Overblown alarm over reasonable gun-control laws proposed in statehouses across the country has led to a movement by various local governments declaring themselves Second Amendment “sanctuaries” — vowing to establish local jurisdictions where state gun laws that they view as unconstitutional will not be enforced. These resolutions, to the extent they conflict with state law, lack legal effect: In Tazewell County, Va., for example, the “Sanctuary Resolution” approved by the board of supervisors purports to prohibit any county employee from enforcing, and any county funds from being used for the enforcement of, new state gun laws the county deems unconstitutional....