When is an illegal billboard not illegal? When it's in Miami. That's the frustrated cry of civic watchdogs as well as some Miami-Dade County officials who complain that the city is refusing to enforce laws limiting the spread of billboards, murals and other illegal advertising displays.

"The landscape is absolutely disgusting," says Nancy Liebman, president of the Urban Environment League, which has lobbied for tougher laws regulating outdoor signs in Miami-Dade. "We need to take pride in how the city looks." At issue are 400 or so billboards, many of which run afoul of both city permitting requirements and a 20-year-old county ordinance limiting their content and placement.

Last year, after being pressed by the Urban Environment League and other local groups, the county commission passed a resolution requiring the city to take action. But few signs in Miami have been removed. Some billboard owners are paying fines in exchange for agreements allowing their signs to remain. And earlier this year, city officials considered an ordinance legalizing the city's unauthorized billboards. The measure was tabled after opponents noted it would be in violation of the county's ordinance.

Miami-Dade County Commissioner Katy Sorensen, who sponsored the resolution and who continues to press the issue despite indifference from commission colleagues, remains miffed at the city's stance. She's also frustrated that county administrators are failing to enforce their own laws, relying instead on municipalities to monitor compliance.

The problem goes beyond billboards. In recent months, Miami has fanned the outdoor advertising fire by permitting dozens of wall murals -- advertising such products as iPod and Bud Light -- throughout downtown. City officials sidestep local billboard laws by calling the signs "art," charging up to $10,000 each in licensing fees.

Such revenue is not the city's motivation, argues Liebman. She accuses city officials of refusing to stand in the way of the powerful outdoor advertising lobby, which routinely opposes local and state restrictions. Outdoor advertising is big business: Choice billboard locations in Miami can command more than $200,000 per year. Building owners collect similar fees for renting wall space for murals.

"People need to realize that this affects their quality of life," says Liebman, noting that Miami's new $412-million Performing Arts Complex is partly obscured by a billboard. "This is a virtual blight on our community, and our public officials have to start paying attention."