The Obama administration has sent a message to the nation's bankers: Even though the sale of marijuana is a federal crime, they can provide service to this new industry without fear of prosecution, but only if the bankers follow a detailed list of guidelines. Many praised the move as giving financial institutions "the green light" to finally serve the multibillion dollar cannabis industry. But the nation's bankers don't see it that way. They say the guidance from the Department of Justice and the Department of Treasury doesn't change the fact that possession or distribution of marijuana violates federal law, and any bank that supports those illegal activities could be prosecuted or sanctioned. (Read more: US issues new rules on banks and legal marijuana)

The Colorado Bankers Association called the guidance a red light. The association's senior vice president, Jenifer Waller, said the government outlined "all the risks involved of banking the marijuana industry" and "made it very clear that financial institutions can still face criminal liability." Waller told CNBC financial institutions in Colorado would like to service the legal marijuana industry in that state, but she does not know of a single one that changed its position as a result of the federal memos released last week. "Operating on a memo that is in conflict with the law is just unwise for any business, including financial institutions," Waller said. Jim Pishue, president of the Washington Bankers Association, points out that guidelines don't supersede federal law, which categorizes marijuana as a controlled substance that cannot be legally sold anywhere in the U.S. And guidance, he noted, can change at any time. "The guidelines may give some a little bit of confidence, but I don't think it will give them enough to bank these folks," Pishue said. The National Cannabis Industry Association believes it's too soon to know what effect the new guidance will have. The association has praised the feds for providing a roadmap for financial institutions that want to work with legal marijuana businesses. "We don't need every bank in America or even every bank in Colorado and Washington to suddenly start offering accounts to our businesses," said Deputy Director Taylor West. "I think there will be some very smart banks and credit unions that will recognize that this is a potentially valuable new industry for them." And that may happen—eventually.



Steve Hudak, spokesman for the Financial Crimes Enforcement Network at the Treasury, told CNBC that in preparing its guidance, the agency learned that there are financial institutions interested in accepting this business. "Let's give it some time and see if they come forward," Hudak said. "We tried to make it clear that financial institutions can offer services to these businesses and still comply with their obligations under the Bank Secrecy Act." And here's another sign that big banks don't want to touch this business: Wells Fargo and FirstBank have decided not to refinance commercial loans to landowners who lease to marijuana businesses. The banks told The Denver Post that this property, when used as collateral, could be seized under federal drug laws. Who will be first? Some have suggested that small community banks may be the first to step up to the plate because the revenue from marijuana businesses would be more significant for them. Karen Thomas, senior executive vice president for government relations and public policy at the Independent Community Bankers of America, said most of its members still feel it's too risky to take the plunge. Another stumbling block: The new guidelines require a lot of paperwork and due diligence to satisfy federal regulators and prosecutors. "And that due diligence is still very burdensome and prohibitive," Thomas said. "It's very compliance intensive and risky if the bank misses something." For example, the Justice Department would expect a bank to make sure any marijuana business with an account did not sell pot to minors, is not involved in illegal activities and that the cash flow of that business is what would be reasonably expected. In addition to all the monitoring, the bank would have to file suspicious activity reports with the federal government anytime there was a cash transaction of $10,000 or more. (Read more: Pot of gold? Cannabis-infused soda and lotions) "Those are things that are very difficult for a bank to be confident enough about to go ahead and provide the banking service," Thomas said. "I think those hurdles are just too great to overcome."

The pitfalls of a cash-only business Licensed and regulated pot shops are doing a booming business in Colorado after voters approved recreational marijuana use. The first retail stores are expected to open in Washington this summer. Customers must pay in cash—no checks, no credit cards and no debit cards. The cannabis industry in the U.S. is a cash-only business, with all the problems that creates. A busy pot shop in Denver can handle about $25,000 a day. "It's crazy," said Brian Ruden, who owns Starbuds in Denver and runs his business on cash and money orders. It's not only "extremely inconvenient," but it creates a security nightmare. "We have secured rooms, and within those secured rooms we have secured locking safes and sometimes within those safes we have money safes," Ruden said. "That won't stop someone from coming in and trying to rob us." John Davis, who owns Northwest Patient Resource Center, a medical marijuana facility in Seattle, plans to meet with a bank next week to see if it is willing to take his business. He calls the banking situation in his industry "frustrating and ridiculous." Because his customers can't pay with a check or credit card, Davis bought an ATM for his lobby, and he stocks it with cash every day. "You need a bank to pay taxes, to pay vendors and to pay employees," Davis said. "Without a bank you have to keep the cash on site, and people realize this and that can make you a target for theft." Calls for Congress to act The financial industry will need more than a few signals from the White House that it's safe to bank legal marijuana businesses. Bankers and those in the expanding legal marijuana business want Congress to change the law—to make it clear that it's not a crime to provide financial services to the legal marijuana businesses.