My Nephew Appears To Be Addicted To Pot. He's Been

My nephew appears to be addicted to pot. He's been smoking it extensively for some time, several years, and has now graduated to stealing from relatives to either pay his marijuana debts or buy more. He stays broke, cannot keep a job, and no close relative will allow him to move in because he is a confirmed thief. His mother and father have been attending counseling with him, which for a minute seemed to be helping. He will not consent to entering a program that might help him. We are convinced from his behavior that he has bipolar disorder or some mental illness. Currently, he is sleeping in his car, that is uninsured, or spending as many nights with friends as they will allow. At some point, he is going to be arrested because of not having insurance or plain disrespect for police. We don't know what to do. Is there anything we can do before he is arrested or loses his life?