F.B.I. headquarters in Washington. The F.B.I.’s defiance of a congressional mandate about how it searched for Americans’ information set off a secret court fight.

F.B.I. Practices for Intercepted Emails Violated 4th Amendment, Judge Ruled

Newly declassified files reveal a secret court fight over the F.B.I.’s procedures for searching for Americans’ messages within a warrantless surveillance program’s repository.

nytimes.com