The court's 5-4 ruling struck down the District of Columbia's 32-year-old ban on handguns as incompatible with gun rights under the Second Amendment. The decision went further than even the Bush administration wanted, but probably leaves most firearms laws intact.
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.
"Gun rights advocates now have a fully recognized individual right to bear arms. But gun control advocates now have a Supreme Court ruling that declares that this right, like other rights in the Constitution, is not absolute. So we finally get some clarity in an area of the law that was begging for it," writes CBS News chief legal analyst Andrew Cohen.
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.
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.
Cohen cautions that the ruling will not "immediately end all gun control regulation around the country. Jurisdictions that want to control guns - especially outside the home - still will be able to do so in some fashion."
The NRA will file lawsuits in San Francisco, Chicago and several of its suburbs challenging handgun restrictions there based on Thursday's outcome.
Sen. Dianne Feinstein, D-Calif., a leading gun control advocate in Congress, criticized the ruling. "I believe the people of this great country will be less safe because of it," she said.
The capital's gun law was among the nation's strictest.
Dick Anthony Heller, 66, an armed security guard, sued the District after it rejected his application to keep a handgun at his home for protection in the same Capitol Hill neighborhood as the court.
The U.S. Court of Appeals for the District of Columbia ruled in Heller's favor and struck down Washington's handgun ban, saying the Constitution guarantees Americans the right to own guns and that a total prohibition on handguns is not compatible with that right.
The issue caused a split within the Bush administration. Vice President Dick Cheney supported the appeals court ruling, but others in the administration feared it could lead to the undoing of other gun regulations, including a federal law restricting sales of machine guns. Other laws keep felons from buying guns and provide for an instant background check.
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.