MRS 21.760.2
2. No county, city, town, village, municipality, or other political subdivision of this state shall adopt any order, ordinance or regulation concerning in any way the sale, purchase, purchase delay, transfer, ownership, use, keeping, possession, bearing, transportation, licensing, permit, registration, taxation other than sales and compensating use taxes or other controls on firearms, components, ammunition, and supplies except as provided in subsection 3 of this section.
But, they aren't making any orders, ordinance, or regulation, except as provided by the state statutes. The ability for political subdivisions to make their facilities off limits to guns is provided for in RSMo 571.107.1.(6) as we already discussed. Also, the ability to make private property off limits is in 571.107.1.(15).
Still, the oddball prohibitions are in effect, where violating the law carries no punishment, unless you're really stupid.