San Francisco will expunge and dismiss thousands of misdemeanor and felony marijuana convictions for those sentenced prior to legalization of marijuana in California — even if those with prior convictions don't file a petition, District Attorney George Gascón said Wednesday.

The move could provide a model for other U.S. city and state governments to follow as the push to legalize marijuana continues to gather steam.

The District Attorney's office announced its intent to retroactively apply new, more lenient rules on marijuana possession and legalization to drug cases dating back to 1975.

"While drug policy on the federal level is going backwards, San Francisco is once again taking the lead to undo the damage that this country's disastrous, failed drug war has had on our nation and on communities of color in particular," Gascón said in a statement.

Beyond legalizing marijuana for adult use, the recently implemented California measure, known as Proposition 64, enables those with past convictions to petition a court to recall or dismiss their cases. But in San Francisco, only 232 petitions have been filed as of Sep. 2017. Statewide, 4,885 petitions were filed in that time, according to the Drug Policy Alliance, one of the organizations that helped write Proposition 64.

"The pathway to expunging records is one of the most important passages of Proposition 64, but there hasn't been as much coverage, so people aren't aware they can benefit from it," said Laura Thomas, Drug Policy Alliance interim director for California.

The process requires filing paperwork, paying a fee or even retaining an attorney, which Thomas emphasized can preclude vulnerable populations, like minorities, from participating. And it's these populations that are disproportionately impacted by felony and misdemeanor drug convictions.

When marijuana arrests skyrocketed in 2000, the percentage of black people arrested rose from 34 to 41 percent of the total, according to the city's Cannabis Equity Report. African Americans represented only about 8 percent of the city's population at the time.

As Gascón has long claimed reducing criminal conviction disparities along race lines as a cornerstone of his tenure as DA, he made moves to dismiss convictions en masse.

"Prop. 64 sets a new benchmark of how to legalize marijuana within a reparative justice frame," Thomas said. "What Gascón did is move that to the next level to ensure everyone can get access to the release Prop. 64 promised."

Gascón's office intends to review, recall and re-sentence as many as 4,940 felony convictions and dismiss and seal 3,038 misdemeanors.

"This example, one of many across our state, underscores the true promise of Proposition 64 – providing new hope and opportunities to Californians, primarily people of color, whose lives were long ago derailed by a costly, broken and racially discriminatory system of marijuana criminalization," California Lieutenant Governor Gavin Newsom said in a statement.

"This isn't just an urgent issue of social justice here in California – it's a model for the rest of the nation," he added.

Gascón's unprecedented action comes at a turbulent time for the U.S. marijuana industry. Days after the nation's largest marijuana market opened for business Jan. 1, Attorney General Jeff Sessions moved to undermine previous federal guidance for state-by-state marijuana regulation, threatening burgeoning industries in several states.

Gascón is just the latest leader from a cannabis-friendly state to come out in defiant opposition to Sessions' actions.