The U.S. Supreme Court ruled for the first time in history that the Second Amendment guarantees an individual right to keep a handgun in the home for self-protection. Through much of the 20th century, the Second Amendment had been viewed by the courts as protecting a collective right necessary to running state militias.

In a 5-4 decision in the case of District of Columbia vs. Heller , written by Justice Antonin Scalia, the court ruled the Second Amendment "guarantee(s) the individual right to possess and carry weapons in case of confrontation....The inherent right of self-defense has been central to the Second Amendment right." The court struck down two provisions of a District of Columbia law -- one a ban on handguns in the home and the other a requirement that any gun in the home have a trigger lock.

But the decision still permits many common gun regulations. Like other constitutional rights, the right to bear arms is not unlimited, Scalia wrote. The government still can enact laws making it illegal to carry concealed weapons or to possess automatic weapons, he said. And he added that the court's decision does not 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."

Missouri's law permitting people to carry weapons contains provisions that bar concealed guns in schools, churches and other places.

But the court's decision raises serious constitutional questions about laws in Chicago and surrounding communities. They have laws similar to the District of Columbia's handgun ban that the court struck down. The Illinois communities likely affected include Chicago, Evanston, Morton Grove, Oak Park, Winnetka and Wilmette. Beyond Illinois, the court's decision puts a cloud over laws in Toledo and San Francisco.

The court split down its usual ideological lines with the swing justice, Anthony M. Kennedy, joining the four more conservative justices to make a majority. Also in the majority were Chief Justice John Roberts and Justices Clarence Thomas and Samuel Alito. Dissenting were Justices John Paul Stevens, Stephen Breyer, Ruth Bader Ginsburg and David H. Souter.

Much of the 154 pages of opinions by the majority and dissenters was spent on the historical analysis of what the framers of the Second Amendment meant in the 18th century. Scalia said that the framers clearly were concerned that the federal government might try to disarm citizens, so the amendment protects their right to have a gun for self-protection. In his dissent, Stevens concluded that the framers were concerned about the federal government setting up a large standing army and adopted the amendment to underscore the importance of state militias.

In a separate dissent, Breyer argued that the District's law was reasonable because the prevalence of handguns in big cities is linked to higher levels of violence. He also said that the other provision of the District law struck down by the court -- one requiring guns in homes to be inoperable or locked -- was an important protection against accidental gun deaths that often involve children.

Scalia's opinion does not decide how broad of a right the court is recognizing. It does not determine, for example, what level of scrutiny the court will apply to gun regulations. In the First Amendment area, the court applies strict scrutiny, which means that almost all restrictions on First Amendment rights fail. It seems unlikely that high level of scrutiny will apply to the Second Amendment right in light of the laws that Scalia said would clearly pass muster.