Not a lawyer, so this is just my understanding from reading about these issues, ok? There is no punishment from the legal system for HGH or Steroid use. There is for possession without a doctor's prescription. It may seem like a minor point because of it seems likely that if you use, you also possess, but the importance is in that a positive drug test isn't proof of a crime. Illegal distribution is another crime as well.

What the MLB owners and the Player's Union negotiate in their collective bargaining agreement is entirely different, and obviously the penalties are set out in that agreement, as well as a grievance procedure to resolve disputes on the matter.

PED is a term (including much more than steroids and HGH) used by sports authorities, not the government. The Feds, the State, or the local cops don't care why one is using a drug or what kind of boost they give to a person's athletic  "performance;" they just want to know if you possess them legally - as in, if a drug is a controlled substance under the law, do you have the right to have it?

I'm sure we have a few lawyers here that can point you to the laws themselves.