At issue is the city's law forcing cell phone retailers to warn customers about potential health risks. It's on hold while the two sides fight it out.
San Francisco passed what's called the "Right to Know" law two years ago, making it the only city in the nation to require customer warnings for cell phones. But the industry has sued, saying the groundbreaking measure violates retailers' First Amendment rights by forcing them to provide messages they oppose.
Andrew McBride, an attorney for the cell phone industry said at the hearing: "The FDA and the FCC have said the phones are safe. They are as safe as we can make them under federal safety standards."
But San Francisco points out that the World Health Organization has classified radio-frequency energy from cell phones as being possibly cancer causing.
"There is no rule that says that the government must wait until we know that a product actually kills people -- that we have conclusive proof," San Francisco Deputy City Attorney Vincent Chhabria said.
The city's measure calls for customers to be given a notice about radio-frequency energy that includes recommendations such as limiting cell phone use by children, using a headset or speaker phone and reducing the number and length of calls.
Public opinion is mixed. "It's like a warning label. They put it on cigarettes. They put it on other items, so why not cell phone usage?" said Marijke Adams.
When shown an example of the notice, Tony Theophilos said: "I think this is absolutely ridiculous, and it's just like all the other notices that are posted in retail establishments. Nobody reads them anyway."
Thursday's hearing before the appellate judges came after a lower court ruling led San Francisco to scale back some of its warning language. The city wants it reinstated. The industry wants the entire law overturned.
There's no timetable for the Court of Appeals to rule, and in the meantime, San Francisco's cell phone law remains on hold.