The political war against the Second Amendment backfired spectacularly. Whenever politicians begin demanding another gun ban, Americans respond by buying the very firearms those politicians want to outlaw. Nothing empties a gun-store shelf faster than a politician promising prohibition. The United States already had 300 million privately owned firearms when Congress enacted the federal assault-weapons ban in 1994. That legislation followed several earlier federal restrictions imposed in 1989. Fear of further prohibition helped create waves of purchasing as Americans concluded, quite reasonably, that today’s lawful firearm might become tomorrow’s forbidden weapon. The 1994 federal assault-weapons ban was not permanent. Congress included a ten-year sunset provision, and the ban expired on September 13, 2004. Despite repeated demands from gun-control advocates, Congress declined to renew it. After ten years of experience with the law, Congress allowed it to expire rather than extend a...