My son needs to be in rehab what can I do?

[Lisa]

My son is 18 years old. I found out he was doing coke and asked him about it and he admitted it. That was a month ago. He supposedly quit. But I still see him in mood swings and last night we got in a pretty ugly argument because he won't get out there and look for a job but always wants money for gas or cigs. So I am guessing he is still doing it. I don't really know. Maybe he needs to go to rehab. I do know he is smoking weed. My problem is since he is 18 he is of legal age. Is there anything I can do to make him go to rehab? I've heard I can go to court and get custody of him. I am going to find out about that. If so I am definitely doing that. I can't bear to see him this way. He was such a great kid! But now I just don't know anymore. I've never dealt with this kind of stuff before.