The mobile industry is trying to shoot down another law requiring cellphone radiation warnings.

CTIA sued the city of Berkeley, California, on Monday, taking aim at a law passed in May that would force cellphone retailers to post a notice about safety from radiofrequency radiation emitted by handsets. CTIA, the main trade group for U.S. mobile operators, says the law will force its members to pass on an inaccurate message that they don’t agree with.

Just a few years ago, CTIA successfully fought a similar law in nearby San Francisco. That law required phone sellers to disclose the emissions produced by each model. The disputes are part of a smoldering debate over whether phones and other wireless devices give off radiation that may be harmful to humans. CTIA, and the Federal Communications Commission, say there is no evidence of a health risk from approved devices.

Berkeley’s warning message says carrying a phone in a pocket or tucked into a bra could expose users to radiation above federal guidelines. “The potential risk is greater for children,” the warning says. It advises consumers to read the instructions included with their phone for information about how to use it safely.

The law uses the fact that radiation tests for phones aren’t conducted with the handset right next to the body, even though many people carry them that way. CTIA says that’s misleading because FCC-approved tests are done at levels well above what users are normally exposed to and there’s no evidence of a risk even when radiation levels exceed the FCC limits. There’s no evidence that children are at greater risk, either, it says.

“In short, when a cell phone is certified as compliant with the FCC’s guidelines, that phone is safe, however it is worn, even if a particular usage results in exposure ‘well above’ the limit,” CTIA said in its complaint.

The suit, filed in the U.S. District Court for Northern California, came soon after the Berkeley City Council unanimously passed the law on May 26. The law is due to take effect after 30 days.

Berkeley’s law violates phone retailers’ freedom of speech under the First Amendment, the complaint said. If allowed to stand, it will lead other local governments to follow Berkeley’s lead, creating a mishmash of different laws about what retailers have to tell consumers, CTIA said.

The City of Berkeley declined to comment on pending litigation.