A panel of federal appellate judges questioned yesterday whether a ban preventing young adults from possessing cans of spray paint does indeed bolster the city’s anti-graffiti efforts.

A lower court barred the city from enforcing the law last month, but the city was allowed to continue enforcement pending further action by the courts.

The law forbids 18- to 20-year-olds from either purchasing or carrying cans of spray paint or broad-tipped markers on city property. The law came under fire in April when several artists sued the city, claiming that it hampered their ability to make their artwork.

The three-judge panel must decide whether to put into effect an order from a U.S. District Court Judge in Manhattan, George Daniels, that forbids the city from enforcing the law.

During brief oral arguments yesterday, the judges seemed skeptical of the city’s argument that the law served its intended purpose. Noting that a separate state law already forbids vandalizing property, Judge Jon Newman questioned the need for this additional law. Considering the possibility that Judge Daniels’s order would go into effect, he said: “It’s not as if the order unleashes all 19-year-old graffiti artists to spray paint on buildings.”

The panel had indicated it would issue a ruling by the end of the day yesterday. At 5 p.m. both a spokeswoman for the city’s law department and the lawyer representing the artists said that they had not received any order.

The law in question is rarely enforced. Since Mayor Bloomberg signed it at the end of last year, police have issued summonses to only two people between the ages of 18 and 21. During the same time period, the state law against vandalism has been invoked in 871 graffiti-related arrests, the lawyer for the plaintiffs, Daniel Perez, said.

As a city attorney, Virginia Waters, defended the usefulness of the law, the chief judge of the 2nd Circuit, John Walker, at one point mocked the city’s position by asking: “We are getting into graffiti season, aren’t we?”

Mr. Bloomberg has made anti-graffiti efforts an important element of his “quality of life” campaign over the last two years. Even so, New York’s anti-graffiti measures are less stringent than laws elsewhere in America. Chicago in the early 1990s banned the sale of spray paint to adults and minors, a fact that Ms.Waters cited in her remarks before the panel yesterday. Mr. Perez responded that the Chicago law, unlike the New York City law, was never challenged on First Amendment grounds.

The panel expressed some skepticism at the lawsuit’s claim that the young artists have faced harm under the ordinance.

Judge Newman asked whether any of Mr. Perez’s students had been unable to obtain spray paint or broadtipped markers since the ordinance went into effect. Mr. Perez acknowledged that his clients have been able to obtain art supplies through friends and that none of his clients have received a police summons under the law.

But Mr. Perez told the judges that the artists he represents fear arrest when they leave home with spray paint or broad-tipped markers. The plaintiffs include high school and college students as well as professional artists. All the artists use graffiti in their work but none of them vandalize private or city property, he said. The fashion designer Marc Ecko has backed the lawsuit.

When he issued his preliminary injunction against enforcement of the law in early May, Judge Daniels indicated that the law’s constitutionality will be judged, in part, by whether the City Council had a rational reason to pass the law. Ms.Waters has presented data suggesting that a full 20% of graffiti arrests are of people between the ages of 18 and 20.

Mr. Perez has suggested that the law was enacted without a great deal of research. Outside of court, he said he believes that the concerns of paint manufacturers and various retailers, who feared losing revenue from a general ban on spray paint, convinced the City Council to only limit the ban to a relatively small age group.

During yesterday’s hearings, Ms. Waters argued that the court should rule in the city’s favor because it is the city’s prerogative to make laws according to its judgment.

“We are asking that the court give the usual deference it gives to legislative enactments,” she said.