"Getting out early" is not something done at the federal level. The President could pardon him. That's about it. Let's pretend that Congress legalizes marijuan

"Getting out early" is not something done at the federal level. The President could pardon him. That's about it. Let's pretend that Congress legalizes marijuana. The folks still in prison who had been convicted of selling or transporting it would not get released - unless the statute removing it from Schedule 1 also specifically required releasing those already convicted.