BERKELEY, Calif. (AP) — A federal judge has allowed Berkeley to start requiring cell phone retailers to warn customers about possible radiation risks.

The San Francisco Chronicle reports that U.S. District Judge Edward Chen of San Francisco says the city can require retailers to say carrying switched-on phones too close to a person’s body might violate federal radiation standards.

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Chen blocked Berkeley from making such notifications in September, when CTIA-The Wireless Association filed a lawsuit arguing the rule violated freedom of speech.

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But Chen ruled Wednesday the warnings can be enforced now that Berkeley removed a disputed claim that the potential risk is greater for children.

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CTIA is asking a federal appeals court to declare Berkeley’s rule unconstitutional.