After serving nearly three decades in federal prison for smuggling pot into Miami, Robert Platshorn would have been forgiven for spending the rest of his free days in quiet solitude. But the 69-year-old former leader of the Black Tuna Gang — which the DEA dubbed his '70s-era stoner collective of pot importers — has instead become one of the nation's most visible proponents of medical marijuana. Perhaps nobody in the world can better rue the irony that marijuana, which has never caused an overdose, is outlawed in most states, while lethal cigarettes and alcohol are freely peddled. Platshorn served more time, doing 29 years of a 64-year sentence, than anybody before or since for a marijuana offense. Since his 2008 release, his life mission has become touting the benefits of medical marijuana — including alleviating pain, quelling nausea, promoting sleep, easing the side effects of chemotherapy, and reducing inflammation — to a surprising but entirely logical demographic: elderly Floridians, whose physical ailments and limited budgets make them ideal joint-puffing self-medicators. Platshorn's "Silver Tour" puts on symposiums for seniors featuring experts and advocates of medical marijuana. Bobby Tuna, as Platshorn is nicknamed, has bought infomercial spots and billboards for the cause. (If you feel like donating to the shoestring campaign, check out his website.) He and others successfully pushed for an upcoming Miami Beach vote to decriminalize pot on the island. It's a shame that Platshorn lost nearly 30 years of his life for selling a natural and harmless plant. But if he succeeds, such an injustice won't happen again.