As a measure of the gun culture’s dangerous sway over statehouse politicians, it is hard to top the pending proposal in Missouri that would pronounce all federal gun safety laws null and void in the state and allow the arrest of federal agents who try to enforce them.

This bizarre legislation, which Republican majorities hope to enact Sept. 11, would override an earlier veto by Gov. Jay Nixon, a Democrat, who noted the obvious fact that the measure is unconstitutional according to precedents stretching all the way to the Civil War.

But the bill’s proponents care little for legal niceties, or for the near-certainty of an adverse court ruling against their hoary states’-rights gambit. Dusting off the polemics of nullification, the supposed “law and order” politicians in Jefferson City would rather support an unconstitutional measure than set a law-abiding example of government responsibility.

No less regrettable is that they are hardly alone in their obeisance to the gun lobby. Horrendous spates of gun violence have prompted six states to enact stronger gun safety laws in the last year. But a score of other statehouses have weakened existing laws, in particular loosening gun laws regulating the “open carry” of firearms, inviting public flaunting of weaponry.

In a particularly egregious display of insensitivity and arrogance, cocky celebrants of gun rights packed their weapons openly and legally this month on the streets of Newtown, Conn., where a shooter gunned down 20 schoolchildren and six adults last December. Similarly swaggering gun enthusiasts showed up this summer in Aurora, Colo., to protest new gun controls even as residents were commemorating the 12 people killed and 70 wounded last year when a gunman invaded a movie house.

Too many politicians — in Congress and elsewhere — prefer to blindly salute the Second Amendment rather than face the appalling costs of gun mayhem in communities like Aurora, where the toll so far — apart from the loss of life — is $17 million and counting for the needs of survivors, according to a conservative estimate in the Denver Post.

The Obama administration, meanwhile, has been left to issuing limited executive orders that nevertheless highlight the depth of the problem. One will limit the return of American battlefield weapons that have been flooding the country; another stops the practice that lets felons and domestic abusers obtain arms by registering them through corporations and trusts. These gestures are modest compared with the overwhelming need for broad federal legislation.