SAN FRANCISCO (CBS SF) — A federal appeals court Tuesday ordered a preliminary injunction blocking a San Francisco law that required advertisements for sodas and other sugary drinks to carry a health warning label.

A three-judge panel of the 9th U.S. Circuit Court of Appeals in San Francisco said the law burdened the free-speech rights of soda advertisers.

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The city law required the warning message to occupy 20 percent of the space on a label or advertisement.

The appeals court agreed with the American Beverage Association’s argument that a warning of that size would overwhelm any messages the companies wanted to present.

Two of the three judges on the panel also said the city’s warning was misleading because it didn’t explain that soda is not the only source of sugar in Americans’ diet and that research indicates that over-consumption of sugar, rather than moderate consumption, is harmful.

“By focusing on a single product, the warning conveys the message that sugar-sweetened beverages are less healthy than other sources of added sugars and calories,” Circuit Judge Sandra Ikuta wrote.

“This message is deceptive in light of the current state of research on this issue,” Ikuta wrote.

The city law, enacted in 2015, would have required ads and labels to state: “WARNING: Drinking beverages with added sugar(s) contributes to obesity, diabetes, and tooth decay. This is a message from the City and County of San Francisco.”

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The measure was challenged by the Washington, D.C.-based American Beverage Association, the California Retailers Association and the California State Outdoor Advertising Association.

The appeals court overturned a decision in which U.S. District Judge Edward Chen of San Francisco declined to grant a preliminary injunction last year. Chen concluded that the warning was “factual and accurate” and that the city was within its rights to seek to protect public health.

Beverage association spokesman William Dermody said, “Today’s decision affirms our position that the San Francisco warning mandate not only violates the constitutional right to free speech but it is also deceptive and misleading to consumers.”

Dermody said beverage companies are seeking better ways to help Americans reduce sugar consumption, including offering choices with less sugar and providing calorie information so that people can make informed decisions.

John Cote, a spokesman for City Attorney Dennis Herrera, said, “We’re disappointed. We’re analyzing the decision and evaluating all of our options.

“San Francisco is committed to remaining a leader in protecting health, especially when it comes to protecting the health of children,” Cote said.

The ruling could be appealed to an expanded 11-judge panel of the appeals court or to the U.S. Supreme Court. If it is not successfully appealed, the case would go back to the trial court for entry of a preliminary injunction.

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