The 9th US Circuit Court of Appeals has blocked a San Francisco law that mandates health warnings on adverts for fizzy drinks and other sugary beverages.

Pronouncing a unanimous ruling, the federal appeals court said that the law violates constitutionally protected commercial speech, reported AP.

The jury also granted a preliminary order that prevents the ordinance from coming into force and sent the case back to a lower court.

The judges wrote that the required warnings “offend plaintiffs’ First Amendment rights by chilling protected speech.”

“These drinks are not safe, and as with cigarettes, we have an obligation to warn people of their health risks.”

Citing the Food and Drug Administration (FDA) statements that sugar is generally recognised as safe when not consumed in excess, the court said that San Francisco’s warning that drinking sweet drinks can cause obesity and other diseases was not based on established fact.

The American Beverage Association welcomed the verdict. It was quoted by the news agency as saying: “We are pleased with this ruling, which affirms there are more appropriate ways to help people manage their overall sugar consumption than through mandatory and misleading messages.

The American Beverage Association is representing Coca-Cola, PepsiCo and others in the case.

San Francisco enacted the law in 2015 that would mandate beverage advertisements to print warnings that drinking sugary drinks contributes to health issues. The San Francisco city attorney’s office said it was evaluating its next move following the decision.

Senator Scott Wiener who prepared the ordinance said: “This fight is not over.

“These drinks are not safe, and as with cigarettes, we have an obligation to warn people of their health risks.”

San Francisco is looking to slash consumption of sweet beverages in a bid to deal with diabetes, obesity, heart disease and tooth decay.