Two years ago, the Supreme Court struck down parts of the District of Columbia’s gun-control law. On Tuesday, the court will consider whether that decision should apply everywhere in the country, not just in the federal territory of the nation’s capital.

We disagreed strongly with the 2008 decision, which took an expansive and aggressive view of the right to bear arms. But there is an even broader issue at stake in the new case: The Supreme Court’s muddled history in applying the Constitution to states and cities. It should make clear that all of the protections of the Bill of Rights apply everywhere.

McDonald v. Chicago is a challenge to a law that makes it extremely difficult to own a handgun within Chicago’s city limits. The challengers rely on the court’s 5-to-4 ruling in 2008, which recognized an individual right under the Second Amendment to carry guns for self-defense. But that decision left open an important question. The Bill of Rights once was largely thought to be a set of limitations on the federal government. Does the right to bear arms apply against city and state governments as well?

Since states and localities do far more gun regulation than the federal government, the court’s answer will have a powerful impact. The United States Court of Appeals for the Seventh Circuit, in Chicago, relying on 19th-century precedents, ruled that the Second Amendment does not apply to states and cities.