We‘ve talked quite a bit about National Security Letters (NSLs) and how the FBI/DOJ regularly abused them to get just about any information the government wanted with no oversight. As a form of an administrative subpoena — with a built in gag-order — NSLs are a great tool for the government to abuse the 4th Amendment. Recipients can‘t talk about them, and no court has to review/approve them. Yet they certainly look scary to most recipients who don‘t dare fight an NSL. That‘s part of the reason why at least one court found them unconstitutional.