San Francisco District Attorney George Gascón has announced that he will retroactively apply California’s new marijuana legalization law to past criminal charges.

The move will lead to the expungement (removal from criminal records) of more than 3,000 misdemeanor marijuana convictions dating back to 1975. This will be one of the largest batch of expungements in the city’s history.

“Instead of waiting for people to petition — for the community to come out — we have decided that we will do so ourselves,” says Gascón. “We believe it is the right thing to do. We believe it is the just thing to do.”

According to Gascón, prosecutors will also review and potentially expunge 4,940 felony marijuana cases.

The move is made possible thanks to the passage of Proposition 64 in 2016. The initiative legalized the possession, use and licensed distribution of up to an ounce of marijuana for those 21 and older.