The International Convention Against Torture (ratified by the US in 1994) says
No exceptional circumstances whatsoever, whether a state of war or a threat of war, internal political instability or any other public emergency, may be invoked as a justification of torture.
I don't see how you could get more black and white with that statement. It (said convention against torture) also says
An order from a superior officer or a public authority may not be invoked as a justification of torture.
Not to mention a couple followup remarks:
Each State Party [and that does include the US -- sid] shall take effective legislative, administrative, judicial or other measures to prevent acts of torture in any territory under its jurisdiction.
Each State Party shall ensure that all acts of torture are offences under its criminal law. The same shall apply to an attempt to commit torture and to an act by any person which constitutes complicity or participation in torture.
And, hey, current US law? Also with the very black and white motif.
Sec. 2340A of the US Code. - Torture
(a) Offense. -
Whoever outside the United States commits or attempts to commit torture shall be fined under this title or imprisoned not more than 20 years, or both, and if death results to any person from conduct prohibited by this subsection, shall be punished by death or imprisoned for any term of years or for life.
(b) Jurisdiction. -
There is jurisdiction over the activity prohibited in subsection (a) if -
the alleged offender is a national of the United States; or
the alleged offender is present in the United States, irrespective of the nationality of the victim or alleged offender.
(c) Conspiracy. -
A person who conspires to commit an offense under this section shall be subject to the same penalties (other than the penalty of death) as the penalties prescribed for the offense, the commission of which was the object of the conspiracy.
And let's not forget the Geneva Conventions (I, II, III, IV).
Unfortunately, my government Just. Doesn't. Care.
In order to respect the president's inherent constitutional authority to manage a military campaign ... (the prohibition against torture) must be construed as inapplicable to interrogations undertaken pursuant to his commander-in chief authority.