though i personally dont like drugs it has to be said
although a state may allow drugs to be sold by retailers legally[in certain states]. the bank is not state owned. most banks would still trat weed as illegal because their regulation is based on another state/nation/international law.
it has already been shown that weed retailers have had trouble getting access to a bank account due to the banks national/international AML/KYC policies.
http://uk.businessinsider.com/americas-marijuana-companies-cant-put-money-in-banks-2015-11Though this is all completely legal [in state] revenue, most banks won't take cannabis cash.
That's because marijuana is illegal under US law, and banks have to comply with federal regulations. While it's possible for banks to accept pot cash without violating federal law, they have to take many additional steps to ensure they're in compliance.
Rob Rowe, the Vice President of the American Bankers Association, told the Huffington Post in April that if banks do choose to process funds from marijuana companies, and something turns out wrong, the bank will risk losing its charter.
For many banks, it's not worth it. Just 220 of America's 7,600 banks and credit unions accept money from pot businesses, Bloomberg reported in October[2015]. Effectively, this means legal pot is a cash-only business.
so bitcoin will actually benefit these weed retailers as a method to store value securely instead of hiding it under the mattress.