Maybe when the person was young they did something and they are older and have proven to not be a repeat offender? Rare case, I know, but still possible.

To me it just sounds like a legal out to say any or all of them are deemed ethically unacceptable so they can fire them without legal issues. Japan has whack employment laws, and businesses will almost always try to make you quit before they fire you. I can see this wording being related to something like that.