But in striking down a handgun ban in Washington, D.C. – a crime-plagued city with the nation’s toughest gun control laws – the court started a new debate over how far government can go to protect the public. Some regulations on possession and transfer of guns are “reasonable,” the court said in a 5-4 decision.

“Hallelujah. Praise the Lord and pass the ammunition,” said David Schenck, a Dallas lawyer who filed a brief on behalf of the Texas State Rifle Association and sister groups in 42 other states.

The question for courts, city councils and legislatures to sort out in coming years will be: Which restrictions pass muster? Gun rights advocates will be in court as early as today challenging handgun bans in Chicago and San Francisco’s public housing, and were looking for other ordinances to attack.

“I expect there will be a significant number of California laws challenged because there have been a significant number of irrational and counterproductive laws passed in the state in recent years,” said Chuck Michel, an attorney for the National Rifle Association and other gun groups.

Only hours after the ruling, two groups sued the City of Chicago over its handgun ban, which is similar to the Washington, D.C., law that the high court struck down. The NRA said it would file another lawsuit against Chicago today and also sue surrounding cities that ban handguns.

Gun control supporters said they would fight the challenges.

Chief Justice John Roberts issued the ruling on the final day of the court’s annual term. This was the first time the court had explicitly said the Second Amendment protects an individual right to gun ownership, and was its first hard look at gun rights since 1939.

“Like most rights, 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,” wrote Justice Antonin Scalia for the majority.

In a dissenting opinion, Justice John Paul Stevens took vigorous issue with Scalia’s assertion that it was the Second Amendment that had enshrined the individual right to own a gun. Rather, it was “today’s law-changing decision” that bestowed the right, Stevens said in a dissent joined by Justices David Souter, Ruth Bader Ginsburg and Stephen Breyer. Breyer, also speaking for the others, filed a separate dissenting opinion.

Scalia and Stevens went head- to-head in debating how the 27 words in the amendment should be interpreted. The majority opinion and the two dissenting opinions totaled 154 pages.

Stevens said the majority opinion was based on “a strained and unpersuasive reading” of the text and history of the amendment, which provides: “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.”

According to Scalia, the “militia” reference simply “announces the purpose for which the right was codified: to prevent elimination of the militia.” The Constitution’s framers were afraid that the new federal government would disarm the populace, as the British had tried to do, Scalia said.

But he added that this “prefatory statement of purpose” should not be interpreted to limit the meaning of what is called the operative clause – “the right of the people to keep and bear arms, shall not be infringed.” Instead, Scalia said, the operative clause “codified a pre-existing right” of individual gun ownership for private use.

Contesting that analysis, Stevens said the Second Amendment’s structure was notable for its “omission of any statement of purpose related to the right to use firearms for hunting or personal self-defense,” in contrast to the contemporaneous “Declarations of Rights” in Pennsylvania and Vermont that did explicitly protect those uses.

Scalia’s opinion was signed by Roberts, Anthony Kennedy, Clarence Thomas and Samuel Alito.

The case was filed by Dick Heller, a security guard at the Federal Judicial Center who was refused permission to keep his handgun at his D.C. home.

Scalia’s opinion contained significant qualifications.

“Nothing in our opinion,” Scalia said, “should be taken to cast doubt on long-standing 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.”

Both major party presidential candidates expressed support for the decision.

Republican Sen. John McCain called the decision “a landmark victory for Second Amendment freedom in the United States.”

Democrat Sen. Barack Obama praised the decision both for its endorsement of the individual-rights view and for its description of the right as “not absolute and subject to reasonable regulations enacted by local communities to keep their streets safe.”

The New York Times and the Los Angeles Times contributed to this report.