In 2008, Illinois passed a law that, a decade later, remains the toughest standard for biometric privacy in the nation. The Biometric Information Privacy Act imposes strict rules on how companies can collect sensitive information from a person’s body, requiring consent before obtaining data like fingerprints.

While other states have since passed similar laws, Illinois’ allows consumers to file lawsuits if they believe their rights have been violated under the law. This week, that led to the start of a major legal battle: the Illinois Supreme Court heard arguments on a challenge to the law that will decide when consumers can take action under the act.

The Illinois Supreme Court is hearing a case

The case centers on the mother of a teenage boy, who brought a suit against Six Flags after her son’s thumbprint was scanned for season pass entry. Lawyers for the family argue that the move violated the law, but the company has said that, since there was no actual harm done by the collection of the print, they aren’t liable.

This week, after rulings from lower courts, the State Supreme Court heard arguments. Whatever the court decides, it could have major ramifications: if consumers have to show they were harmed, privacy advocates argue, it would gut the power of the law. Law360 reports that, at least initially, some of the Supreme Court judges have seemed skeptical of the arguments from the company.

The decision could have consequences for companies well beyond Six Flags. Consumers have used the law to bring suit against tech companies like Facebook, which has faced a legal challenge over its automated photo-tagging tool. The company could theoretically face billions of dollars in fines over the suit.