So you want them to tell Mahmoud Ibn Bin Maktoub the mad bomber to hold on the line while they get a warrant?
Interesting, thanks.
Nope. They don't need to. That FISA law allows them to go ahead without a warrant, and they have 72 hours (after the fact) to request the warrant. The law has allowances for situations where you don't have time to stop and get the warrant.
I think they should definitely do the wiretap in an emergency situation without the warrant, but they should then follow the law (and cover their butts) by submitting for the warrant within 72 hours. That FISA court never rejected any requests in 2004. They granted every single warrant. So why didn't they do this?