Stop that tag! A judge ruled last week that a US class-action lawsuit arguing that Facebook’s use of its facial recognition tech violates Illinois law will go ahead, despite the company’s attempts to dismiss it.

People upload millions of photos to Facebook every day. The company has used this data to develop powerful artificial intelligence that can identify individual’s faces in photos with more than 97 per cent accuracy. This lets Facebook automatically tag people in your newly uploaded images.

Not everyone is happy with the feature, however. Last year, a group of Facebook users in Illinois filed a civil complaint, claiming that it violated the state’s Biometric Information Privacy Act. BIPA prevents companies from collecting biometric data – such as fingerprints or retina scans – without first developing a clear policy about how the data will be handled, and then obtaining and retaining the user’s consent.

Photos don’t typically fall into the category of biometric data. But the plaintiffs argue that Facebook is effectively creating “faceprints”– digital scans that identify individuals – which should fall under BIPA’s purview.

In the words of the civil complaint: “With millions of its users in the dark about the true nature of this technology, Facebook secretly amassed the world’s largest privately held database of consumer biometric data.”

Facebook tried to dismiss the case, countering that its terms of service bound it only to California and federal laws – not those of Illinois. But on Thursday, a judge dismissed that argument and the case will go ahead.

If Facebook loses it could have big implications for the wider tech industry, which is exploring many different applications for facial recognition, both online and in the real world.

Facebook isn’t the only company facing legal pressure for its face-spotting capabilities. A similar lawsuit was filed in March against Google for faceprints made in its Photos app. And last month, California digital photo company Shutterfly reportedly settled its own case over the Illinois BIPA law.