It's never been directly tested in court (not publicly, anyway). The idea is that you can be compelled not to speak about something, but not compelled to speak about it. Forced speech (especially dishonest speech) has never been endorsed by a court.
Still, canaries are a bit complex. You obviously can't prove why one was taken down, because you can't speak about it.
People floated the idea of using long "canary lists" of different things ("haven't received more than one request for user data", "haven't received more than two requests", etc), but there's suspicion that it wouldn't be legal because it would count as revealing specific facts (and you could perhaps be compelled to remove all of them at once). As is, they don't seem to have been rejected or broken, but they have to take the form of one-and-done notices that something happened.
Still, canaries are a bit complex. You obviously can't prove why one was taken down, because you can't speak about it.
People floated the idea of using long "canary lists" of different things ("haven't received more than one request for user data", "haven't received more than two requests", etc), but there's suspicion that it wouldn't be legal because it would count as revealing specific facts (and you could perhaps be compelled to remove all of them at once). As is, they don't seem to have been rejected or broken, but they have to take the form of one-and-done notices that something happened.