Why MontanaFair Has a Prohibited Items ListMost of these rules exist for reasons that make sense once you think about them. Items Prohibited on the MontanaFair GroundsFirearms and Weapons: Firearms, knives, and other weapons are strictly prohibited on MetraPark grounds and inside all MetraPark facilities. First Interstate Arena Clear Bag Policy: The clear bag policy applies only to events inside First Interstate Arena, including MontanaFair Night Shows. Get our free mobile appFirst Interstate Arena Prohibited Items ListWe pulled together the full rundown of what's off-limits inside the First Interstate Arena specifically, so you can pack smart and skip the surprises when you attend one of the concerts. What You Can’t Bring to Events Inside the Arena at MontanaFair Before heading to any event inside the arena during MontanaFair, check this photo list of prohibited items that must stay home.