DENVER (AP) — Medical marijuana is legal in 17 states, but the industry has a decidedly black–market aspect — it's mostly cash–only.

Banks won't touch pot money. The drug is illegal under federal law, and processing transactions or investments with pot money puts federally insured banks at risk of drug–racketeering charges.

In Colorado, state lawmakers are attempting an end–run around the federal ban with a bill that would create the nation's first state cooperative financial institution for dispensaries and growers to allow them to store and borrow money.

But the marijuana co–op proposal faces big obstacles. Any marijuana money is subject to federal seizure, even when it's legal in a state and part of a state agency. Other marijuana states are watching to see whether Colorado succeeds in sidestepping federal banking obstacles.