San Francisco will retroactively apply California's new marijuana legalization laws to prior convictions, expunging or reducing misdemeanor and felony convictions dating back to 1975, the district attorney's office announced Wednesday.

Nearly 5,000 felony marijuana convictions will be reviewed, recalled and resentenced, and more than 3,000 misdemeanors that were sentenced prior to Proposition 64's passage will be dismissed and sealed, Dist. Atty. George Gascón said. The move will clear people's records of crimes that can be barriers to employment and housing, reports the Los Angeles Times .

Proposition 64 legalizes, among other things, the possession and purchase of up to an ounce of marijuana and allows individuals to grow up to six plants for personal use. The measure also allows people convicted of marijuana possession crimes eliminated by Proposition 64 to petition the courts to have those convictions expunged from their records as long as the person does not pose a risk to public safety.

They also can petition to have some crimes reduced from a felony to a misdemeanor, including possession of more than an ounce of marijuana by a person who is 18 or older.