An explosive and newly partially unsealed court filing alleges that the US Department of Homeland Security built up dossiers on ICE observers—including their photos, license plate numbers, and other information—and stored them in a system called the Investigative Case Management database, which was built by Palantir.

Palantir did not immediately respond to requests for comment.

A spokesperson for DHS calls the case “meritless” and says that “the underlying lawsuit is based on the lie that there is a database of ‘domestic terrorists’ run by DHS.”

Plaintiffs allege in the filing, which is heavily based on documents produced by the government and depositions of DHS agents, that agents had a practice of intimidating protesters and observers. They did this, the filing says, by doing drive-bys of the observers’ homes and, in the case of at least one observer, requiring that she be referred to secondary inspection any time she tries to cross the border until at least January 2027.

"The government is treating people who exercise their First Amendment rights and seek to hold it accountable as criminal suspects, and that's what we're asking the court to stop,” says JoAnna Suriani, an attorney at Protect Democracy who is representing ICE observers in the case.

The filing focuses on agents’ conduct during “Operation Catch of the Day,” an immigration enforcement surge in Maine this past January. It is part of a proposed class action brought in federal court in Maine by four observers: Elinor Hilton, Colleen Fagan, Polyxenia Pantos, and Carlyn Williams. It was filed under seal in September, and a redacted version was made public Friday.

In particular, it describes how one DHS agent, referred to as “Agent J.C.” in the filing, used the Investigative Case Management (I...