America is reaching a "tipping point" in marijuana legalization that could eventually spur a national change by the next midterm election, pot investor Paul Rosen told CNBC Wednesday.

"There's sort of an irrevocable momentum towards sensible cannabis reform, which ultimately should lead towards a harmonization of federal and state laws," the founder of Breakwater Venture Capital said on "Power Lunch."

Michigan, where voters passed medical marijuana laws 10 years ago, is the latest to join the circle of 10 states and Washington, D.C., that have legalized weed for recreational use. Voters in Utah and Missouri also relaxed their laws to allow medical marijuana in Tuesday's midterm election.

"Individually, it's just another data point that suggests that the desire for sensible cannabis reform at a state and a citizen level is enhancing in every election season," said Rosen, former CEO of PharmaCan Capital, which later became Cronos Group.

However, voters in North Dakota, where medical marijuana is legal, declined legalizing the drug for recreational use Tuesday. And weed is still illegal federally, which presents a host of other challenges for the budding pot industry.

But cannabis stocks are rising on hopes that more help for further reform could be on the way in the near future.

After losing most of their gains from Wednesday's premarket, shares of Tilray, Canopy Growth, Aurora Cannabis, Cronos Group and Aphria spiked after a surprise ouster of Attorney General Jeff Sessions, who opposes legalization.

In addition, the incoming Democratic-controlled House could be more favorable to relaxing federal laws, and a record number of Americans support legalization, a Gallup poll shows.

"What will presage that breakout event will be a series of incremental steps, such as the states' acts passing," Rosen said.

"As to when that seismic event … will resolve the dichotomy between federal and state law, my own feeling is that it's going to happen post-2020 and close to the next midterm in 2022," he said.

Correction: This article has been updated to clarify that Paul Rosen is former CEO of PharmaCan Capital, which later became Cronos Group.

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