I'd hire a lawyer that knows how to deal with them and knows how to say no comment.
I've always felt that the warrant canary is a nerd's gotcha designed to get out of a sketchy legal process (NSLs) and that judges would be very unsympathetic. But IANAL.
At least from my perspective, it is not just a "gotcha" problem or whatever feelings it conjures up in a judge's mind.
When a company, who already has a canary in place, receives this kind of warrants, what _can_ the company practically do to comply with non-disclosure? It seems that lying is now the only option left, if the company must explicitly post a "no, we didn't receive such a warrant".
I've always felt that the warrant canary is a nerd's gotcha designed to get out of a sketchy legal process (NSLs) and that judges would be very unsympathetic. But IANAL.