Public opposition to Flock Safety’s automated number-plate recognition cameras is growing across the United States, prompting some local authorities to cancel or decline to renew contracts. The issue matters because the systems can track vehicles, locations and potentially people without a warrant, raising concerns about privacy, police misuse and routine mass surveillance.

The Institute for Justice says 93 local governments had terminated such contracts as of Wednesday, while challenging the technology in court and documenting alleged abuses including stalking and wrongful stops. Senator Josh Hawley has also opened an investigation into Flock’s data collection, retention and sharing practices, following a Supreme Court ruling requiring warrants for police to obtain location data.