how so?
As I said in a previous post, most (if not all) states & municipalities have a separate crime for "drug abuse" or "drug use".
If Rush was abusing these drugs then he broke the applicable law(s).
My understanding is that not many people are charged with just that crime. Rather, they are tacked on by prosecutors to other related crimes such as possession, etc. so that, soon, a person in such trouble has multiple charges against them.
I still don't see the source for your assertions? I'd like for you to cite for me any case law that list abuse of prescription drugs is a criminal offense.