WASHINGTON -- The 2nd Amendment right to "keep and bear arms" finally had its day in the Supreme Court on Tuesday, and the long-held view that it protected the rights of gun owners appeared poised to win a historic victory.

Five of the justices, a bare majority, signaled that they thought the amendment gave individuals a right to have a gun for self-defense. It was not limited to arms for "a well-regulated militia," they said.

By adopting that view, the justices are likely to strike down the nation's strictest gun control law, a ban on handguns in the District of Columbia.

But Chief Justice John G. Roberts Jr. said he favored a narrow ruling, one that would not cast doubt on an array of gun control laws across the nation. They include a ban on the sale of new machine guns, required background checks for new buyers of handguns and state licensing rules for those who wish to carry a concealed weapon.

"But I don't know why when we are starting afresh we would try to articulate a whole standard that would apply in every case." Roberts told one lawyer.

The court is indeed "starting afresh" with the 2nd Amendment, more than 200 years after it was adopted as part of the Bill of Rights. It says: "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 high court has never struck down a gun control law for violating the 2nd Amendment.

For many years, judges thought the amendment merely prohibited the federal government from interfering with the state's right to maintain a "well-regulated militia."

But most Americans know the second clause, referring to the "right of the people to keep and bear arms." In polls, a large majority say they think it gives law-abiding people a right to own a gun.

Though the court appeared ready to agree with them, the chief justice alluded to the difficulty of deciding what kind of right was protected by the 2nd Amendment. Is the right to own a gun like the right to freedom of speech in the 1st Amendment? If so, most restrictions on that right would be in doubt. Or is the gun right subject to strict regulations by the government?

The justices strongly hinted Tuesday that they would leave open the question of whether many restrictions on gun rights would stand.

Nonetheless, a ruling recognizing an individual right in the 2nd Amendment would be a landmark. And it could well signal the beginning of an era in which anti-gun regulations are subject to legal challenges.

The case heard by the court Tuesday began when Robert A. Levy, a libertarian lawyer at the Cato Institute who lives in Florida, decided to challenge the District of Columbia's 30-year-old ban on handguns. One plaintiff, Dick A. Heller, is a private security guard who wants to keep his handgun at home.

Last year, the U.S. appeals court here struck down the law, prompting the city to appeal the case of District of Columbia vs. Heller.

Washington lawyer Walter Dellinger, defending the city's law, began by arguing the Constitution's framers sought to protect state militias. The phrase "bear arms" refers to the "military context," he said.

But he ran into skeptical questioning.

Justice Anthony M. Kennedy made clear he thought the 2nd Amendment included an individual right to self-defense. "In my view . . . there's a general right to bear arms quite without reference to the militia," he said.

"If it is limited to state militias, why would they say 'the right of the people?' " Roberts asked.

Justice Antonin Scalia pointed out that "Blackstone thought the right to self-defense was inherent," and early members of the Supreme Court saw the 2nd Amendment "as a personal guarantee" of the right to self-defense.

Switching gears, Dellinger argued that the District of Columbia law was a reasonable regulation of gun ownership.