Americans have an individual right to possess and use firearms, even when the guns are not related to service in a government militia.

In a historic ruling, the US Supreme Court on Thursday declared 5 to 4 that the Second Amendment's guarantee of a right to "keep and bear arms" means that the government cannot enact an outright ban on certain commonly held weapons or otherwise prevent citizens from having a gun at home for personal protection or other lawful uses.

The landmark constitutional pronouncement came as the nation's highest court struck down a 32-year ban on private possession of handguns in Washington, D.C. The court also invalidated two other strict gun-control measures in the district that required that rifles and shotguns at all times be kept disassembled or secured with a trigger lock. The case is District of Columbia v. Heller.

"We hold that the District's ban on handgun possession in the home violates the Second Amendment, as does its prohibition against rendering any lawful firearm in the home operable for the purpose of immediate self-defense," Justice Antonin Scalia wrote in the majority opinion.

The majority justices said the District's strict gun regulations violated "the right of law-abiding responsible citizens to use arms in defense of hearth and home."

Justice Scalia's majority opinion was joined by Chief Justice John Roberts and Justices Anthony Kennedy, Clarence Thomas, and Samuel Alito.

In a dissent, Justice Stephen Breyer said the case would spawn unfortunate consequences. "The decision threatens to throw into doubt the constitutionality of gun laws throughout the United States," Justice Breyer wrote. "I can find no sound legal basis for launching the courts on so formidable and potentially dangerous a mission."

Scalia and the majority justices declined to spell out precisely the legal standard future courts should use in weighing whether someone's Second Amendment right had been infringed. But they left no doubt that it is a robust one.

"Under any standards of scrutiny that we have applied to enumerated constitutional rights, banning from the home the most preferred firearm in the nation to keep and use for protection of one's home and family, would fail constitutional muster," Scalia wrote.

While the high court struck down the Washington, D.C., regulations, it remains unclear how many other gun-control measures may now be on shaky constitutional ground. Some analysts suggest that a handgun ban in Chicago, similar to the ban in Washington, may emerge as the next constitutional battleground over gun rights.

Scalia sought to address concerns by many critics – and the dissenting justices – that such a ruling might lead to an arms race among American homeowners stocking up with machine guns, grenades, and rocket launchers.

"The right secured by the Second Amendment is not unlimited," Scalia wrote. "Nothing in our opinion should be taken to cast doubt on longstanding prohibitions on the possession of firearms by felons and the mentally ill," he said. The opinion did not undermine laws "forbidding the carrying of firearms in sensitive places such as schools and government buildings," he said.

He added that the opinion did not undercut laws imposing conditions and qualifications on the commercial sale of arms.