Update: From 2014, but Moxie Marlinspike comments that "every lawyer we've spoken to has confirmed that [warrant canaries] would not work":
> If it's illegal to advertise that you've received a court order of some kind, it's illegal to intentionally and knowingly take any action that has the effect of advertising the receipt of that order. A judge can't force you to do anything, but every lawyer I've spoken to has indicated that having a "canary" you remove or choose not to update would likely have the same legal consequences as simply posting something that explicitly says you've received something.
https://web.archive.org/web/20141027143819/https://github.co...