Which leaves open the possibility of the nefarious catch-22 of the pre-emptive NSL: the NSL that threatens you to take down the canary before they have to issue you a substantive NSL!

This is not how an NSL works.

But if you knew how an NSL worked, how could you say?

People see NSA everywhere they want to. Yet, domesric authority here is FBI which compels SIGINT-enabling for NSA per leaks. Court order, NSL, or backdoor are all FBI if coerced.