U.S. District Judge James Donato ruled on Monday that Facebook must face a class-action lawsuit alleging that the social network unlawfully used a facial recognition process on photos without user permission. Donato ruled that a class-action was the most efficient way to resolve the dispute over facial templates. KFGO reports: Facebook said it was reviewing the ruling. "We continue to believe the case has no merit and will defend ourselves vigorously," the company said in a statement. Lawyers for the plaintiffs could not immediately be reached for comment. Facebook users sued in 2015, alleging violations of an Illinois state law about the privacy of biometric information. The class will consist of Facebook users in Illinois for whom Facebook created and stored facial recognition algorithms after June 7, 2011, Donato ruled. That is the date when Facebook launched "Tag Suggestions," a feature that suggests people to tag after a Facebook user uploads a photo. In the U.S. court system, certification of a class is typically a major hurdle that plaintiffs in proposed class actions need to overcome before reaching a possible settlement or trial.