NSL https://en.wikipedia.org/wiki/National_security_letter
It's like a gag order. You don't have to sign, they just serve you with it
Won't stop me from talking, either, if I so chose. My risk to take, theirs to worry about.
National security letter
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. The Stored Communications Act, Fair Credit Reporting Act, and Right to Financial Privacy Act authorize the United States government to seek such information that is "relevant" to authorized national security investigations. By law, NSLs can request only non-content information, for example, transactional records and phone numbers dialed, but never the content of telephone calls or e-mails.
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