The federal government says online gambling is a no-no. In the last few years, the Justice Department has made it very clear: You can't just open up an offshore casino online and start taking bets using actual money from the United States.

But last year, a couple of entrepreneurs asked themselves — what if you were only betting with Bitcoin?

"What Bitcoin does is that it totally circumvents that," says Jerry Brito, who studies the currency as part of his work as a senior research fellow at the Mercatus Center at George Mason University. "There is no Bitcoin company, there's no Bitcoin building that regulators can get their hands on. It's basically cash."