FinCEN

The Financial Crimes Enforcement Network (FinCEN) is part of the US Treasury. It collects reports about suspicious money flows from banks and other financial firms and uses them to chase money laundering, terrorist financing and fraud.

For crypto, FinCEN's big move came in 2013, when it said businesses that exchange or transmit crypto for customers generally count as money services businesses. That pulled exchanges under anti-money-laundering rules: register, check customer identities and report suspicious activity.