San Francisco may have gone too far in mandating warnings about the radiation coming out of cell phones, a federal judge ruled on Thursday.

The ruling, reported by the San Francisco Chronicle, called for San Francisco to tone down its message and to remove the requirement for retailers to post warnings on their walls.

U.S. District Judge William Alsup said the warnings created an "untrue and misleading" perception that cell phones are dangerous and "somehow escaped the regulatory process." He added that the rule overstates the risks posed by cell phones.

The ruling is part of an ongoing debate over the safety of cell phones and exactly how much radiation is emitted from the mobile devices. Phones sold in the U.S. must go through safety tests set by the Federal Communications Commission, which hasn't found dangerous levels of radiation.

It's a particularly sensitive issue for the wireless industry, as the trade group CTIA Wireless has proactively fought the San Francisco ordinance.

The ordinance was supposed to go into effect last week. It required retailers to hand out fact sheets carrying a World Health Organization classification that the phones' signals are a possible carcinogen. Retailers would also have to put the sheets up on their walls.

The ruling doesn't bar the fact sheets from being distributed, but it requires San Francisco to adjust them so the implications of radiation threat aren't so direct.

City Attorney Dennis Herrera said he would appeal the ruling, the Chronicle reported.