Usually the three letter agencies will send you a National Security Letter. If somebody sends you a NSL you're not allowed to talk about it, which makes it very

Usually the three letter agencies will send you a National Security Letter. If somebody sends you a NSL you're not allowed to talk about it, which makes it very difficult to even tell if the NSL is legal or not because it's very difficult to retain legal counsel with these kinds of matters, and secret courts don't have a whole lot of accountability either.