(2) Like most rights, the Second Amendment right is not unlimited. It is not a right to keep and carry any weapon whatsoever in any manner whatsoever and for whatever purpose: For example, concealed weapons prohibitions have been upheld under the Amendment or state analogues. The Court’s opinion should not be taken to cast doubt on longstanding prohibitions on the possession of firearms by felons and the mentally ill, or laws forbidding the carrying of firearms in sensitive places such as schools and government buildings, or laws imposing conditions and qualifications on the commercial sale of arms. Miller’s holding that the sorts of weapons protected are those “in common use at the time” finds support in the historical tradition of prohibiting the carrying of dangerous and unusual weapons. Pp. 54–56.
...The Court also added dicta regarding the private ownership of machine guns. In doing so, it suggested the elevation of the "in common use at the time" prong of the Miller decision, which by itself protects handguns, over the first prong (protecting arms that "have some reasonable relationship to the preservation or efficiency of a well regulated militia"), which may not by itself protect machine guns: "It may be objected that if weapons that are most useful in military service – M16 rifles and the like – may be banned, then the Second Amendment right is completely detached from the prefatory clause. But as we have said, the conception of the militia at the time of the Second Amendment’s ratification was the body of all citizens capable of military service, who would bring the sorts of lawful weapons that they possessed at home."[46]