The city is cracking down on people who post illegal signs, asking one advertiser to pay about $800 for the costs involved in removing such signs.
The person involved, whose identity was not disclosed by the city, has been posting illegal signs throughout the city advertising a "diet breakthrough."
More than 200 of the signs were placed on utility poles and other public rights of way, said Ted Porlas, code enforcement officer.
If the advertiser does not reimburse the city for its investigative and administrative costs, criminal misdemeanor charges will be filed, Porlas said.
"This is a commercial enterprise and this person is attempting to use the public rights of way for his own personal profit purposes," Porlas said.
Porlas found the suspected culprit by first calling the phone number on the signs, which rang at a voice-mail station at a Los Angeles answering service.
The company would not reveal the name of its customer, so the City Council last week approved subpoenaing the information.
Porlas warns others to think twice before tacking up a sign on a utility pole or public way in Fountain Valley.
The city may not only seek restitution but may pursue prosecution, he said.
"It's our policy to keep an aesthetically clean city--and we pride ourselves as such," Porlas said.