FinCEN told prosecutors that Samourai Wallet’s non-custodial model meant it likely did not meet the legal definition of a money transmitter.

Quotes that support claims

A mixer like Samourai that does not take custody of the cryptocurrency by possessing the private keys would strongly suggest that Samourai is not acting as an MSB.

FinCEN said that “because Samourai does not take ‘custody’ of the cryptocurrency by possessing the private keys to any addresses where the cryptocurrency is stored, that would strongly suggest that Samourai is NOT acting as an MSB [money services business].”