The chronology works against him:
It increasingly appears that the Bush interrogation program was already being used before Yoo was asked to write an opinion. He may therefore have provided after-the-fact legal cover. That would help explain why Yoo strained to take so many implausible positions in the memos.
It also appears that government lawyers had told Bush administration officials that some of the techniques already in use were illegal, even criminal. In fact, a senior Pentagon lawyer described to me exchanges he had with Yoo in which he stressed that those using the techniques could face prosecution. Yoo notes in his Pentagon memo that he communicated with the Criminal Division of the Justice Department and got assurances that prosecutions would not be brought. The question becomes, was Yoo giving his best effort at legal analysis, or was he attempting to protect the authors of the program from criminal investigation and prosecution?
In any case, Yoo kept the program running.