By Terry Baynes
(Reuters) - Monster Beverage Corp has sued San Francisco's city attorney over an investigation the city launched last year into the safety and marketing of Monster energy drinks.
In the lawsuit filed on Monday in California federal court, the company accused City Attorney Dennis Herrera of violating its constitutional rights by demanding that the company reformulate its drinks and change its product labels and marketing materials.
Energy drinks - caffeinated beverages with aggressive-sounding names like Monster, Red Bull, Rockstar, Amp and Full Throttle - have come under increasing scrutiny from U.S. regulators and politicians over safety concerns.
Last October, Herrera's Consumer Protection Unit launched an investigation into Monster's marketing practices, citing potential health risks that the caffeinated energy drinks pose to young people.
In a March letter, Herrera demanded that the company take immediate steps to lower the caffeine content of its drinks, change its product labels and stop promoting over-consumption, according to court filings.
Monster argues in its suit that the Food and Drug Administration has exclusive authority to regulate the safety of the drinks, and that Herrera's efforts are barred by federal food and drug laws.
In addition, the city attorney's demands violate the company's First Amendment right to free speech, the suit said.
Herrera responded to the company's legal action on Tuesday.
"Monster Energy is claiming an unfettered right to continue marketing its products to children and youth, even in the face of overwhelming evidence that its products pose serious risks to young people's health and safety," Herrera said in a statement.
The lawsuit is Monster Beverage Corp v. Herrera, U.S. District Court, Central District of California, No. 13-786.
(Reporting by Terry Baynes; Editing by Chris Gallagher)