San Francisco and the CTIA are at odds yet again now that the wireless association has formally challenged cell phone warning legislation that the city passed earlier this year.

In a statement released Tuesday, John Walls, the CTIA's vice president of public affairs, called San Francisco's actions "both alarmist and false" and disputed any suggestion that the radio frequency (RF) emissions produced by cell phones have detrimental health effects. "The FCC and FDA have repeatedly found that cell phone use does not pose a danger," he said. "The Ordinance recommends such things as turning the phone off when not in use, a suggestion that would render critical emergency communications unavailable to San Francisco residents."

The "Right to Know" ordinance (PDF), which the 11-member San Francisco Board of Supervisors approved unanimously on July 19, requires San Francisco retailers to post informational posters (PDF) that cell phones emit RF energy and offer fact sheets to consumers who request them. In addition to stating that the World Health Organization has classified RF energy as a possible carcinogen, the fact sheets (PDF) suggest that consumers can reduce RF exposure by limiting phone use, wearing a belt clip, and using a headset.

According to court documents (PDF), the CTIA is alleging that the city's ordinance violates the First Amendment rights of retailers and that it conflicts with the Federal Communications Commission's oversight of wireless safety standards. "The federal government has exclusive jurisdiction to regulate the safety of the RF emissions from cell phones," the CTIA's suit says.

City Attorney Dennis Herrera quickly fired back at the CTIA's complaint (PDF) by saying the trade group is "keeping people in the dark" about a legitimate health concern. "I'm disappointed that the wireless industry is so bent on quashing the debate about the health effects of cell phone radiation," Herrera said in a statement. "And I'm especially troubled that the industry is invoking the First Amendment."

If the spat sounds familiar, it's because it is. The new ordinance actually is a revised version of broader legislation that the previous board passed in June 2010. As originally written (PDF), that bill would also have required retailers in the city to post the specific absorption rate (SAR) of each phone sold.

Though the SAR labeling provision won praise from environmental health groups, it also angered the CTIA, which sued San Francisco on similar grounds. After delaying implementation for months, city officials finally agreed in May to shelve the original law and instead passed the watered-down language.

Herrera's office was set to respond to the CTIA's preliminary injunction today. Next, a hearing will take place in San Francisco before United States District Judge William Alsup on Thursday, October 20.