Slipped this one in there...

A provision mysteriously tucked into the Military Commission Act (MCA) just before it passed through Congress and was signed by President Bush on October 17, 2006 , redefines torture, removing the harshest, most controversial techniques from the definition of war crimes, and exempts the perpetrators—both interrogators and their bosses—from prosecution for such offences dating back to November 1997.

Joanne Mariner of Human Rights Watch adds that the effect of this provision of the MCA is “that perpetrators of several categories of what were war crimes at the time they were committed, can no longer be punished under US law.”
As a whole, the MCA evolved out of the need to override the June 2006 Supreme Court declaration that the administration’s hastily assembled military commissions were unconstitutional. That momentous Supreme Court decision confirmed that all prisoners in US custody had to be held in accordance with the Geneva Convention’s Article 3, which prohibits “outrages upon personal dignity, in particular, humiliating and degrading treatment.” Through passage of the MCA, Congress and the President negated the corrective role of the courts in checking and balancing executive power.
A Senate aide involved in the drafting of the Senate version of the bill that was agreed upon by John McCain, Lindsey Graham, and John Warner, said, “We have no idea who [the extended impunity provision] came from or how it came to be.” White House spokesperson Dana Perrino said the stealth changes didn’t come from the counsel’s office, “It could have come from elsewhere in the White House or Justice Department,” she said, “but it didn’t come from us.”
Whatever the source, the amended provision was passed and is now a part of US law.