The state Supreme Court gave the go-ahead Wednesday to an animal-rights group to sue a restaurant that served foie gras, but the suit will proceed only if federal courts reinstate California’s ban on the dish.

Foie gras, made from the enlarged livers of ducks or geese that have been force-fed, was prohibited by the state in a law that took effect in July 2012. Over the next eight months, the Animal Legal Defense Fund sent an investigator undercover to dine three times at Napa’s La Toque restaurant, whose head chef and managing partner, Ken Frank, had been an outspoken opponent of the law.