WASHINGTON - Their shtick is safe. A federal appeals court Friday freed tour guides in the nation's capital from having to prove they know what they're talking about.

The court struck down licensing regulations that required the city's ubiquitous guides to pass a 100-question exam testing their knowledge of the city's attractions and history. The regulations were challenged by Tonia Edwards and Bill Main, who lead tourists on rented Segway scooters to Washington's historic sights.

In defending the licensing, the city argued that guides should be certified as having at least a minimal grasp of the city's history and geography.

But in a 3-0 decision on a free speech issue, the U.S. Court of Appeals for the District of Columbia Circuit said the city failed to present any evidence the problems it sought to thwart actually exist.

Operating as a paid tour guide in Washington without a license has been punishable by as many as 90 days in jail and a $300 fine.

And the court said that even if the harms are real, there is no evidence the city's exam requirement is an appropriate antidote.

"The city has provided no convincing explanation as to why a more finely tailored regulatory scheme would not work," Judge Janice Rogers Brown wrote for the appeals court.

Brown suggested one approach might be a voluntary certification program, with guides who take and pass the preferred exam can advertise as city-certified guides.

The city requires a $200 payment for tour guides, but Main told a news conference "it's not about the money. The money is not prohibitive."

Main said his business hires a number of college students on summer vacation who lose work time because they have to spend time on the exam.

The appeals judges noted that the multiple-choice questions fall into 14 categories: architecture; dates; government; historical events; landmark buildings; locations; monuments and memorials; museums and art galleries; parks, gardens, zoos and aquariums; presidents; sculptures and statues; universities; pictures and regulations.

Earlier, a federal judge had said the requirement placed only incidental burdens on speech that were no greater than necessary to further the District of Columbia's substantial interest in promoting the tourism industry.

The appeals court reversed, saying it found the record devoid of evidence supporting the burdens the challenged regulations impose.

The appeals court panel said the city "rehearses a plethora of harms it claims to forestall with the exam requirement" - including unscrupulous businesses, visitors vulnerable to unethical or uninformed guides, tourists treated unfairly or unsafely, tourists who are swindled or harassed, tour guides abandoning tourists in some far-flung spot or charging them additional amounts to take them back.

The panel said that despite the city's "seemingly talismanic reliance on these asserted problems," the record contains no evidence that ill-informed guides are actually a problem for the city's tourism industry.

"The First Amendment protects everyone who talks for a living, whether you're a journalist, a professor or a tour guide," Robert McNamara, an attorney in the case, said after Friday's ruling.

The appeals court in Washington took note of a contrary decision by the U.S. Circuit Court of Appeals for the 5th Circuit, which affirmed the constitutionality of a similar tour guide licensing procedure in New Orleans. McNamara said reconsideration of that decision is being sought.