A federal appeals court blocked San Francisco on [September 10] from requiring cell phone dealers to tell customers the products may expose them to dangerous levels of radiation, saying the city can't force retailers to pass along messages they dispute. The ordinance, the first of its kind in the nation, had been scheduled to take effect last October, but has remained on hold during an industry challenge. It would require retailers to give each cell phone buyer a fact sheet saying the World Health Organization had classified the phones' radio-frequency emissions as a possible carcinogen." The sheet also shows human silhouettes absorbing radiation and suggests protective measures, like wearing headsets, making shorter calls and limiting use by children. Stores would have to put similar messages on large wall posters and on stickers attached to display ads. The U.S. Supreme Court has ruled that the government can require businesses to display factual, undisputed information about their products. The city's lawyers and policymakers will review the ruling before deciding their next steps.