Los Angeles County district attorney George Gascón said on Monday that his office would expunge the convictions of tens of thousands of people found guilty of cannabis-related offences before California legalised the drug in 2018.
It brings the total number of convictions dismissed in LA County to around 125,000, following another 66,000 which were expunged last year.
Mr Gascón said: “Dismissing these convictions means the possibility of a better future to thousands of disenfranchised people who are receiving this long-needed relief.
“It clears the path for them to find jobs, housing and other services that previously were denied to them because of unjust cannabis laws.”
His decision was backed by the LA County public defender’s office and by its “alternate public defender” Erika Anzoategui, who represents citizens in cases where the public defender has a conflict of interest.
“This sends the right signal to the community that the nation was wrong in its ‘war on marijuana’ and that criminal convictions for marijuana offences have a disproportionately negative impact on communities of colour,” Ms Anzoategui said.
LA County governs the broader Los Angeles metropolitan area, which is far larger than the city of LA itself and covers an estimated 10 million people.
Californians voted strongly to legalise recreational cannabis in a statewide referendum in 2016, backing a ballot measure called Proposition 64 by 57 per cent to 43.
The drug remains illegal at a federal level, which limits the nascent weed industry’s ability to raise capital and conduct business across state lines.
As well as allowing regulated weed sales starting in 2018, Proposition 64 kicked off a rolling process of petitions and reviews designed to erase the stain of prior convictions for people whose conduct would not have been illegal under the new law.
Mr Gascón’s decision went beyond that programme, working with a non-profit group called the Social Impact Center to identify eligible convictions stretching back to 1975.
His office said that some of the beneficiaries might be surprised because they believed their conviction was dismissed last year or did not know they were eligible.
First declared by President Richard Nixon in 1971, the war on drugs has dominated US policing for decades without significantly reducing the rate of fatal overdoses or the availability of illicit substances.
Critics say the drug war drove ballooning rates of imprisonment across the US and wreaked havoc on generations of black Americans whose communities were targeted by police.