SAN FRANCISCO — Retailers selling mobile phones will continue to have to warn customers in the City of Berkeley about possible exposure to radiation from the devices, after a federal appeals court on Wednesday declined to revisit a ruling upholding the city's rule.

The U.S. Court of Appeals for the Ninth Circuit denied a petition for rehearing and for en banc review of a panel's April decision allowing Berkeley's cell phone ordinance to stay in place. The court adhered to the panel's view that the ordinance compels purely factual speech, and is related to a “substantial government interest.”

Accordingly, it concluded that CTIA, a wireless industry trade association that sued to block the ordinance, “had little likelihood of success on its First Amendment claim that the disclosure compelled by the Berkeley ordinance was unconstitutional.”

“The decision of the district court was correct — twice. The decision of the court of appeals was correct — now twice,” Harvard Law professor Lawrence Lessig, who argued for the city in the case, said in an email. “We are hopeful that this will bring an end to this case, and the City of Berkeley will again be free to govern its citizens as its citizens demand.”

CTIA was represented in the case by Theodore Olson of Gibson, Dunn & Crutcher. Jilane Petrie, a spokeswoman for the group, said in a statement: “The courts have acknowledged that Berkeley has presented no evidence that cell phones cause harmful effects.  We will continue to assert that the First Amendment prohibits the government from forcing private companies to promote misleading and inaccurate opinions.”

The First Amendment issue split the original panel. In a dissent, Ninth Circuit Judge Michelle Friedland wrote that her colleagues' approach of reading Berkeley's ordinance line-by-line to analyze it for factual accuracy “misses the forest for the trees.”

“Taken as a whole, the most natural reading of the disclosure warns that carrying a cellphone in one's pocket is unsafe,” Friedland wrote. “Yet Berkeley has not attempted to argue, let alone to prove, that message is true.”

On Wednesday, Circuit Judge Kim Wardlaw also dissented from the denial of rehearing and en banc review — albeit for different reasons — saying she would grant both.

“Ordinarily, I do not file 'dissentals,' particularly where there is an existing dissent,” Wardlaw wrote. “I am compelled to write here, however, because Judge Friedland's dissent, which I agree with entirely, rests principally on the ground that the required disclosure is itself misleading, whereas I believe the panel majority applied the wrong legal standard.”

Wardlaw argued the panel had applied a lenient standard of scrutinizing compelled speech — known as the Zauderer standard — that should only be used when the measure at issue aims to prevent consumer deception.

“The government is not allowed to compel disclosures to shape consumer behavior to its own design,” she wrote, “particularly when governments have other powerful means, such as taxation, market regulation, and education efforts, to advance their interests.”