Without getting too far into the .... wait for it ..... "WEEDS!" state-chartered banks have some flexibility to work with "legal" pot distributors and in fact do in the various legal states. The Obama DOJ put out a memo called the "Cole Memo" that explained some compliance steps that would avoid scrutiny under BSA/AML laws which most follow. There is some confusion over its validity since the election, but neither DOJ nor the Fed (who regulates state-chartered banks at the federal level) has taken action and all seem to agree that these businesses should be able to bank their money. There are detailed compliance procedures that a bank wishing to enter that business needs to put in place, but it's not rocket science and lots are doing it.