Uh, yeah, that's been said multiple times already. Nobody is talking about "legalizing" anything. We are talking about scheduling.
18 USC 922(g)(3) states:
"(g)It shall be unlawful for any person—
(3)who is an unlawful user of or addicted to any controlled substance (as defined in section 102 of the Controlled Substances Act (21 U.S.C. 802))
to ship or transport in interstate or foreign commerce, or possess in or affecting commerce, any firearm or ammunition; or to receive any firearm or ammunition which has been shipped or transported in interstate or foreign commerce."
ALL 5 schedules are controlled substances. That's the point.
Now, if you were convicted of a felony involving ANY controlled substance (say trafficking steroids), you might lose your right to possess a gun--as a felon (same if you were convicted as an embezzler, for example). THAT is different from getting an auto-DQ for using a controlled substance.