The law is a lot smarter than this. Any act that tends to disclose the existence of such an order, which could include the publishing of a revised transparency report in reaction to receipt of the warrant, could be construed by a judge as a violation of its confidentiality provisions. The law is very broad on this, and subject to interpretation by the judge.

In short, warrant canaries are no different than taking out a billboard announcing receipt of the warrant. Both are overt acts intended to disclose the warrant, and both are illegal.