Of the two of you, which is the boss of him?

I know exactly how you feel. My best friend dropped out of school one semester away from graduating. I wish I could tell you that we had a nice talk and I motivated her enough to get her life back together, but that wasn't what happened. Instead, we went out drinking, I felt brave enough to tell her that I felt she was wasting her potential, and now we don't talk. Go figure. In my case, I maybe should have kept my big mouth shut, but every situation is different. Maybe your friend could handle a wake-up call.