That's a really good point. I wonder if the state isn't already effectively outsourcing penal law to financial institutions – since the closure of an account is effectively a penalization, and in the case of AML without due recourse for the consumer – and what laws/legal exceptions would govern the export of government duties to private institutions.  

 I'm not a lawyer (not legal advice) but I can guess the BSA has already been challenged on constitutional grounds resulting in a loss for the plaintiffs. again, not a lawyer and can't say for sure.