Angela Lang/CNET

Wireless association CTIA has failed again to get the city of Berkeley, California, to stop warning people that using a cellphone could expose them to radiation. As part of the long-running debate over health concerns in using mobile phones, Berkeley's "Right to Know" ordinance, which came into effect in 2016, was upheld by a court Tuesday.

Berkeley had been enforcing a city ordinance that required phone retailers to inform prospective buyers that carrying phones in certain ways, like in pants pockets or bras, could cause them to exceed the FCC's guidelines for radio frequency radiation maximum exposure. CTIA had argued that this violated the First Amendment, blocking retailers' freedom of speech by requiring them to post "inflammatory" messages.

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The radiation warning message required by the city from phone retailers is: "To assure safety, the Federal Government requires that cell phones meet radio frequency (RF) exposure guidelines. If you carry or use your phone in a pants or shirt pocket or tucked into a bra when the phone is ON and connected to a wireless network, you may exceed the federal guidelines for exposure to RF radiation. Refer to the instructions in your phone or user manual for information about how to use your phone safely."

CTIA sued in June 2015, trying to stop Berkeley through an injunction. In April 2017, the 9th US Circuit Court of Appeals upheld the ordinance, finding it was in the public interest and based on FCC information. But in June 2018, the Supreme Court returned the case to the lower court for further review.

After the Supreme Court decision, CTIA said it would continue its fight against "forcing retailers to convey the government's message." At the same time, Matthai K. Chakko, Berkeley's communications director, said the city didn't think the decision would affect the ordinance.

In 2013, after a three-year battle, the CTIA prevented San Francisco from requiring phone radiation messages.

Farimah Faiz Brown, Berkeley's city attorney, said the city is pleased with the court's ruling.

"The city has always firmly believed that the ordinance is constitutional and serves the public interest," she said in an emailed statement Tuesday afternoon.

The CTIA said in a statement that it is disappointed that Berkeley is continuing "to mislead the public" about mobile networks being harmful.

"Radiofrequency energy from wireless devices and networks, including 5G, has not been shown to cause health problems, according to the consensus of the international scientific community," the CTIA said in an emailed statement Wednesday morning.

The group has a 90-day window to consider its legal options.

First published July 2 at 3:05 p.m. PT.

Update at 3:54 p.m. PT: Adds comment from Berkeley city attorney

Update July 3 at 12:58 p.m. PT: Adds comment from the CTIA