Lots of organizations maintain them. Personally, I have never believed this trick would work. It relies on the fact that a prohibition against speaking doesn't prevent someone from not speaking. But courts generally aren't impressed by this sort of thing, and I can easily imagine a secret warrant that includes a prohibition against triggering the warrant canary. And for all I know, there are right now secret legal proceedings on this very issue.
Australia has sidestepped all of this by outlawing warrant canaries entirely:
Section 182A of the new law says that a person commits an offense if he or she discloses or uses information about "the existence or non-existence of such a [journalist information] warrant." The penalty upon conviction is two years imprisonment.
Expect that sort of wording in future US surveillance bills, too."
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