They could bring it back but with a catch: "between 1 April 2016 and (today) we have not received any NSLs, etc." But if you're gonna do that, you could do: "Yesterday, (date), we did not revive any NSLs, etc."
But as has been said before, it's undecided if warrent canaries are even legal. So until we get a ruling on wether they are legal or not, we really have no way of knowing what we can and can't do.
