A federal appeals court in Washington yesterday let stand a ruling that struck down a restrictive D.C. ban on gun ownership, setting the stage for a potentially major constitutional battle over the Second Amendment in the Supreme Court.

D.C. Mayor Adrian M. Fenty said at a news conference that he was "deeply disappointed" by the court's decision not to reconsider the city's arguments that the three-decades-old gun ban was constitutional. Fenty (D) said the city will now mull over whether to take the risk of pressing to defend the D.C. gun law before the Supreme Court or to rewrite gun regulations for keeping guns in private District homes.

"As mayor, I remain committed to combating gun violence, and . . . this is a critical part of the District's crime-control strategy," he said. "The predominant factor in our consideration [of how to proceed] will be the safety of District residents."

Fenty and other officials had asked the full appeals court to review a ruling issued by a three-judge panel that struck down a part of the D.C. law that bars people from keeping handguns in homes. With its 6 to 4 vote to reject a hearing by the full court, the U.S. Court of Appeals for the D.C. Circuit sped up the timetable for a showdown. Experts said that timetable favors gun rights advocates and the D.C. residents who first challenged the law.

"Clearly it would have been better for us to have another chance to argue before the full court," said D.C. Attorney General Linda Singer. "It goes much faster now."

If the city petitions for a hearing before the Supreme Court -- and it must make that decision within 90 days -- legal experts say the high court probably will agree to take the case within a year.

A central question the D.C. case poses is whether the Second Amendment protects an individual's rights to bear arms. In its 2 to 1 ruling in March, the appellate panel ruled that it does.

The Bush administration is on record supporting the argument that the Second Amendment protects individual rights, and it would be able to argue that view if the case is heard soon. If the full appeals court had heard the case, a new administration might have taken a different stance by the time it reached the Supreme Court.

"That's very important to have the government on our side," said Robert A. Levy, a libertarian lawyer who spearheaded the challenge to the law. "And that could change with a new administration."

Experts say that gun-rights advocates have never had a better chance for a major Second Amendment victory, because a significant number of justices on the Supreme Court have indicated a preference for the individual-rights interpretation.

Another appellate court that considered a similar case, in the 5th Circuit, chose not to strike down a gun law based on that individual-rights interpretation. Other appellate circuits have interpreted the amendment as protecting a militia's right to take up arms -- not an individual's. The question is whether the Supreme Court considers that a substantial enough legal conflict demanding the court's resolution.

Paul Helmke of the pro-gun-control Brady Center to Prevent Gun Violence said he believes the Supreme Court will want to settle the matter. "We've expected all along this would go the Supreme Court," Helmke said. "The crucial thing is, it gets it there quicker. If the court takes the case, there's a chance there'll be a ruling just before the presidential election. That will make it politically interesting."

D.C. Assistant Police Chief Winston Robinson Jr. said he's sorry that some residents don't feel safe in their homes without guns but stressed that the recent massacre at Virginia Tech should remind them that guns don't increase safety.

"More than likely, that weapon in their home will be used against them," Robinson said. "Just think about what happened recently in Virginia: guns in the hands of people who shouldn't have them."

Those voting against a new hearing were one judge who joined in the original opinion, Thomas B. Griffith, and one who dissented from it, Karen LeCraft Henderson, as well as Chief Judge Douglas H. Ginsburg, David B. Sentelle, Janice Rogers Brown and Brett M. Kavanaugh. Those voting to reconsider were Merrick B. Garland, Judith W. Rogers, David S. Tatel and A. Raymond Randolph.