I did some reading abt this topic. The Military Commissions Act bars, under all circumstances, treatment of prisoners that inflicts serious physical or mental pain or suffering.
Two of the chief sponsors of the legislation, senators John McCain and John Warner - both senior Republicans - say it outlaws waterboarding. The US army also revised its field manual to specifically ban waterboarding and other techniques as "cruel, inhuman and degrading treatment" that is banned by the Geneva accords.
As early as 1901, a US court martial sentenced Major Edwin Glenn to 10 years hard labour for subjecting a suspected insurgent in the Philippines to the "water cure".
After the second world war, US military commissions successfully prosecuted as war criminals several Japanese soldiers who subjected US prisoners to waterboarding. In 1968, a US army officer was court martialled for helping to waterboard a prisoner in Vietnam.
So? Contradiction?