SAN FRANCISCO — From banning plastic shopping bags to making homeowners recycle their banana peels and coffee grounds, San Francisco has often led the way in writing the most cutting-edge or over-the-top laws in the land.

Now the city’s going after killer cell phones.

By making San Francisco the first place in America to require retailers to post radiation-emission information beside every make and model of phone they sell, city supervisors have once again dropped down a rabbit hole of controversial public policy. The cell phone lobby has come out with guns blazing, asking a judge to throw out the statute even though it doesn’t take effect for months. Public health advocates are going gaga over the ordinance, even while some scientists question its very premise.

“There are some studies that indicate increased rates of cancer from long-term use of cell phones, and others that don’t,” said Mark Westlund, spokesman for the city’s Department of the Environment, which is spearheading the ordinance first proposed by Mayor Gavin Newsom and passed by the board of supervisors in June. “So we took a precautionary approach.”

Prompted by a recent international study that concluded more research was necessary, Westlund said the city drafted the Cell Phone Right-To-Know Ordinance because “we wanted to provide people with information if they’re concerned about the issue.”

Assisted by a robot with a gel-filled head, the Federal Communications Commission already tests cell phones and posts the radiation-emission readings on its website. But Westlund and others say that information is difficult to find and that offering it at the point-of-sale will enable consumers to immediately make more informed choices.

“The only way to find that information is by buying a phone and then hope you can find it in the FCC website,” said Alex Formuzis with Environmental Working Group, a research and advocacy group. “But you have to hunt for it like an archaeologist.”