That provision also violated the Constitution because it blocks meaningful judicial review.
Illston isn't the first federal judge to find the letters troubling. The 2nd U.S. Circuit Court of Appeals in New York also found the gag order unconstitutional, but allowed the FBI to continue issuing them if it made changes to its system such as notifying recipients they can ask federal judges to review the letters.
Illston ruled Friday that it's up to Congress, and not the courts, to tinker with the letters.
In 2007, the Justice Department's inspector general found widespread violations in the FBI's use of the letters, including demands without proper authorization and information obtained in non-emergency circumstances. The FBI has tightened oversight of the system.
The FBI made 16,511 national security letter requests for information regarding 7,201 people in 2011, the latest data available. The FBI uses the letters to collect unlimited kinds of sensitive, private information like financial and phone records.
The DOJ didn't immediately respond to a request for comment.