(CNN)Sen. Bernie Sanders released a comprehensive plan late Thursday afternoon to legalize marijuana, begin a process to expunge old pot-related convictions and take steps to shape the emerging legal sales industry.

The proposal dropped, winkingly, at precisely 4:20 PM ET.

Sanders, a longtime proponent of marijuana legalization, would also ban tobacco companies from getting into the increasingly lucrative business, while creating a $20 billion grant program — using tax revenue from marijuana sales — to provide new capital to minority entrepreneurs.

Decades of harsh laws and sentencing requirements have “disproportionately targeted people of color and ruined the lives of millions of Americans,” Sanders said in a statement. “When we’re in the White House, we’re going to end the greed and corruption of the big corporations and make sure that Americans hit hardest by the war on drugs will be the first to benefit from legalization.”

Sanders unveiled the blueprint ahead of his appearance Saturday at the Second Step Presidential Justice Forum at Benedict College, an HBCU in South Carolina. The proposal takes a number of specific steps to address the disproportionately destructive impact federal drug policy has had on the African American community. The capital grant program will be would be administered through the Minority Business Development Agency.

As part of the plan, Sanders would create a federal clemency board to deal with past marijuana-related convictions, similar to a panel established in California. That body would instruct state and federal authorities to review all applicable cases to determine if a new or vacated sentence is required. It would also give prosecutors one year to appeal any decision, after which those convictions would be immediately vacated or expunged.

The 2020 Democratic candidates broadly agree on the need to reverse or roll back current drug laws. Decriminalizing possession and reducing sentencing guidelines, at the least, are popular among many of the leading primary contenders. But there is some disagreement over the scope of the reforms being suggested.

Sanders and Sen. Elizabeth Warren have said they would effectively legalize marijuana by executive action, with Sanders pledging to do it in his first 100 days in office. Their Senate colleague Cory Booker has been a leading reform advocate and his Marijuana Justice Bill counts Sanders, Warren, Sen. Kamala Harris and Sen. Michael Bennet among its co-sponsors.

South Bend, Indiana, Mayor Pete Buttigieg supports decriminalizing the possession of all drugs including marijuana, and said Wednesday during a visit to a marijuana dispensary in Nevada that past marijuana convictions should be expunged. Former Vice President Joe Biden does not back full legalization, saying he would leave that decision to the states. He would downgrade marijuana’s federal classification, to schedule II, which is the same as cocaine.

At Sanders’ rally this past weekend in Queens, the first after he returned to the campaign following a heart attack, he teased a plan to free prisoners convicted of certain drug-related crimes.

“We are going to end the horrifically destructive war on drugs and legalize marijuana,” Sanders said, tying the cause to a broader criminal and racial justice message. “And we are going to end the disgrace of 400,000 people right now locked behind bars because they are too poor to afford cash bail.”

In seeking to prevent major corporations from seizing on wider scale legalization, Sanders plans to incentive marijuana growers and distributors who choose to start non-profit or community co-op businesses that would benefit local economies. Existing companies that sell tobacco and cigarettes, along with those “that have created cancer-causing products or (are) guilty of deceptive marketing” would be locked out of the market, according to the Sanders plan.

At an event in Iowa in September, the Vermont independent promised that he was going to shift the bounty of marijuana sales from big corporations to the people who have been most heavily impacted by current, or only recently reversed, drug laws.

“I go to Nevada, and there are these big billboards, I don’t know if you’ve seen, and it says buy this or that brand of marijuana, have you seen this? They are advertising hemp,” Sanders said. “And I’m thinking that there are people in jail for doing exactly what these large corporations are doing, selling marijuana.”