[Aguila Blanca]

Not a lawyer, but IMHO a federal law is not "unconstitutional" if a county sheriff says so, or because a county board of commissioners says so, or because the Missouri state legislature says so. A federal law is unconstitutional only when the federal judiciary says it is unconstitutional.

These types of "sanctuary" laws are, IMHP, dangerous, because gullible people may actually believe they offer defense/protection for engaging in illegal activities. These laws are political grandstanding. They are pretty much reverse virtue signaling.