The law, as passed, also applied to advertising banners trailed by airplanes and ads on blimps. But in the first of what promises to be a long series of legal challenges, a court ruled the clause unconstitutional on the grounds that the federal government, not the city, controls airspace.

"What we are aiming for is a complete change of culture," said Roberto Tripoli, president of the City Council and one of the main sponsors of the legislation. "Yes, some people are going to have to pay a price. But things were out of hand and the population has made it clear it wants this."

The law, approved by a vote of 45 to 1 in September, goes into effect on Jan. 1. Opponents complain that the date does not allow enough time for merchants to comply, that fines of up to $4,500 for violations are extreme and that the result will inevitably be a diminishing of urban life — "like New York without Times Square or Tokyo without the Ginza," Solimeo said.

"I think this city is going to become a sadder, duller place," said Dalton Silvano, who cast the sole dissenting vote and is in the advertising business. "Advertising is both an art form and, when you're in your car or alone on foot, a form of entertainment that helps relieve solitude and boredom."

This is not the city's first effort to regulate outdoor advertising. A few years ago it was prohibited in the historic downtown area. But there have been complaints about inspectors taking bribes and advertisers simply flouting the law.

"All our efforts to negotiate have had no effect because none of the accords and agreements we reached with the advertising sector were ever complied with," Mayor Gilberto Kassab said in an interview. "A billboard that was forced to come down would be back up a week later in a different spot. There was a climate of impunity."

Since "it is hard in a city of 11 million to find enough equipment and personnel to determine what was and wasn't legal, we decided to go all the way, to zero things out," Kassab said. "When you prohibit everything, society itself becomes your partner in enforcing the law" and reporting violations.