In "The Standardless Second Amendment," Tina Mehr, an attorney fellow at the Los Angeles County District Attorney's Office, and Adam Winkler, a professor of law at UCLA School of Law, note, "Traditionally, the Supreme Court articulates a standard of review for lower courts to apply to laws burdening fundamental rights."
But in D.C. v. Heller, where the Supreme Court found that owning a gun is an individual right protected by the Second Amendment, and then held that the right applies to the states in McDonald v. Chicago, the high court "declined to establish a clear standard or test for the Second Amendment," they write.
Since Heller and McDonald, lower federal courts have dealt with more than 200 cases challenging gun control regulations, and while the courts methods for interpreting the laws have varied, most have been upheld as "public safety exceptions," that do not violate the Second Amendment, Mehr and Winkler write.
But as the authors note, Justice Stephen Breyer's dissent in McDonald includes a prescient observation. Breyer predicted confusion among the federal courts, writing, "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?"