In 2015, Facebook was sued under the Illinois Biometric Information Privacy Act, which requires companies to make a public policy before collecting and storing biometric data, including faces scans, and to lay out how the data will be stored. Facebook has used the technology in its Tag Suggestions feature, which determines whether a photo includes a user’s friends.

The plaintiffs brought suit, arguing that Facebook had failed to meet the requirements of the law. When a lower court certified the suit as a class action, Facebook appealed, arguing that…