"it would be unfair to prosecute interrogators for actions they had been told were legal." thus fred hiatt. though it's not clear he endorses this as a principle, he lets it pass as obvious or trivial. but i propose to you that it is entirely and obviously absurd: exactly the sort of error that makes persons into the merest idiots and will extinguish our species. i realize that it's a tremendous burden, one which none of us, finally, can entirely bear: but no matter what you are told or by whom, you are responsible for what you actually do. and if you're letting john yoo do your moral deliberation for you, you deserve a lengthy prison sentence no matter what the result.
a moral system - such as all varieties of statism, or any political philosophy other than anarchism - which does not center responsibility in the individual, is fantastical and always the product of cowardice and a premonition of great evil.
of course, i guess it depends on who's telling you what's legal. if the voices in your head are telling you to kill, or some arbitrarily selected mental patient is telling you that torture is legal, that's an understandable reason to throw some chump into a box with scorpions. but if it's a justice-department lawyer, i say you're insane if you listen to him. a schizophrenic has no particular motive to encourage torture; a justice-department lawyer is adminstering a systematic justification for a massive spree of state sadism. if you decide to participate you are at fault, no matter what letterhead is on the memo.
probably even newspaper columnists/opinion editors could eventually be made to understand the inadequacy of 'alberto gonzales told me to' as a global moral excuse.