I predict that when (not if, but when) the Federal Gov finally does make Marijuana fully legal, they will do whatever is required to make it retroactive. Even if it takes an amendment to the constitution specifically for this purpose it will need to be done, and will be considered minor paperwork. There will be no debate about whether it needs to be done. Who would argue against it? Perhaps only those Judges who handed down harsh sentences, because THEY are the individuals who morally deserve to be punished, and THEY are the ones who would go to jail if this were a just world.