Between District of Columbia v. Heller (2008) and McDonald v. City of Chicago (2010), all Americans now have an individual right “to keep and bear arms” that neither the federal nor state governments may infringe. But these two cases, as important as they are, leave many questions open. What constitutes an infringement? The Court has said that the 2nd Amendment is not absolute. Then what are the precise limits that it places on gun control laws? Can the state restrict gun ownership only to citizens? Only to people with clean criminal records? Only to those who take gun safety courses? You may have a constitutional right to own a handgun—but presumably not if you are six years old or confined to a mental hospital. And how big can that handgun be? How many rounds can it hold? Can it be a fully-automatic machine-gun pistol? And what about other weapons? Are they protected “arms” that you can “keep and bear”? Only time—and many more cases—will tell.