The California law, signed in 2004 by Gov. Arnold Schwarzenegger, takes effect Sunday. Animal-rights activists, who argue force-feeding is cruel to birds, lobbied for the ban.
CIFOG, the group representing the French industry, is planning to take the issue to the World Trade Organization, Radio France Internationale reported. Officials say the government backs them.
The United States is actually not a big market for French foie gras, but CIFOG says the ban gives the product a bad name. Producers argue force-feeding does not harm birds because they have elastic esophagi.
"Since we respect the physiology of the animal, we cannot just let this go without reacting," Marie-Pierre Pe, a spokeswoman said.
In California, meanwhile, restaurants were offering last-minute foie gras binges, the Los Angeles Times reported.
Ken Takayama, chef at Melisse in Santa Monica, said the restaurant has offered a "Foie for All" menu for the past seven months. Even though the price tag is $185, that's what half his diners are now choosing.
"I have never bought so much foie gras in my entire cooking career," Takayama said. "It's just insane."