Not to be a downer but I just wanted to say that if the parents are "forcing" their son to go to treatment the chances of it working aren't very good. From what I understand treatment has a very low success rate even if the patient wants to be there. If someone else is forcing them well...chances aren't very good.
I know that when I was younger I got into some trouble for pot and my parents tried all manner of "forcing" me to quit. Sent me to rehab, drug tested me, the whole gambit. The thing is at that age the natural instinct is to push back against your parents so it only made me more determined to smoke. Sure, they could force me to stop for a little while but eventually I would find a way around it, cheat drug tests, etc.
It wasn't until I got older and unfortunately got into some heavier and more destructive drugs that I realized I had a problem and made the decision to quit on my own. When I was younger there was nothing my parents could have done that would have made me stop. I'm sure it sucks to see your kid headed down the wrong path and not be able to stop him but unfortunately there are some things people have to find out for themselves.
I'm not saying that parents shouldn't try to help their children and that parents don't have the right to set boundaries for their children. I'm just saying that treatment is not a magical cure. May I ask what kind of addiction / other issues are going on? Teenage rebellion is one thing, serious chemical dependency is another.