The Streamline is a free bus service in and around Bozeman. According to it’s rules:

No firearms, not even a pocket knife.

How can they get away with this? Aren’t Montana localities prohibited from enacting their own gun control laws?

Streamline is not a service of any government. It’s provided for free by HRDC, a non-profit corporation. As such, they are not bound by the restrictions on localities and can prohibit whatever they’d like on their own property.

An obscure (#13) rule on a website probably doesn’t meet the requirements of “expressly” as required by law. But if they spot you, they can ask you to get off the bus. You’d then be stuck who knows where.

Don’t give them your business. Even though it’s free, the cost is too high.