A possible billion-dollar class action suit may be in the offing for Facebook after the social media giant failed to persuade a federal appeals court that it had not illegally collected and stored biometric data for millions of Facebook users without their consent.

The suit was originally brought by users in Illinois, a state with strict laws around biometric data privacy.

Jonathan Stempel filed this report for Reuters:

The 3-0 decision from the 9th U.S. Circuit Court of Appeals in San Francisco over Facebook’s facial recognition technology exposes the company to billions of dollars in potential damages to the Illinois users who brought the case.

“This biometric data is so sensitive that if it is compromised, there is simply no recourse,” Shawn Williams, a lawyer for plaintiffs in the class action, said in an interview. “It’s not like a Social Security card or credit card number where you can change the number. You can’t change your face.”

Facebook said it plans to appeal. “We have always disclosed our use of face recognition technology and that people can turn it on or off at any time,” a spokesman said in an email. Google, a unit of Alphabet Inc, won the dismissal of a similar lawsuit in Chicago last December.

The lawsuit began in 2015, when Illinois users accused Facebook of violating that state’s Biometric Information Privacy Act in collecting biometric data. Facebook allegedly accomplished this through its “Tag Suggestions” feature, which allowed users to recognize their Facebook friends from previously uploaded photos.

Writing for the appeals court, Circuit Judge Sandra Ikuta said the Illinois users could sue as a group, rejecting Facebook’s argument that their claims were unique and required individual lawsuits. She also said the 2008 Illinois law was intended to protect individuals’ “concrete interests in privacy,” and Facebook’s alleged unauthorized use of a face template “invades an individual’s private affairs and concrete interests.”