Workers at Amazon have demanded that their employer stop the sale of facial recognition software and other services to the US government. In a letter addressed to Amazon CEO Jeff Bezos and posted on the company’s internal wiki, employees said that they “refuse to contribute to tools that violate human rights,” citing the mistreatment of refugees and immigrants by ICE and the targeting of black activists by law enforcement. The letter follows similar protests at Google and Microsoft.

“As ethically concerned Amazonians, we demand a choice in what we build, and a say in how it is used,” says the letter, first reported by The Hill. The employees (it’s not clear how many signed the letter) refer to the sale of computer services by IBM to the Nazis as a worrying parallel. “IBM did not take responsibility then, and by the time their role was understood, it was too late,” says the letter. “We will not let that happen again.”

The employees call out two specific businesses that Amazon should end: the sale of facial recognition software to law enforcement (marketed as Amazon Web Services Rekognition), and the sale of AWS cloud services to Palantir (a data analytics firm that provides “mission critical” software to ICE).

Amazon’s sale of Rekognition software to the police was first revealed by an ACLU investigation in May, with the civil liberties group warning that the deployment of the technology could be the beginning of automated mass surveillance in America. Palantir, meanwhile, has been working with ICE since 2014 under President Obama, and helps the agency manage the stacks of personal data needed to target and deport individuals.

The letter written by Amazon’s employees references the separation of children from their families at the US border as a motivation for the protest. They write: “In the face of this immoral US policy, and the US’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.”

This protest from Amazon is the latest outcry from Silicon Valley workers over work with the US government. In March, it was revealed that Google was helping the Pentagon build AI tools to analyze drone surveillance footage. Employees protested and more than a dozen even resigned, and as a result, Google pulled out of the contract and announced a new pledge not to develop AI weapons. More recently, more than 300 employees at Microsoft demanded that the company stop providing cloud services to ICE. Microsoft CEO Satya Nadella downplayed the work, saying the company was only providing benign software for tasks like messaging and email.

It remains to be seen whether the protests at Microsoft or Amazon will affect the companies’ policies, but the trend of tech workers taking an active stance on their employer’s work with the US government seems unlikely to end anytime soon.

As seen via Gizmodo, you can read the full letter from the Amazon employees below: