On Thursday the U.S. Supreme Court released an opinion in the most significant Second Amendment case since the right to bear arms was enshrined in the constitution. In  a 5-4 decision authored by Justice Antonin Scalia, the Court ruled that the Second Amendment protects an individual's right to bear arms, and the Court struck down the District of Columbia's draconian handgun ban.

Many U.S. citizens may be surprised to learn that for decades an academic debate has raged  over whether the right to keep and bear arms is a right held by individual citizens, or whether it is a collective right, predicated on service in a volunteer militia. The Second Amendment states: "A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed."

The U.S. Supreme Court has examined the Second Amendment only once, in 1939, when it ruled in United States v. Miller that a ban on sawed-off shotguns was not unconstitutional, as these weapons were unlikely to be used in 18th century militia service.  In addition to the individual right versus collective right debate is the question of what regulations are permitted under the Second Amendment.

Which brings us to yesterday's decision in District of Columbia v. Heller (07-290). The District of Columbia has one of the nation's most restrictive gun ownership laws. The law bans handgun possession by prohibiting the registration of handguns, prohibiting the carrying of an unlicensed handgun, and requiring residents to keep lawfully-owned firearms unloaded or disassembled in their homes, thereby preventing lawful gun owners from quickly responding to home intruders.

Dick Heller, a special police officer in D.C., applied to register a handgun and was refused by the District. He brought suit, challenging the District's long-standing regulation. The case eventually landed before the U.S. Supreme Court.

Much will be written of this decision in the coming days and years, but this was a huge victory for the rights of gun owners and those who wish to see the U.S. Constitution interpreted consistent with the Founders' intent.

In the case, the District of Columbia argued that the Second Amendment's prefatory clause - "A well regulated militia, being necessary to the security of a free state" - restricted the meaning of the operative clause - "the right of the people to keep and bear arms, shall not be infringed." In other words, militia service was the entire justification for the right to bear arms. The text does not identify, they argued, self-defense or hunting as the justification. As a result, the District argued the right to bear arms only exists in connection with militia service, and the amendment does not protect the individual right to bear arms.

Justice Scalia devoted much of his 64-page opinion to the meaning of the Second Amendment, and the opinion will serve as a treasure trove for academics and gun-rights advocates. "Logic demands," he wrote, "that there be a link between the stated purpose and the command." The prefatory clause in the Second Amendment serves as a clarification of the amendment's purpose. "But apart from that clarifying function, a prefatory clause does not limit or expand the scope of the operative clause."

Despite the amendment's prefatory reference to militia, Justice Scalia left no doubt as to the Court's position. "Nowhere else in the Constitution does a 'right' attributed to 'the people' refer to anything other than an individual right." Therefore, the Court started with "a strong presumption that the Second Amendment right is exercised individually and belongs to all Americans."

An argument was also floated (which Scalia characterized as "frivolous") that only those arms in existence in the 18th century are protected. Scalia pointed out that the rights protected in the Constitution are expansive and relevant even today. Just as the First Amendment protects modern forms of communication, the Second Amendment extends even to those instruments that did not exist at the time of the nation's founding.

With the question of whether the Second Amendment protects an individual right settled, the Court also addressed what sort of firearm regulations would be permissible. The Court seemed to acknowledge the validity of some restrictions when Scalia said, "nothing in our opinion should 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."

But Scalia distinguished the District of Columbia's handgun ban as "a prohibition of an entire class of 'arms' that is overwhelmingly chosen by American society for that lawful purpose. The prohibition extends, moreover, to the home, where the need for defense of self, family, and property is most acute."

Justice Scalia's opinion was joined by Chief Justice Roberts and Justices Thomas, Alito and Kennedy. Justice Stevens and Justice Breyer each filed a dissent, joined by Ginsburg and Souter.

The full impact of the Heller decision is yet to be seen. No doubt it will serve to forestall overzealous regulation of entire classes of firearms, and will be used to launch new challenges on other firearm restrictions.  But the decision serves as a powerful victory for original intent. As Justice Scalia wrote in his conclusion, "Undoubtedly some think that the Second Amendment is outmoded in a society where our standing army is the pride of our Nation, where well-trained police forces provide personal security, and where gun violence is a serious problem. That is perhaps debatable, but what is not debatable is that it is not the role of this Court to pronounce the Second Amendment extinct."