The U.S. Supreme Court ruled Thursday that individuals have a right to own a handgun and use it for personal defense in their home, overturning a law prohibiting private citizens from possessing handguns in the District of Columbia.

The 5-4 decision, written by Justice Antonin Scalia, marked the first time the court has ruled on any aspect of the Second Amendment since 1939, and the first time it ever has addressed the meaning of the amendment’s 27 words.

Mayor Adrian Fenty called the decision unfortunate and disappointing, saying that “the same way illegal guns move through the black market, legal guns will move through the black market and end up in the hands of criminals.”

Reaction from Congress was swift. House Judiciary ranking member Lamar Smith (R-Texas) released a statement applauding the ruling.

“This is a resounding victory for the American people and sets a strong precedent that the rights and liberties provided in the Constitution may be regulated but cannot be extinguished by the law,” he said.

Scalia was joined in the majority by Chief Justice John Roberts and Justices Anthony Kennedy, Clarence Thomas and Samuel Alito.

But he stressed that the decision was not absolute, which presumably means that the District could, for example, maintain its ban on handguns outside the home.

“Like most rights,” Scalia wrote, “the Second Amendment right is not unlimited. It is not a right to keep and carry any weapon whatsoever in any manner whatsoever and for whatever purpose.”

There were two dissenting opinions, one by Justice John Paul Stevens and one by Justice Stephen Breyer. Both dissents were joined by Justices Ruth Bader Ginsburg and David Souter.

Scalia also emphasized that the decision would not impact certain specific and narrowly tailored restrictions on firearms ownership.

“The court’s opinion,” he wrote, “should not 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.”

The ruling in District of Columbia v. Heller overturned two provisions of the D.C. law: one forbidding private citizens from owning guns and another that required any gun, with the exception of those kept at a business, to be disassembled and unloaded or kept with a trigger lock.

The handgun ban has been in place in the District since 1976, less than two years after it was granted home rule by Congress. The court battle to determine its constitutionality began in 2003.

Fenty emphasized that handguns will remain illegal in the District for the next 21 days as the police department devises a plan of action for dealing with the new law. The city plans to eventually have an amnesty period during which people who illegally own guns can register them without a penalty.

The Second Amendment, in its entirety, 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.”

Until now, the Supreme Court had never ruled on whether that single sentence protected an individual’s right to own a firearm, “unconnected with service in a militia,” as Scalia explained in his opinion, or “that it protects only the right to possess and carry a firearm in connection with military service.”

Scalia’s interpretation, strongly rejected by the dissenters, is that it is an individual right. “The term was applied, then as now, to weapons that were not specifically designed for military use and were not employed in a military capacity,” he wrote.

The Brady Campaign to Prevent Gun Violence, a nonpartisan grass-roots organization that aims to prevent gun violence, said the decision upends the argument of pro-gun supporters that modest gun control measures inevitably will lead to a total ban on gun ownership.

“For years, the gun lobby has used fear of government gun confiscation to thwart efforts to pass sensible gun laws, arguing that even modest gun laws will lead down the path to a complete ban on gun ownership,” the Brady Center’s Paul Helmke said in a statement. “Now that the Court has struck down the District’s ban on handguns, while making it clear that the Constitution allows for reasonable restrictions on access to dangerous weapons, this ‘slippery slope’ argument is gone.”