A national security letter (NSL) is an administrative subpoena issued by the United States government to gather information for national security purposes. NSLs do not require prior approval from a judge. [wikipedia]
While I guess this is something, I would be curious to know what types of users are being targeted with these NSLs, and for what crimes. While it's natural to think "Islamic extremism and terrorism" as that's the usual natsec rallying cry, I wouldn't be surprised to see these being used for other purposes.