Unfortunately you have to give up your 2nd amendment right to purchase a firearm in order to get a prescription.. Form 4473 FBI background check: "Are you an unlawful user of, or addicted to, marijuana, or any depressant, stimulant, or narcotic drug, or or any other controlled substance?"
If you answer yes, instant denial. If you lie, you just committed a felony, goodbye 2nd amendment rights.
They need to make it legal at a federal level before I will try it.