scandal at Abu Ghraib, and stands accused of failing to pay sufficient attention to what was happening at the prison.
In May, Stephen Cambone, the Pentagon's undersecretary for intelligence, told a U.S. Senate panel that troops in Iraq were under orders to abide by the Geneva Conventions, which dictate terms for humane treatment of wartime prisoners.
The Australian government had come under fire in recent weeks about what it knew about abuse of prisoners by American and British guards.
Australian troops captured up to 100 Iraqi soldiers during the war, but immediately handed them over to American or British forces.