No. National security letters can act as gag orders, obligating you not to talk about their existence but you're never required to lie and say you have never be

No. National security letters can act as gag orders, obligating you not to talk about their existence but you're never required to lie and say you have never been served a letter. In that case, you can be cagy (as Google has I believe) and say something on the lines of "I can neither confirm nor deny receiving a NS letter" which of course is double speak for "I have one, and I can't talk about it directly".