Dissenting from yesterday's Supreme Court ruling that said the Second Amendment applies to the states via the 14th Amendment, Justice Stephen Breyer complained that judges will now have to make assessments about gun control for which they lack the necessary expertise. To illustrate that point, he posed a series of rhetorical questions (emphasis added):

Does the right to possess weapons for self-defense extend outside the home? To the car? To work? What sort of guns are necessary for self-defense? Handguns? Rifles? Semiautomatic weapons? When is a gun semi-automatic? Where are different kinds of weapons likely needed? Does time-of-day matter? Does the presence of a child in the house matter? Does the presence of a convicted felon in the house matter? Do police need special rules permitting pat-downs designed to find guns? When do registration requirements become severe to the point that they amount to an unconstitutional ban? Who can possess guns and of what kind? Aliens? Prior drug offenders? Prior alcohol abusers? How would the right interact with a state or local government's ability to take special measures during, say, national security emergencies?

Most of these are questions that courts may actually have to address. But I doubt they will be called upon to settle the issue of what constitutes a semiautomatic weapon (a gun that fires one round, ejects the empty casing, and automatically loads a new cartridge when the trigger is pulled) or decide whether people have a right to possess them (a question the Court already answered in District of Columbia v. Heller, where it overturned a law that banned semiautomatic handguns). I suspect Breyer is using semiautomatic weapon as a synonym for assault weapon, an arbitrary category that is based mainly on the proscribed guns' military-style appearance rather than their capabilities. While this conflation demonstrates Breyer's point that judges do not necessarily have the knowledge to assess the wisdom or propriety of gun control laws, the same is true of legislators. Judges, like legislators, can and should strive to intelligently assess the evidence and arguments submitted by both sides. Sometimes judges and legislators both fail at this task.