The US is a signatory to the UN Geneva Conventions. That is, not only have they been signed by the president, but they've also been ratified by the US Congress. And like the Constitution and legislation passed by congress and signed by the president, ratified treaties are the law of the land.
They are not optional. No matter how bad Bush and Rumsfeld wished it where otherwise:
Top Pentagon officials conceded on Thursday some of the interrogation methods approved for use by the U.S. military on Iraqi prisoners may violate the Geneva Convention governing treatment of war prisoners [...]
During a Senate Armed Services Committee hearing, Democrats confronted Deputy Defense Secretary Paul Wolfowitz, the No. 2 official at the Pentagon, and Gen. Peter Pace, the No. 2 U.S. general, with "rules of engagement" for interrogations approved by the top commander in Iraq, Lt. Gen. Ricardo Sanchez.
These methods included sleep and sensory deprivation, forcing prisoners to assume "stressful" body positions for up to 45 minutes, threatening them with guard dogs, keeping them isolated for longer than 30 days, and dietary manipulation.
Sen. Jack Reed asked Pace if a foreign nation held a U.S. Marine in a cell, naked with a bag over his head, squatting with his arms uplifted for 45 minutes, would that be a good interrogation technique or a Geneva Convention violation.
"I would describe is as a violation, sir," replied Pace, vice chairman of the Joint Chiefs of Staff [...]
Reed later asked Wolfowitz a similar question. Wolfowitz initially tried to sidestep it, but eventually replied, "What you've described to me sounds, to me, like a violation of the Geneva Convention."
By violating the Geneva Conventions, the people who helped enable it are literally criminals.