A federal appeals court has struck down a noise regulation for national parks, ruling that it violated protesters' First Amendment rights.

The case, decided Tuesday by the U.S. Court of Appeals, involved a violation of the 60-decibel noise limit set by the National Park Service. Park Police charged Diane Nomad, an opponent of the Persian Gulf War, with exceeding that noise level when she and others sang, chanted and beat on drums in Lafayette Square, across from the White House.

In ruling that the noise regulation was invalid, the unanimous three-judge panel said the Park Service's rule was not "narrowly tailored to serve a significant government interest."

Lafayette Square is a traditional setting for protests, the appeals court said. And because noise from passing traffic often exceeds the 60-decibel limit, the judges said the Park Service "by no reasonable measure . . . may lay claim to a legitimate interest in maintaining tranquility."