After the events of 9/11 the Bush administration started torturing (by international standards of the word) people suspected of terrorism. For example "enhanced interrogation" was used which included things such as water boarding. It's my understanding this was allowed, because according to lawyers such as John Yoo, the methods that they were using did not fit the definition of what the US considered torture.
It has been found the John Yoo's argument was poor but he never faced charges.
Did anything illegal happen? Was it illegal for the government to use enhanced interrogator and was it illegal for John Yoo to advise the government it was legal to use such techniques(for example could he be guilty of criminal negligence)?