The D.C. Court of Appeals yesterday warned motorists attempting to avoid police radar in the city that they better "leave their 'Fuzzbusters' behind."

A three-judge panel unanimously upheld the constitutionality of the city's ban on the radar detection devices, reminding travelers that just carrying one inside a car unused is unlawful.

"Radar detectors have no utility other than aiding an illicit effort to drive in an irresponsible manner, evading society's punishment for such conduct," wrote Judge Frank Q. Nebeker.

Besides the District of Columbia, only two states -- Virginia and Michigan -- prohibit the use of police radar detectors, according to a spokesman for Electrolert, one of several manufacturers of the devices. The devices are popularly called "Fuzzbusters," the trade name Electrolert adopted for them. The Electrolert spokesman estimated that more than 2 million Fuzzbusters are in use on the nation's highways.

The District law that prohibits possession as well as use of the device in a vehicle is the first to be upheld by an appellate court, according to Electrolert..

"It's a lovely victory," said Asst. Corporation Counsel Philip T. Van Zile. D.C. police officials said that each year they seize 50 to 60 of the devices, which are several inches long and range in price from $99 to $300.

"We feel they are not illegal," said Janice Lee, of Electrolert, in Troy, Ohio. "They work on the same principal as an AM-FM radio. They just receive radio waves. Everyone has the right to receive radio waves."

"We hardly get any reverberations from D.C.," where the fine for violating the radar detector law is $50, Lee said. "I'm sure now that this decision has come down, we're going to get a little flak."

Mark H. Kaufman, who represented the six motorists involved in the appeals case, said, "None of the individuals were really concerned about being fined $50. They felt the statute was unconstitutional and an infringement of their rights. I thought we had a good chance of winning."

Kaufman contended that in prohibiting the mere possession of the devices, the D.C. law was unconstitutionally broad. He also argued that only the U.S. government, through the Federal Communications Commission, should be able to regulate the devices.

Nebeker noted, however, that while a radar detector is indeed a radio receiver, its purpose is to avoid police and that it does not receive the kind of "communication" localities cannot regulate.

Nebeker's opinion, which upheld a D.C. Superior Court decision by Judge James A. Washington, Jr., was joined by Judges John W. Kern III and George R. Gallagher.