My understanding is that he failed the drug test at a title fight, so that was why he had the belt removed. He was then suspended from the UFC until he gets his shit together.
The failed drug test bit is in the past (also tested for something that it shouldn't have) and also resulted in no criminal proceedings therefore not violating the Code of Conduct. The problem here is that he committed a felony when he fled the scene of an accident where the other driver was injured. This is the issue. The shitheel aspect of it comes into play when he returns to the scene, gathers a wad of cash from the vehicle and then merrily fucks off again. Oh, add to this wonderful glimpse into the mind of a possible sociopath that he doesn't report to the police for a day or so, presumably (by some in the media who love speculation) to get out of his system whatever was in it that contributed to the crash. "Respectfully". TL;DR It isn't about the drugs or the assholeishness. That isn't part of the Fighter Code of Conduct.