Nearly 20 groups of Amazon shareholders are pressuring the tech company to stop selling facial recognition technology to law enforcement. In a letter delivered to CEO Jeff Bezos late Friday, the shareholders, many of whom are advocates of socially responsible investing, say they’re concerned about the privacy threat of government surveillance from the tool. Amazon’s technology, called Rekognition and introduced in 2016, detects objects and faces in images and videos. Customers, which include law enforcement in Orlando, Florida and Washington County, Oregon, can upload face databases to automatically identify individuals. In one case, the Washington County sheriff’s office identified persons of interest, including a shoplifter caught on a hardware store’s cameras. The store camera’s image was automatically compared with thousands of photos of individuals processed while entering jail. This speeds up a process that used to rely on manual labor and the memory of police officers to identify people.

The shareholders, which include the Social Equity Group and Northwest Coalition for Responsible Investment, are joining groups such as the ACLU in efforts to stop the company from selling the service — pointing out the risks of mass surveillance. They warn about potential civil and human rights violations, and how Amazon’s involvement could have a negative impact on the company’s stock. The shareholders point to the recent scrutiny of Facebook (FB) over privacy and data as a cautionary tale. “We are concerned the technology would be used to unfairly and disproportionately target and surveil people of color, immigrants, and civil society organizations,” the shareholders write, “We are concerned sales may be expanded to foreign governments, including authoritarian regimes.”  Rekognition can analyze images from any source, meaning appearing in images or videos from any police surveillance tool—including CCTV, body cameras, and drones—could potentially mean being matched against databases. The privacy concerns are obvious and very real as the U.S. employs face recognition in airports, borders and even schools.

This is an issue that has gained even more publicity due to recent scandals involving large companies allowing the private information of individuals to fall into the hands of those wishing to do harm with such information. The most obvious and recent example being the sale of Facebook users’ private information to Cambridge Analytica. Any company that deals with the use of private information must be able to balance the right to privacy that people have with the ability to use such information to create a better user experience.