You can often tell if someone understands how wrong their actions are by the lengths to which they go to rationalize them. It took 81 pages of twisted legal reasoning to justify President George W. Bush's decision to ignore federal law and international treaties and authorize the abuse and torture of prisoners.

Eighty-one spine-crawling pages in a memo that might have been unearthed from the dusty archives of some authoritarian regime and has no place in the annals of the United States. It is must reading for anyone who still doubts whether the abuse of prisoners were rogue acts rather than calculated policy.

The March 14, 2003, memo was written by John C. Yoo, then a lawyer for the Justice Department. He earlier helped draft a memo that redefined torture to justify repugnant, clearly illegal acts against Al Qaeda and Taliban prisoners.

The purpose of the March 14 memo was equally insidious: to make sure that the policy makers who authorized those acts, or the subordinates who carried out the orders, were not convicted of any crime. The list of laws that Yoo's memo sought to circumvent is long: federal laws against assault, maiming, interstate stalking, war crimes and torture; international laws against torture and cruel, inhuman or degrading treatment; and the Geneva Conventions.

Yoo, who inexplicably teaches law at the University of California, Berkeley, never directly argues that it is legal to chain prisoners to the ceiling for days, sexually abuse them or subject them to waterboarding - all things done by American jailers.

His primary argument, in which he reaches back to 19th-century legal opinions justifying the execution of Indians who rejected the reservation, is that the laws didn't apply to Bush because he is commander in chief. He cited an earlier opinion from Bush administration lawyers that Al Qaeda and Taliban prisoners were not covered by the Geneva Conventions - a decision that put every captured American soldier at grave risk.

Then, should someone reject his legal reasoning and decide to file charges, Yoo offered a blueprint for escaping accountability.

American and international laws against torture prohibit making a prisoner fear "imminent death." For most people, waterboarding - making a prisoner feel as if he is about to drown - would fit. But Yoo argues that the statutes apply only if the interrogators actually intended to kill the prisoner. Since waterboarding simulates drowning, there is no "threat of imminent death."

After the memo's general contents were first reported, the Pentagon said in 2004 that it was "no longer operative." Reading the full text, released this week, makes it startlingly clear how deeply the Bush administration corrupted the law to give cover to existing and plainly illegal policies.

The memo is also a reminder of how many secrets about this administration's cynical and abusive policies still need to be revealed. As Senator Edward Kennedy noted, the release of the Yoo memo is a reminder that neither Congress nor the American people have seen the policy memos that govern interrogations today. We know of at least two being kept secret for supposed reasons of national security, including one authorizing waterboarding.

When the abuses at Abu Ghraib became public, we were told these were the depraved actions of a few soldiers. The Yoo memo makes it chillingly apparent that senior officials authorized unspeakable acts and went to great lengths to shield themselves from prosecution.