Virgil Grant is riding the high on California's cannabis legalization, with a burgeoning empire that already comprises three dispensaries, two plantations and a line of apparel.

His success has come as some compensation for the six years lost inside the federal prison system for dealing a drug which was outlawed for non-medical use before January 1.

In his discreet boutique in South Los Angeles, he proudly shows off his latest wares -- a reusable tea flask infused with CBD, a non-psychoactive element of cannabis -- and ointments sold in pretty jars.

Grant found himself on the wrong side of the United States's decades-long "war on drugs" before the start of the massive groundswell for cannabis legalization, locked up after being arrested by federal agents in 2008.

"You have a lot of people of color that were arrested and sent to prison and jail, (such) as myself, for marijuana crimes, non-violent drug offenses," he told AFP.

"We're moving forward and we're talking about legalization... there are still people sitting in prison for marijuana crimes, but we're out here selling marijuana legally. You know, that doesn't make sense."

Cannabis has been legalized in about 30 US states in one form or another, although it remains outlawed at the federal level.

Although recent figures are difficult to ascertain, there were more than 11,000 people in federal prisons for cannabis offences in 2012, according to a study by the Urban Institute think tank.

- 'You lose everything' -

"These people should be freed immediately and their records should be expunged. This is not happening fast enough," said Grant, co-founder of the California Minority Alliance (CMA), which advocates for minority rights within the weed-growing industry.

According to the American Civil Liberties Union, 8.2 million people were arrested for dealing or using cannabis between 2001 and 2010 -- four black people for every one white, despite similar consumption levels and dealing activity.

Cat Packer, head of LA's department of cannabis regulation, says disproportionate arrests of non-whites have occurred only because police were "more active in those communities."

But the impact on African-Americans and Hispanics has been devastating, plunging entire families into penury.

"You lose everything. They take your cars, your money," recalls Grant, who laments missing out on his five daughters growing up.

"Then there's the mental damage you do to these young kids when their father is taken from the home. From leaving a comfortable lifestyle, to have to look for some kind of assistance."

Cannabis offenders often find life on the outside as challenging as incarceration, their drugs convictions a black mark that stops them getting jobs, housing and some benefits, condemning them to remain in crisis.

In areas where cannabis consumption has become legal, authorities say they are gaining awareness of the socio-economic damage of previous regressive policies and, as a result, putting remedial measures in place.

- 'Not the right color' -

Los Angeles, Oakland and Portland, for example, are aiming to give priority when handing out cannabis trading licenses to those who have suffered from the "war on drugs."

Meanwhile the CMA is campaigning throughout the country for disadvantaged minorities to get better access to the embryonic legal cannabis sector.

"It shouldn't take a million dollars to get a license... If we don't put in some provisions it will be a white, male-run industry," Grant argues.

Cities like San Diego, San Francisco and Seattle want to offer amnesty for thousands of low-level cannabis convictions, while many Californian associations are also organizing "clinics" to help ex-convicts, most of them men from minority backgrounds, get their criminal records expunged.

Eddie Erby, an employee in one of Grant's dispensaries, was arrested at age 18 for selling marijuana and spent 10 years behind bars. Now, at 52, he has turned his life around.

"It was a way of fast money because you couldn't get a job because you're not the right color," he says as he weighs out marijuana for a customer.

Grant regularly hires ex-convicts like Erby and has only basic requirements for prospective employees.

"Be on time, don't steal, and you can have a job," he says.

And there are plenty of cannabis jobs going in a market already estimated to be worth nearly $20 billion in the United States, a figure that is expected to double within three years.