Attorney General Jeff Sessions created a wave of worry among pro-marijuana groups this week when he said he doesn't think the United States is a better place with "more people smoking pot."

"I am definitely not a fan of expanded use of marijuana," Sessions said Monday. "But states, they can pass the laws they choose. I would just say, it does remain a violation of federal law to distribute marijuana throughout any place in the United States, whether a state legalizes it or not."

Sessions' comments paralleled those of White House Press Secretary Sean Spicer, who said last week that states with legalized recreational marijuana use will see "greater enforcement" of federal laws.

That could be a problem with the eight states and the District of Columbia that have legalized marijuana for recreational use. Another 28 states plus D.C. allow medical marijuana.

The Marijuana Majority is worried that the Trump administration is going to reverse President Trump's campaign pledges to respect states' marijuana laws.

"Reversing course would be an incredibly unpopular move and a huge distraction from the rest of the White House's agenda. This is a fight they should not want to pick," Tom Angell, founder and chairman of the marijuana organization, told the Washington Examiner.

The Marijuana Majority currently has a petition urging the Trump administration to keep such campaign pledges. Angell noted that states are showing the benefits of legalizing recreation marijuana, including "generating revenues, creating jobs and reducing crime."

"The Justice Department should uphold President Trump's campaign pledges to let these voter-approved laws be implemented without federal interference," Angell added.

According to the Marijuana Business Factbook 2016, the cannabis industry is forecast to pump from $24 billion to $44 billion annually into the country's economy by 2020.

But, cannabis remains a Schedule I illegal drug under federal law. And that, according to John Hudak, is a real roadblock to more economic growth in the field.

Sessions has "a tremendous amount of enforcement at his hands" as AG, an expert on marijuana legalization and governance at the Brookings Institution told the Washington Examiner.

"Every single person in the cannabis industry is committing a federal offense," Hudak explained. He added that Sessions' range of options of what he can do in terms of marijuana enforcement is "innumerable."

For example, federal prosecutors could file injunctions against states that have legalized marijuana, Hudak said. State and local governments that disagree with their own marijuana policies can also pair with the federal government to enforce federal law.

"I am certain marijuana enforcement [under Trump] will not be identical to what it was under [former President Barack] Obama," Hudak said.

The National Cannabis Industry Association concedes that though the drug is still illegal under federal law, there is good reason why states have been legalizing it.

Taylor West, deputy director of the only marijuana trade association, told the Washington Examiner that Sessions' comments linking violence and drug cartels to marijuana are the most concerning.

"This is the exact argument for bringing marijuana out of the illegal market," West said, explaining that states that have legalized the drug have actually seen a reduction in violence now that the market is no longer legal.

Legalizing marijuana at the state level gives the government "the ability to put controls on the industry," West said. "It is a highly regulated, highly integrated industry," now compared to years ago, she explained.

Studies have found there is no correlation between legalizing marijuana and rising violent crime rates.

As for the NCIA, West says they are preparing for all the possibilities and "also continuing to work hard to remind the Justice Department that it's not just us — there are lawmakers at every level who believe strongly" in marijuana initiatives.