Not exactly sure of the legal situation about canaries, but generally they are constructed as a dead man's switch type situation, where you make a commitment to do something if something else hasn't happened. The idea being that compelling you to act and restraining you from action are two different things.

Given that Reddit has exercised their warrant canary already and other big companies have them, apparently actual lawyers think it's a valid strategy.

In any case, I think that you may be able to play chicken with them over warrant canaries, since the people who use NSLs probably aren't interested in giving anyone standing to challenge them in court.

And yet there are cases where the US constitution leads to this kind of weirdness. Safes in the US use combinations rather than keys (unlike most of the world), because bizarrely enough the authorities can (AIUI) get a warrant that forces you to give up a key, but not (or it's harder) to force you to disclose a combination. So it's not so implausible that there would be a similar legal technicality that was relevant here.

> If you are required not to communicate something, then you don't communicate it. Period.

Legal opinions vary on this subject. Some feel (as you apparently do) that an order not to reveal the receipt of a NSL would require someone to leave a "warrant canary" in place. Others[1] feel that the US legal system does not permit the government to require someone to lie. The only way to find out for sure is for the government to prosecute someone for deleting a warrant canary[2] and either succeed or fail. This has never happened.

Your basic point that "the judicial system isn't stupid, and you can't just violate the rules but with a squirrelly definition and expect to get away with it" is true in general. Your example of insider trading laws is correct. But there are reasonable arguments that a warrant canary is a legitimate legal tactic.

[1] For example, https://www.eff.org/deeplinks/2014/04/warrant-canary-faq

[2] Or to make enough of a threat to do so that the person has standing for a declarative judgement.

This is exactly the approach that CEOs use to get around insider trading laws. It is called "stripping".