An antifa legal group, in partnership with the American Civil Liberties Union, is trying to prevent Meta from fulfilling a federal subpoena that would unmask the militants behind an anti-Immigration and Customs Enforcement surveillance site.

The Civil Liberties Defense Center, an Oregon law firm dedicated to “defending front-line activists,” filed a motion Tuesday to quash the U.S. Department of Homeland Security’s subpoena seeking user data from Meta, the parent company of Facebook and Instagram, as part of a criminal investigation concerning “officer safety/doxing.”