Fact is, he's addicted. Essentially a junkie. I know that's harsh given the fact that the substance in question is pot. But, there it is. He's demonstrated that he can't quit using despite the tremendous rewards of staying away from it and the horrible dangers of using it. That means he's incapable of policing his behavior. IE, a junkie.
Sorry Martavis. People with addictive personalities get hooked on all kinds of things. He likely has issues with other substances as well. Without serious counseling and a true core belief that he needs to change his behavior he has no real hope of doing so. And given the fact that he has a lavish lifestyle and adoring fans, I seriously doubt there is any real impetus for him to change his behavior.
In other words, cut the cord. Use the time to find a replacement because in the end he'll be unreliable at best. Hate me if you like, hell, use my purely reasonable and logical arguments as bulletin board material but the fact is, the kid's a junkie. Just like Ricky Williams. Talented, sure but ultimately he only cares about getting stoned and taking care of himself. It's sad, but there it is.