This cannot be overemphasized. I'm not libertarian enough to believe that no laws should be made "merely" to promote an orderly society, rather than only to protect individual freedom. But many "common sense" laws are simply silly. As a matter of common sense a gun shop owner should ensure that he's not hiring felons. But it should be a matter of good business sense, not law. And if there are any adverse consequences from a felon deceiving a gun shop owner the penalty should fall solely on the felon.