San Francisco Wipes Out Weed Convictions From 1975 The city will retroactively apply California’s new marijuana laws to prior convictions. Misdemeanors and felonies from 1975 will either be reduced or expunged. This means nearly 5,000 marijuana convictions will be reviewed and about 3,000 misdemeanors will be dismissed. The new measure is part of California’s Proposition 64 which legalizes possession and purchase of one ounce of marijuana.