The court had not conclusively interpreted the Second Amendment since its ratification in 1791. The amendment reads: "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 basic issue for the justices was whether the amendment protects an individual's right to own guns no matter what, or whether that right is somehow tied to service in a state militia.
Writing for the majority, Justice Antonin Scalia said that an individual right to bear arms is supported by "the historical narrative" both before and after the Second Amendment was adopted.
The Constitution does not permit "the absolute prohibition of handguns held and used for self-defense in the home," Scalia said. The court also struck down Washington's requirement that firearms be equipped with trigger locks or kept disassembled, but left intact the licensing of guns.
Scalia noted that the handgun is Americans' preferred weapon of self-defense in part because "it can be pointed at a burglar with one hand while the other hand dials the police."
Scalia's opinion dealt almost exclusively with self-defense in the home, acknowledging only briefly in his lengthy historical analysis that early Americans also valued gun rights because of hunting.
The brevity of Scalia's treatment of gun ownership for hunting and sports-shooting is explained by the case before the court. The Washington law at issue, like many gun control laws around the country, concerns heavily populated areas, not hunting grounds.
In a dissent he summarized from the bench, Justice John Paul Stevens wrote that the majority "would have us believe that over 200 years ago, the Framers made a choice to limit the tools available to elected officials wishing to regulate civilian uses of weapons."
He said such evidence "is nowhere to be found."
Justice Stephen Breyer wrote a separate dissent in which he said, "In my view, there simply is no untouchable constitutional right guaranteed by the Second Amendment to keep loaded handguns in the house in crime-ridden urban areas."
Joining Scalia were Chief Justice John Roberts and Justices Samuel Alito, Anthony Kennedy and Clarence Thomas. The other dissenters were Justices Ruth Bader Ginsburg and David Souter.
Gun rights supporters hailed the decision. "I consider this the opening salvo in a step-by-step process of providing relief for law-abiding Americans everywhere that have been deprived of this freedom," said Wayne LaPierre, executive vice president of the National Rifle Association.
The NRA will file lawsuitstrained. "We're pleased that the Supreme Court affirmed that the Second Amendment protects the right of Americans to keep and bear arms," White House spokesman Tony Fratto said.
Scalia said nothing in Thursday's ruling should "cast doubt on long-standing prohibitions on the possession of firearms by felons or the mentally ill, or laws forbidding the carrying of firearms in sensitive places such as schools and government buildings."
In a concluding paragraph to the his 64-page opinion, Scalia said the justices in the majority "are aware of the problem of handgun violence in this country" and believe the Constitution "leaves the District of Columbia a variety of tools for combating that problem, including some measures regulating handguns."
The law adopted by Washington's city council in 1976 bars residents from owning handguns unless they had one before the law took effect. Shotguns and rifles may be kept in homes, if they are registered, kept unloaded and either disassembled or equipped with trigger locks.
Opponents of the law have said it prevents residents from defending themselves. The Washington government says no one would be prosecuted for a gun law violation in cases of self-defense.
The last Supreme Court ruling on the topic came in 1939 in U.S. v. Miller, which involved a sawed-off shotgun. Constitutional scholars disagree over what that case means but agree it did not squarely answer the question of individual versus collective rights.
Forty-four state constitutions contain some form of gun rights, which are not affected by the court's consideration of Washington's restrictions.
The case is District of Columbia v. Heller, 07-290.
