Outside of spy fiction and conspiracy theories, I haven't seen any evidence that the government can legally force someone to lie (vs just a no comment) in order to cover up an NSL or FISA order.
Is there any evidence that they would able to force a company using a warrant canary to issue a fake one or respond with anything other than "no comment" to direct questions from the media?
http://www.buzzfeed.com/mattlynley/verizons-internal-memo-to...