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.”