As for Rush being prosecuted, it's very easy. People who become addicted to painkilling drugs are never charged with any crime relating to acquiring the drugs from doctors.
When I was a young man I developed a pain problem for which no etiology could be determined. I went to see all kinds of specialists (even head-shrinkers), each of whom had his or her own idea of what was causing it but none could cure it.
The pain was severe enough to require mild narcotics (Tylenol#3 and Tylenol#4) and was highly distracting.
Then I came across a neurologist who told me, "You know, I think I know what is causing this. It is a very, very rare neural disorder that causes a pain path to be set up and that path had to be "jumbled" (my term)." He told me that this possibly could be cured by a drug he used often in his practice. He gave me the medication (a non-narcotic used by people who have epilepsy), which in a period of six weeks or so, erased the pain. That was in 1982 and I have been pain-free ever since.
If this had happened in Florida (it didn't), I suppose I would be in jail.