RICHMOND — Virginia Gov. Ralph Northam said Monday that he supports the legalization of marijuana, following the release of a study that found Virginia could generate $300 million in taxes from the sale of the substance.

Northam (D) plans to work with the General Assembly on legislation during the regular session that convenes in January, although the process could take two years to play out.

The legislature passed a bill this year that decriminalized possession of marijuana, creating a $25 civil penalty for a first offense. That measure, which passed with bipartisan support and which Northam signed into law, also mandated a study on the issue of legalization by members of Northam’s Cabinet and staff. That group plans to issue its report at the end of the month but supports legalization.

The governor had campaigned on the issue of decriminalization when he ran in 2017 but had not previously expressed support for full legalization. He called a news conference Monday to discuss the topic.

“We are going to move forward with the legalization of marijuana in Virginia,” Northam said. “I support this, and I’m committed to doing it the right way.” He added that “the time is right” and pointed out that Virginia would be the first state in the South to legalize marijuana.

Northam said that he has never personally tried marijuana but that he has come to support legalization after learning about how communities of color are disproportionately affected by its criminalization.

He said studies have shown that minority and White populations use marijuana in similar rates but that people of color are three times as likely to be arrested for it. He also said he has seen the benefits of marijuana-derived substances in treating children with epilepsy and other disorders in his practice as a pediatric neurologist. And he said he has followed public opinion polls that show increasing support for legalization.

Two-thirds of Americans think marijuana should be legal, according to Pew Research Center data.

Several Republicans in the General Assembly supported decriminalizing marijuana but have expressed reluctance on pursuing full legalization. On Monday, leaders in the Senate declined to weigh in until they had seen more details.

“A lot of other states are already doing it, but we’ll see,” said Del. Terry G. Kilgore (R-Scott), who did not support the decriminalization bill in the last session. “I’ve always thought of it as a gateway-type drug, but I guess that’s what the session will be for this year.” He added that he was unlikely to favor this step, “but I’ll listen to all the arguments. . . . It had some support on our side.”

Sen. Adam P. Ebbin (D-Alexandria), who sponsored a decriminalization bill this year, said he was already working on a legalization measure for next year and was thrilled by Northam’s support.

“This is a major and important positive development,” Ebbin said. “We’re facing a shorter legislative session this year, and the administration’s support will make a difference on a bill that’s going to be complicated and have a lot of moving parts.”

Northam’s working group of staffers, led by Agriculture Secretary Bettina Ring, has been meeting with stakeholders from Virginia and other states since July. They are looking at ways to regulate the industry and its products, ensure public health and public safety, and oversee taxation.

Northam also said that the marijuana industry in Virginia must be equitable for minorities and small businesses and that there will be an effort to ensure those factors are considered when granting business licenses.

Health Secretary Daniel Carey said the state’s approach will also emphasize the collection of data to understand the impacts of marijuana use. He said Virginia will use lessons learned from other states, as well as from the tobacco and alcohol industries.

“Our goal is not . . . to encourage use but to make sure adults are making informed decisions,” Carey said.

A separate study commissioned this year by the state legislature and released Monday found that it would take two years and between $8 million and $20 million to set up a commercial marijuana market in Virginia and that it could ultimately generate $300 million in annual sales tax revenue.

According to the study by the Joint Legislative Audit and Review Commission (JLARC), over the past decade, law enforcement in Virginia has made between 20,000 and 30,000 marijuana-related arrests. Ninety percent were for possession of a small amount of the substance. Only 7 percent of those arrests resulted in a jail sentence.

Though Black and White Virginians use marijuana at about the same rate, JLARC found, Black Virginians are 3.5 times as likely to be arrested and convicted.

Looking at records from other states, JLARC found that decriminalization could be expected to reduce marijuana arrests by about 60 percent and that legalization would reduce them by 84 percent.

JLARC recommended that, should Virginia legalize marijuana, the government should not control sales as it does liquor.

No other state has a government-run marijuana industry, and creating one would provoke “an unknown federal response and potential lawsuits,” JLARC chief policy analyst Mark Gribbin told legislators at a presentation Monday.

Virginia lawmakers this year also barred police from using the smell of marijuana as the basis for a warrantless search. But only some cannabinoid products for specific medical purposes can be sold in the state.

Before the decriminalization legislation, local prosecutors who attempted to stop prosecuting people for possessing small amounts of marijuana faced resistance from police and judges who argued that doing so defies the law. Unlike in many other states, voters in Virginia cannot bypass the legislature with a statewide ballot referendum.

Four states voted to legalize recreational marijuana possession this year, including Republican-dominated South Dakota. Mississippi legalized medicinal cannabis. Across the country, in the past decade, 15 states and D.C. have legalized marijuana possession for any reason; 20 more allow medical use. And possession of small amounts of marijuana is no longer a crime across the border from Virginia in neighboring Maryland.

Under President Trump, targeting marijuana production and sales in states that have legalized the drug has not been a priority. But federal prosecutors continue to prosecute simple possession on federal land, including Northern Virginia’s George Washington Parkway. And a Justice Department official told a House panel this summer that Attorney General William P. Barr ordered staffers to investigate marijuana company mergers simply because of his “personal dislike” of the nature of their underlying business.

President-elect Joe Biden has endorsed decriminalization but not legalization, saying he wants more research into whether marijuana “is a gateway drug.”