Denver businessman Kayvan Khalatbari operates a real estate holding company, consulting firm, several pizzerias and the second-oldest medical marijuana dispensary in Colorado.

"I moved here from my hometown of Lincoln, Nebraska, a decade ago and I've had the fortune of having a front row seat in the evolution of the cannabis industry," said Khalatbari, who co-founded Denver Relief in 2009. "Unfortunately, I've also had the misfortune of being caught in the middle between state and federal laws, banking laws, tax laws and insurance laws that can't seem to get on the same page."

Over the past five years, the former engineering student has turned his budding business into a profitable, tax-paying venture, he said. Yet, like many owners of the more than 2,300 licensed medical marijuana centers in the U.S., Khalatbari has hit a brick wall when it comes to banking.