However, the U.S. Constitution does not prohibit states (or pseudo-states, in the case of Washington, D.C.) from enacting their own restrictions. That was the whole point of the Ninth and Tenth Amendments.
Dr. Kevin Gutzman agrees:
The original understanding of the Bill of Rights, including the Second Amendment, was reflected in the Bill's preamble. That preamble says that the Bill of Rights was added to the Constitution "in order to prevent misconstruction or abuse of its [that is, the federal government's] powers." It was not about empowering federal judges to strike down state laws, in other words, but about limiting federal power.Thank you, Dr. Gutzman. We need more constitutional originalists like you.
The Supreme Court reflected this understanding in the 1833 case of Barron v. Baltimore (1833). There, for a unanimous Court, Chief Justice John Marshall said that the Bill of Rights limited only the powers of the federal government, not those of the states. This was the only significant decision in which Marshall came out for a limitation on federal power; he did so because what he was saying was indisputable.
One might counter by saying that the District of Columbia is part of the federal government. Yet, Congress long ago delegated home rule functions to D.C., and it allows residents to elect mayors, city councilors, and a delegate to Congress. When it comes to the Second Amendment, then, D.C. is a state, and the Second Amendment does not restrict its policy-making discretion.
This is not to say that gun control laws are a good idea. It also does not mean that D.C. residents do not have a right to keep and bear arms. What it means is that if they want that right to be respected, people in D.C. should take that up with their own government, not end-run the republican process by trying to get the Court to overturn its valid laws.
If the conservative majority on the Supreme Court rules in favor of Mr. Heller and against the D.C. gun laws, it will be ruling against the original understanding of the Second Amendment.
It's one thing to defend the right to keep and bear arms, but it should not be done at the expense of states' rights. After all, that was one of the principles the Second Amendment was designed to protect.