Industry reaction has been mixed since Attorney General Jeff Sessions rescinded Obama-era guidelines on enforcing marijuana laws Jan. 4. Some entrepreneurs express concern and fear, while others carry on with business as usual.

But one thing insiders agree on is the move will make it more difficult for cannabis companies to find and secure banking relationships, without which businesses are left with a ton of cash on hand.

Despite being legal for recreational or medicinal use in more than half the country, marijuana is still a Schedule I drug and therefore illegal at the federal level. In 2013, Barack Obama's administration issued the Cole Memorandum, which essentially directed federal law enforcement to allow businesses that are legal under state laws to operate. The memo also signaled banks could do business with these companies so long as they were in compliance with federal guidelines, although many have been hesitant.

In rescinding this policy, Sessions said future prosecutions of businesses and individuals who sell pot in states where it has been legalized will be left up to individual U.S. attorneys.

"The real sticking point here will be banking. Before, banks were very reluctant to do business based on the loosely defined Cole Memo," said Matt Karnes, founder of industry analyst firm GreenWave Advisors. "This raises more uncertainty, and I think there is going to be a pullback."

In a November 2017 report, GreenWave found that about 5 percent, or 368, of all financial institutions in the U.S. are on record with the Financial Crimes Enforcement Network (FinCEN), but only 1 percent are actually servicing these businesses. Many are credit unions and local and community banks. Karnes also said many marijuana businesses conceal the true nature of their business when establishing relationships, and once they are found out, the account is shut down.

"In the last report from FinCEN, 3,800 accounts were opened, but 3,700 were shut down. It's very short-lived," he said.

A report from Reuters Wednesday also indicated the action taken by Sessions came as a surprise to FinCEN, which was flooded with calls from banks on how to proceed. CNBC reached out to both the Department of Justice and FinCEN for comment but did not immediately receive a response.