A federal appeals court should curb the government’s abuse of grand jury subpoenas to unmask social media users who criticize lawless immigration enforcement.

That is the message from the ACLU, EFF, and other civil liberties and trade groups who filed a friend-of-the-court brief in a sealed case in the U.S. Court of Appeals for the District of Columbia.

The case involves the government’s investigation of an anonymous Reddit user who commented on a post about an immigration officer in Minnesota. The Department of Homeland Security (DHS) first issued an administrative subpoena to Reddit to unmask the user. When the user challenged the subpoena in court on free speech and statutory grounds ( as many others have ), DHS withdrew it. But then the government obtained a separate grand jury subpoena—a subpoena issued by a prosecutor to gather evidence to present to a grand jury before any criminal charges are filed—for much of the same information.…