I would suggest there is a much cleaner way for the TLAs to make warrant canaries ineffective. Send a warrant to every company that publishes a canary. In a short space of time, no company of any note will have a canary, and the whole point of issuing a canary is defeated.
Too risky-- it would show up in Canary Watch when they all dissapear, and you'd start seeing a lot of new canaries being published by companies who hadn't done it before, which would then all get their own NSLs, and the whole thing would continue to snowball until someone refused to comply with an NSL and the resulting stink would probably kill off NSLs alltogether.
Greater crackdowns on freedom and privacy is exactly what the terrorists want, so the government is giving aid to the enemy.
THIS. ABSOLUTELY.
The optimum committee has no members. -- Norman Augustine