He didn't do anything illegal. He may have done something unethical. The two are not the same.
Researching the law and writing a memo about what you find is not an illegal act.
All too often I see the discussion around Yoo hinge on conflating the two -- illegal and unethical -- and it doesn't do anything to further the discussion.
+1. I tend to agree with you here. Just because he argued that a particular action was legal and protected by the law of the land doesn't mean he is guilty of a crime. Sure, President Bush might have used Yoo as political and legal cover to do what he wanted, but it was the President and not Yoo that did it.
Of course, there may be some nebulous crime of association here of which I am not aware. But still.
I mean, obviously there's a lot I don't know about the situation, and that the public doesn't know. Yoo could very well be guilty of one or several crimes. But we don't know, and as it stands with what we do know -- he wrote a goddamned memo, with abhorrent content, but abhorrent /= illegal -- isn't enough to convict him of anything.
But two people are responsible for that at any one time: first, it was Bush and his AG, for not investigating; now, the onus is on Obama and Holder to begin an investigation to figure out what happened and how.
Until then the culpability, I think, lies with them.