One of the oldest and most basic rights guaranteed by the Constitution is the right of American citizens to travel from one state into another state. The Supreme Court has repeatedly held that states are forbidden from interfering with this right by treating nonresidents and new arrivals less favorably than their own citizens. But the Commonwealth of Massachusetts forbids nonresidents from carrying a firearm for self-defense on pain of a felony conviction and a minimum of eighteen months in prison—even though the Constitution protects the right of all Americans to carry arms outside the home for self-defense.

Philip Marquis and Dean Donnell are both residents of New Hampshire, where they are legally permitted to possess firearms. In two separate incidents, Marquis and Donnell each drove into Massachusetts and were involved in motor vehicle accidents. In both instances, the Massachusetts police learned that the New Hampshire driver had a firearm in his car, and the Commonwealth of Massachusetts decided to prosecute Marquis and Donnell for being in possession of a gun without a Massachusetts license.

Because Marquis and Donnell are not residents of Massachusetts, Massachusetts law only permits them to acquire a temporary firearms license “for the purposes of firearms competition.” Massachusetts law does not allow nonresidents to be issued a license to carry for self-defense—even though the Supreme Court has held that the right to bear arms for the purpose of armed self-defense is the “central component” of the Second Amendment, and that this includes the right to bear arms outside the home. Accordingly, the district court judge dismissed the charges against Marquis and Donnell as violating the Second Amendment. The Commonwealth appealed the case to the Massachusetts Supreme Judicial Court.

The Cato Institute filed an amicus brief with the Massachusetts Supreme Judicial Court in both cases, urging it to affirm the order of dismissal. Our brief focuses on three important points.

First, we explain that the Constitution protects the right of Americans to engage in interstate travel without interference by the states. Citing a long list of cases going back to the early 19th century, we show how the Supreme Court has always held that the right to engage in interstate travel is a privilege of American citizenship that states cannot punish, obstruct, or discourage—even through indirect methods. We also explain how the Court’s failure to fully uphold the right to interstate travel tragically helped to entrench the abuses of Jim Crow, whereas the judicial protection the right of interstate travel in the 1960s helped the Civil Rights Movement bring an end to that oppressive system.

Second, we explain that the right to armed self-defense is a privilege of American citizenship that the Fourteenth Amendment was intended to secure for all Americans—and especially for newly freed former slaves after the Civil War. Tragically, the Supreme Court’s failure to uphold this right led to the persistent disarmament of African-Americans in the South, where they were unable to defend themselves against the tyranny and oppression of white supremacists.

Finally, we point out that even today interstate travel can be dangerous, and the need for self-defense is at its highest outside of the home. We provide harrowing examples of Americans who have been attacked—and tragically, even killed—when traveling from one state to another. In these situations, having a gun can be the difference between life and death.