Al Harrington who played 16 seasons in the NBA talks about entrepreneurship and his company Viola that is involved in the cannabis industry during the Legends National Basketball Retired Players Association Conference at Caesars Palace on July 9, 2019 in Las Vegas, Nevada.

Despite the sector's volatile state after a roller coaster 2019, former National Basketball Association forward Al Harrington continues to steer his fellow athletes to invest in cannabis while remaining patient on investment returns.

"What people have to understand is there is not a lot of profit in legal cannabis right now just because of the way its regulated, the tax structures and different things like that," Harrington said in an interview with CNBC. "But the one thing I tell them from a risk standpoint is – its prohibition."

"If you're going to be a part of something that will be around forever, and we're on the ground floor of pioneering the industry that I firmly believe will be bigger than the liquor industry and potentially bigger than the cigarette industry. And we know how big both those industries are. That's the risk, but the reward outweighs the risk."

Harrington, 39, made his rounds in Chicago, the site of the 2020 NBA All-Star Game, to promote his cannabis company, Viola. The company closed on a $16 million Series A funding round last October, adding new investors from ex-athletes, including former NBA players Josh Childress, Kenyon Martin, and Wilson Chandler.

Harrington, who grossed roughly $89 million in his playing career, played 15 seasons in the NBA, including two seasons with the New York Knicks.

His stance on the cannabis industry comes at a difficult time for the sector. The cannabis ETFMG Alternative Harvest ETF (MJ) is down 4.03% year to date and has dropped 37.41% over the past six months and took a 53.96% hit over the past year. ETFMG founder and CEO Sam Masucci blamed the initial excitement of the sector for its current decline, saying investors over-purchased cannabis companies.

"The prices of these companies get ahead of where they should be; they don't have the revenue to support it," Masucci said. "And so, the industry gets way overbought, and then it gets way oversold, which is exactly what you've seen in cannabis."

Unclear regulations in the U.S. have also contributed to the instability of the cannabis sector. Though some states -- like Nevada, California, Colorado, and now Illinois, which grossed over $19 million in sales the first 12 days recreational cannabis was eligible to purchase -- have legalized cannabis, there is no clear sign when it could be federally regulated like in Canada, which is where many companies in the ETFMG Alternative Harvest ETF are based.

But as more states like New Jersey (which expects $210 million in state tax revenue from cannabis sales, according to the New York Times) and New York (which projects $772 million in tax revenue) get closer to the legalization of cannabis, a federal bill may gain more momentum. The 2018 Farm Bill has already legalized CBD derived from hemp plants and contains no more than 0.3% THC; hence, some form of cannabis is already legal.

"The train's left the station," Masucci said. "People are using it whether it's just straight CBD, hemp derived [or] THC in states where it's approved."

Like Harrington, BioSteel Sports Nutrition Inc. founder Michael Cammalleri is also advising former players to research cannabis. Understanding the proper regulatory environment surrounding cannabis will help fuel investment returns.