Nelson Lund is a professor at George Mason University School of Law.

McDonald holds that the Second Amendment right to keep and bear arms, recognized in Heller two years ago, is protected against infringement by state and local governments. The holding was virtually dictated by any honest reading of the Court's substantive due process precedents, and a plurality of four Justices reached this unsurprising conclusion.

The most interesting aspect of the decision is Justice Thomas' concurrence, which rejects the plurality's reliance on the judicial fiction of substantive due process. Thomas relies instead on the original meaning of the Privileges or Immunities Clause. His opinion is scholarly and judicious, and it cements his standing as the only Justice who is more than a half-hearted originalist. Thomas confines himself to the issue presented, which involves only the right to keep and bear arms, and explains why stare decisis should not foreclose an originalist approach in this case. With appropriate judicial restraint, he declines to decide in advance exactly what implications his analysis may carry with respect to substantive due process precedents involving other provisions of the Bill of Rights.

One question raised by the disagreement between the plurality and Thomas involves the rights of noncitizens to keep and bear arms. The Due Process Clause (on which the plurality relied) applies to all "persons" while the Privileges or Immunities Clause (on which Thomas relied) protects only "citizens." Thomas prudently declines to speculate on what difference this may make in future cases.

The plurality is not so restrained. They reaffirm a number of irresponsible dicta in the Heller opinion that endorsed various gun control regulations that were not at issue in either case. Those dicta, however, still leave many important questions unanswered. Here are some examples:

Heller endorsed bans on the carrying of concealed weapons, but said nothing about a right to carry weapons openly. Because the Second Amendment expressly protects the right to "bear" arms, as well as the right to "keep" arms, the text of the Constitution seems inconsistent with allowing the government to forbid both open and concealed carry of weapons. Such a ban would also be inconsistent with Heller's emphasis on self-defense as the core of the Second Amendment right: most people are in much more danger of encountering dangerous criminals outside their homes than within them. But the issue remains open in the courts.

Similarly, Heller endorsed bans on carrying weapons in "sensitive places," but articulated no test for identifying such locations, beyond a mention of government buildings and schools. McDonald reaffirms this dictum but offers no further guidance, so the lower courts will for now apparently have to develop a "sensitivity jurisprudence" on their own. Is a university campus more "sensitive" than a shopping mall across the street? Is a government-owned cabin in a national forest more "sensitive" than a privately owned hotel on a busy urban street? These and countless similar questions will be open to litigation.

State and local jurisdictions, moreover, sometimes place very onerous administrative obstacles in the path of those who desire to keep or carry firearms. Such obstructionism may become more intense in those jurisdictions that would like to impose outright gun bans that the courts will no longer uphold. Courts will surely face numerous challenges from citizens who claim that such administrative obstacles impermissibly burden the underlying substantive right, and it is not yet clear how such challenges will be resolved.

How the courts respond to the issues left unresolved in Heller and McDonald may be the most important factor in determining whether the Supreme Court's budding recognition of the constitutional right to arms will have much practical significance in American life.

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