Sam Walsh, left, a budtender, and facility manager David Martinez set up marijuana products as the 3-D Denver Discrete Dispensary prepares to open for retail sales on January 1, 2014 in Denver, Colorado.  - 

Several states have legalized marijuana, even though the federal government still considers it an illegal drug. Well, a problem is banks are reluctant -- in most cases unwilling -- to do business with the marijuana industry.

Banks worry doing that could subject them to prosecution from the feds, for racketeering or money laundering or aiding and abetting criminal activity.

"The banks have come to the conclusion that the risks are just too great," says Robert Rowe, senior counsel for the American Bankers Association. "Marijuana is still illegal as far as federal law is concerned, and banks are subject to federal law."

Not having access to banks is hard for growers and dispensaries in states where pot is legal.

"You know, it is hard to buy things, it is hard to pay your employees, it is hard to really go about business," says Bill Piper, with the Drug Policy Alliance.

On top of that, it isn't safe when all your business is done in cash. Attorney Genreal Eric Holder made that point yesterday, at an event at the University of Virginia. He said the government is working on new guidance. Dan Riffle, with the Marijuana Policy Project, hopes it will be comprehensive.

"Well, there is a big legal distinction -- for banks, especially, between we're not going to prosecute this crime and we don't consider this a crime."

After all, the Justice Department could reverse a decision not to prosecute banks at any time.

Follow David Gura at @davidgura