My opinion: Anyone who took part in it either knowing it is illegal or even if the person should have known it is illegal considering his/her position.
Same goes for persons that didn't necessarily know about it but acted negligent or ignored standard procedures that are in place to prevent such a thing.
> But in general a CEO should have a duty to ask questions why a certain division seems to be doing well
Could be negligence, I don't know the specifics here. If it was then he has to be held accountable. But his head might roll in the end regardlessly as people always need a scapegoat, no matter if it's his fault or not. Yet when the government takes action it should not do so just to punish a scapegoat, they should punish because the person broke a law. (if the shareholders fire him even though it's not his fault I couldn't care less, it's their investment and they do not have to act rationally if they want to)
As a general rule, we don't hold people criminally liable for simple negligence.
But in general a CEO should have a duty to ask questions why a certain division seems to be doing well. Maybe it has to do with earnings targets that are simply unachievable? I see that in my own company. The top guys are setting shorter and shorter deadlines and in my view the quality of engineering suffers. Top management doesn't technically know when people are cutting corners but they could easily have listened to people that the demands are too high.