John Boehner is well-known for his fondness for red wine and cigarettes. But in his new career since retiring as House speaker, the veteran Ohio GOP lawmaker has added marijuana -- or at least the industry -- to his list of vices.

In a striking scene, the ex-speaker on Tuesday made a public pitch for why Americans should invest in the growing marijuana market.

In a webcast launching the National Institute for Cannabis Investors, Boehner – once a strong opponent of legalizing marijuana – said that now is the time to invest in the cannabis industry as lawmakers on Capitol Hill, including some conservative leaders, are beginning to change their views on legalization. He said nationwide legalization could happen within a matter of years.

“I’m all in,” Boehner said. “This is the time to go all in on cannabis.”

In regards to legalization across all 50 states, Boehner said: “It’s not a matter of if, it is a matter of when.”

Earlier this year, Boehner joined the advisory board of multi-state marijuana company Acreage Holdings, even though he said in 2011 that he was “unalterably opposed” to legalizing the drug. He voted against legalizing medical marijuana in Washington, D.C. in 1999.

As recently as 2015, Boehner came out against reclassifying marijuana under federal law, which currently considers marijuana as having no significant medical value, saying he was "concerned that legalization will result in increased abuse of all varieties of drugs, including alcohol."

Boehner said that his views on marijuana changed after he spoke with a former Navy SEAL who used cannabis to treat the migraines he suffered from after being injured in combat.

“He started using cannabis and the migraines disappeared,” Boehner said. “That’s when I realized I was wrong.”

A Pew Research Center poll from October shows that approximately 60 percent of Americans support legalizing marijuana, compared with 31 percent in 2000. Far more Democrats than Republicans back the measure.

Nine states, plus the District of Columbia, permit the recreational use of marijuana.

Marijuana, however, remains illegal under federal law, and Attorney General Jeff Sessions has rolled back Obama-era protocols that discouraged criminal prosecution of medical marijuana dispensaries. The move effectively unleashed federal prosecutors to consider bringing marijuana cases, while stopping short of ordering them to do so.

Despite Sessions’ rollback, Boehner said he has found an ally for legalization in the Oval Office.

“While I don’t want to give away too much of my conversations with President Trump or I won’t be having those conversations anymore,” he said, adding, “But President Trump said, ‘I agree with Boehner, he’s right.’”

Boehner -- who appeared in the webcast besides Danny Brody, who spearheaded two major cannabis IPOs, and investment publisher Mike Ward -- said there are three big roadblocks to the growth of the cannabis industry: marijuana being classified as a Schedule I drug, banking regulations on cannabis companies and an IRS code that doesn’t allow these companies to deduct normal expenses from their taxes.

The former House speaker, however, said he was confident the banking regulations and the IRS code could be changed and added that downgrading marijuana is being discussed in Congress.

Marijuana is currently grouped with heroin and LSD as a Schedule I drug, while drugs like cocaine and methamphetamine are Schedule II. Cannabis activists point to research on its medical uses as a reason to downgrade marijuana to Schedule V alongside cough suppressants and some anticonvulsants.

Fox News' Gregg Re contributed to this report.