In the letter circulating the company, which was obtained by Gizmodo, employees wrote that they are “troubled by the recent report from the ACLU exposing our company’s practice of selling AWS Rekognition, a powerful facial recognition technology, to police departments and government agencies.”

Rekognition was released in 2016, and according to an Amazon blog post from that year, Rekognition can scan and recognize images including people, pets, scenes and objects.

“You can use Rekognition in several different authentication and security contexts,” the blog post explains. “You can compare a face on a webcam to a badge photo before allowing an employee to enter a secure zone. You can perform visual surveillance, inspecting photos for objects or people of interest or concern.”

In a May letter to Bezos, the American Civil Liberties Union along with more than three-dozen other organizations demanded that Amazon stop selling Rekognition services to law enforcement agencies. The ACLU also released documents and a report criticizing Amazon’s marketing to law enforcement, and Rekognition’s use at a police department in Orlando, Florida and the Washington County Sheriff’s Office in Oregon.

The letter from Amazon employees to Bezos also cites President Donald Trump’s “zero tolerance” policy at the U.S. border as a cause for consternation.

“In the face of this immoral U.S. policy, and the U.S.’s increasingly inhumane treatment of refugees and immigrants beyond this specific policy, we are deeply concerned that Amazon is implicated, providing infrastructure and services that enable ICE and DHS,” the letter reportedly states.

Amazon employees also called for the company to not provide services to companies — like Palantir — that partner with Immigration and Customs Enforcement. Fortune contacted Palantir for comment.

Employees are not alone in voicing their unease. Earlier this week, 19 Amazon shareholders wrote a letter (which was posted publicly by the ACLU) to Bezos about Rekognition. It reads in part:

“In addition to our concerns for U.S. consumers who may be put in harm’s way with law enforcement’s use of Rekognition, we are also concerned sales may be expanded to foreign governments, including authoritarian regimes. Without protective policies in place, it seems inevitable the application of these technologies will result in Amazon’s Rekognition being used to identify and detain democracy advocates.”

When reached for a comment, Amazon pointed Fortune to a blog post written by Dr. Matt Wood, general manager of artificial intelligence at AWS, following the release of the ACLU report:

“Each organization choosing to employ technology must act responsibly or risk legal penalties and public condemnation.” Wood wrote. “AWS takes its responsibilities seriously. But we believe it is the wrong approach to impose a ban on promising new technologies because they might be used by bad actors for nefarious purposes in the future. “

The Amazon employees’ letter is the latest in a trend of employees at large tech companies sharing ethical concerns about the use of products. Employees at both Google and Microsoft have recently objected to contracts with the Department of Defense and ICE, respectively. Google said it would not renew its contract with the DoD. Microsoft discussed its contract with ICE in an email to employees.