According to court records cited by WIRED, 62 HSI agents worked on the case, including 11 undercover operatives.
The investigations, called Project Whipple Shield and Operation Puppet Master, were funded through Operation Keyhole, an HSI undercover program dating to 2008.
Prosecutors say the activists conspired to block immigration enforcement, unlawfully identify and stalk federal agents, and assault them, while defense lawyers say the charges do not match their clients' alleged conduct.
Agents used Reaper drones, infiltrated Signal chats totaling 15 terabytes, and relied on Patriot Act financial-records queries usually tied to terrorism and money laundering.
They also drew on commercial data brokers and cloud and payment records, and photographed and ran the plates of cars at activist meeting sites.
Former law enforcement officials told WIRED the case likely belongs to a wider intelligence effort that began before the administration's December 2025 deployment in Minnesota.
Defense attorney Kevin Riach compares it to the FBI's COINTELPRO, which unconstitutionally targeted civil rights and anti-war groups.
Mike German, a retired FBI agent, noted that a CIA program against the anti-war movement peaked at 42 officers, versus 62 HSI agents here.
Prosecutors have not accepted that characterization, and the legality of the methods is contested.
The operations were authorized under National Security Presidential Memorandum 7, issued after Charlie Kirk's assassination in September, which directs federal law enforcement to use all available tools against groups that criticize administration policy. The full reach of the investigations is unknown. Court filings also show HSI used an administrative summons meant for customs and tax violations to obtain phone records of journalists covering Operation Metro Surge, as first reported by The Guardian. Surveillance extended to activist conferences in Seattle, Michigan, and New York City, and several case agents also appear in prosecutions of activists in other cities. Spencer Reynolds, a former DHS attorney now at the NAACP Legal Defense Fund, said the operation does not appear limited to Minnesota.