Christopher Dean Smith was arrested on a marijuana farm in northern California in 2014.

Smith, now 28, said he was with a friend on the property in the town of Chico, about 145km north of Sacramento, when two vehicles pulled up. Federal law enforcement agents approached the pair and told them to get on the ground.

Smith was arrested and accused of cultivation of marijuana plants and possession with intent to sell a controlled substance.

He told Al Jazeera he was not working on the farm at the time, but after fighting the charges in court for a year, he accepted a deal and pleaded no contest to cultivation.

"Since then, I've had to change my life around," he said.

He was sentenced to three years of probation, which came with a series of restrictions. It also put a felony on his criminal record.

"Since I've had the charges on my record, it's completely changed everything that I've had going for me. I lost my place. I lost my job," Smith said.

"Honestly, I didn't know how much of a negative impact it would have on the rest of my life."

Resentencing past offences

The state of California legalised recreational marijuana use in November 2016, and it will become legal state-wide on Monday. That means anyone 21 and older will be able to buy marijuana from a licensed store, known as a dispensary.

The legislation also allows people who, like Smith, were previously convicted of a marijuana-related offence to apply for resentencing.

Smith said he has filed to have his case reheard by a judge, who may then rule to have his conviction reduced from a felony to a misdemeanour on his criminal record.

The resentencing provisions of Proposition 64, California's marijuana legalisation initiative, have been in effect since last year, said Eunisses Hernandez, a policy coordinator at the Drug Policy Alliance, a group working to end drug prohibition. But few people know about the resentencing provision, which applies to people who are currently imprisoned or out on parole, Hernandez told Al Jazeera.

Individuals who apply for resentencing may be released from prison or have the charge on their criminal record reduced. Felonies may be lowered to misdemeanours, misdemeanours to infractions, or infractions to an outright dismissal of charges.

Resentencing will likely affect thousands of lives, since at least 500,000 marijuana-related arrests have been recorded in California over the last decade, Hernandez said.

"By [Proposition] 64 passing, we not only are able to repair some of the damages that have already occurred ... but we're also preventing a lot more people from getting put into the criminal justice system because of these laws," she said.

Between 2001 and 2010, more than eight million marijuana-related arrests were recorded in the United States, 88 percent of which were for possession, according to a report by the American Civil Liberties Union (ACLU) released in 2013.

Individuals with a recorded criminal conviction face thousands of barriers across all areas of life.

"If you got convicted of a simple possession of marijuana [charge] ... that could prevent you from getting jobs, getting housing, getting supportive services," Hernandez said.

Marijuana arrests also disproportionately affect people of colour.

Black people are 3.73 times more likely to be arrested for possession of marijuana than white people, even though both groups consume the drug at similar rates, according to a report by the ACLU.

Pros and cons

California is one of fewer than a dozen US jurisdictions that have passed motions to legalise recreational marijuana use in the past decade. The others include Colorado, Oregon, Alaska, Maine, Washington state, Washington, DC, Nevada and Massachusetts.

More states have already legalised medical marijuana, requiring people to have permission from a doctor to buy the drug. By contrast, when recreational use is legalised, customers do not need a special permit.

The US state of Oregon, which legalised recreational marijuana use in 2015, also passed legislation that allows people to apply to have their possession convictions erased from a computerised criminal history database, under certain conditions.

Several groups in the US have urged authorities to include changes to drug-related criminal offences in their efforts to legalise recreational marijuana.

Eric Sterling, executive director of The Criminal Justice Policy Foundation, a non-profit group specialising in drug policy issues, said criminal sentencing reform was "not part of the conversation" in early efforts to legalise recreational marijuana in the US.

Proponents of marijuana legalisation feared that allowing people with past drug convictions to get out of jail or reduce their sentences would lower the chance that the laws would pass at all. "There was, in many cases, a reluctance to bring this up," he told Al Jazeera.

Today, opponents of resentencing provisions often argue that retrying these cases puts "a very, very large potential burden on the courts", Sterling said.

Law enforcement officers may also contend that a guilty plea to marijuana possession may follow the dropping of more serious charges, such as possession with the intent to distribute - "and so to make a blanket change without looking at all of the underlying facts of the arrest would mean that more serious offenders would have their records expunged", Sterling said.

'Second chance'

Ultimately, Sterling said it is most important to make sure people who may be affected by a resentencing law are aware that the law exists in the first place.

"The key thing, I think, is the ability for people to re-enter the economy and society free of those encumbrances," he said. "We would also say they are eligible to vote, they are eligible for jury duty, that all of their civil rights are restored."

Meanwhile, Christopher Dean Smith, who now works as a chef in California, said getting his felony drug conviction expunged or reduced would allow him to go back to what he loves.

"I can go back into the industry for recreational marijuana, which is one of my passions ... helping people," he said.

And for Smith, that would ultimately be "a second chance".