Could a lawyer or someone with familiarity with warrants like these explain how a "warrant canary" is legal?
I understand the concept, but discloses something you can't disclose. They can compel you to lie/not comment if asked, "Hey, Apple, did you get any of those National Security Letters".
Is there a clear cut loophole or is this something yet to be challenged?
It has nothing to do with being compelled to lie by a court order. It has nothing to do with the Judicial system at all. It has nothing to do with lying vs. not commenting.
IANAL (and not an American citizen to begin with!) but most laws are formal, that's how they're compatible with "freedom". For a law to forbid you to do something, it has to describe what actions are exactly forbidden, in a fairly precise language.
A legal system can't let law enforcement officials decide after the fact what's permitted and what isn't (that's the theory anyway; your actual experience may vary widely).
So if a law forbids you to tell something, but doesn't explicitly forbid you to not tell another thing, the non-telling of which could potentially reveal the thing that's supposed to stay secret, then you can claim that you technically obeyed the letter of the law, if not its spirit.
Well, the US has a dual system; in the US everything eventually ends up being evaluated against a written Constitution (something the UK never had).
And if you look at SCOTUS, many Justices are essentialists (the most famous of which is Antonin Scalia); legal essentialism means sticking to the letter of the law.
So I think what I described is a reasonable explanation of the legal canary, at least from a philosophical point of view.
I understand the concept, but discloses something you can't disclose. They can compel you to lie/not comment if asked, "Hey, Apple, did you get any of those National Security Letters".
Is there a clear cut loophole or is this something yet to be challenged?