anglolawyer
Banned
IANAL but I think what Anglolawyer is saying that the only possible defense would to argue on a basis of necessity. I.e that a case could potentially be made (solidity of said case to be evaluated) that they acted from their view of the situation believing that it was necessary to do what they did. IANAL so can't evaluate how common law and statute could be directed in this case to work but I am sure we have all seen cases where flimsy defences have won the day.
There appear to be no English cases in which necessity has been raised as a defence to an allegation of assault involving torture. It's certainly the only defence I can think of and it would take very particular circumstances for it to have a chance. The one where the cops only have 20 minutes to find the baby in the car and the thief won't tell them where it is ought to have a fair prospect of success I think. There are all kinds of other ways the law can reflect our general feeling in that case that no wrong has been done - there is no obligation to prosecute for example (the case might fail a public interest test) and the court can order an absolute discharge even in case of a conviction.
All of which is very well, but it doesn't get the CIA off the hook.