On June 8, 2004, the Washington Post published an article that described a memo drafted by the Justice Department that attempted to define the boundary of the law as it applies to torture.  Later, the Washington Post announced that it would release that memo.

 PDF of the Aug. 1, 2002 White House Memorandum

 This memo described what government interrogators could and could not do.  Essentially, the memo suggested that legal interrogation techniques included anything that did not include death, including psychologically damaging techniques.  The memo states that the opinion of the Justice Dept. is that torture "must be equivalent in intensity to the pain accompanying serious physical injury, such as organ failure, impairment of bodily function, or even death."  This memo supported the legal basis for the torture committed at Abu Ghraib and Guantanamo Bay.

 The US anti-torture statute

A 1963 CIA Torture Manual declassified in the late 90's.  This is interesting reading; my favorite part is where it says that interrogators must contact headquarters for approval before illegally interrogating someone.

The ACLU recently published formerly-secret Bush administration Office of Legal Counsel Torture Memos.

 August 1, 2002 Jay Bybee (OLC)  to John Rizzo (CIA)

This 18 page memo instructs the CIA that facial slaps, walling (see memo), waterboarding, and placing the inmate in a small box with an insect do not constitute torture.

May 10, 2005 46-page memo from DoJ to John Rizzo (CIA)

This lengthy memo goes through all the "enhanced interrogation methods", such as the ones described in the above memo and others, and suggests that they do not violate the federal anti-torture statute.

May 10, 2005 206-page memo from DoJ to John Rizzo (CIA)

While the above memo considers the legal issues involved with the techniques individually, this memo considers them in combination.  Our cause fares no better off.

May 30, 2005 40-page memo from DoJ to John Rizzo (CIA)

This memo seeks to legally justify the above techniques under the UN Convention Against Torture

 Other important Memos (thanks Scott)

All of the following, and others, can be found at this page.

Memorandum Regarding Status of Certain OLC Opinions Issued in the Aftermath of the Terrorist Attacks of September 11, 2001 (01-15-2009)

This one discusses the memos concerning the liberty of individuals abroad, amongst other things, and the current legal counsel's concern that the old opinions are not authoritative.

Memorandum Regarding Constitutionality of Amending Foreign Intelligence Surveillance Act to Change the "Purpose" Standard for Searches (09-25-2001)

This memo from John Yoo on September 21, 2001, although not concerning torture, is important.  It suggests that the president may legally authorize warrantless searches.

This memo, again from John Yoo but in October of 2001, suggests that the military may legally operate inside the United States against terrorist organizations.  Specifically, it says that a military commander may conduct a raid on a terrorist cell in the US without probable cause or warrant.  Basically, it allows the military to invade our homes for any reason (or no reason).  This is the most grotesque legal manipulation that the Bish administration attempted.  Fortunately, this memo from October 2008 calls into question the opinions in the 10/2001 memo.

Memorandum Regarding the President's Power as Commander in Chief to Transfer Captured Terrorists to the Control and Custody of Foreign Nations (03-13-2002)

This memo suggest that thepresident has the power to transfer captured terrorists into the custody of foreign governments for interrogation.  These foreign government, of course, may not have the same anti-torture laws that the US has.  This is one way that many suspected terrorists found themselves tortured during interrogations.  Also, there are many concerns that can be noted here of who, exactly, counts as being a terrorist.

Memorandum Regarding Swift Justice Authorization Act (04-08-2002)

This memo suggests that the trials for suspected terrorists are actually battlefield operations and thus fully fall under the authority of the commander-in-chief.  As a result, if my understanding of the memo is correct, congress has no say in the matter of how detainees are treated.

Memorandum Regarding Determination of Enemy Belligerency and Military Detention (06-08-2002)

 This memo attempted to legally justify military arrest, detention, and trial of US citizens on US soil.

Memorandum Regarding Applicability of 18 U.S.C. § 4001(a) to Military Detention of United States Citizens (06-27-2002)

This memo basically says that since the president is the Commander-in-Chief, he can do anything.  He can even ignore the US law that says "No citizen may be imprisoned or otherwise detained by the United States except pursuant to an act of Congress."  Since he is CinC, the Bush Smitherses that wrote this say he can ignore it.  They even cite the Constitution for the authority.  This is as bad as it gets.