I have a friend who is currently going through hell with her 21-year-old son... there is NOTHING she can do from a legal standpoint, the cops have been no help, she has literally NO legal recourse or power to do ANYTHING. That's just how it is, it doesn't matter how much she would love to help, doesn't matter she wants to help.. Once you have reached adulthood, your parents don't have any legal control whatsoever. In fact, he recently tore her house all to hell, and she called the police... when they arrived, they asked her if he lived there? She told them he did, and they told her, there was nothing they could do, it was his house too.
So, as much as you might think it's a cop out, and there are things that can be done, actually DOING things, is much more difficult. Perhaps this shouldn't be the case, but currently, it is the case.