The Bank Secrecy Act's rules "apply very broadly," the officials said.

Just how someone registers with regulators depends on what they're doing. Commodity traders and financial institutions will have different expectations, for instance. However, it's really a question of who you talk to rather than talking to someone in the first place.

The move could help clear the air for investors and traders who've been looking for a firm government stance on the subject. Simultaneously, it's an explicit alert to those who might use cryptocurrencies to fund terrorism or other criminal operations. They could find themselves charged with financial crimes on top of any other offenses.