Bauer/CTU Violate FISA?

Last night, CTU gets a voice recording of the terrorist who has stolen nerve gas and has threatened to use it to kill Americans. CTU springs into action and scans the "chatter on the NSA satellites" for a voice print match to determine the guy's plans.

Well, they get a match and listen in on a conversation that leads them to the person who will provide a chip to the terrorist. The chip will allow the terrorist to release the gas. This is CTU's one and only lead to the nerve gas.

I don't recall them getting a warrant first......

Granted this is fiction, but did CTU just violate FISA? It was effectively a wire tap without a warrant on a DOMESTIC (both phones on US soil) call.
If polled, how many 24 watchers (I am assuming the viewership cuts across the political spectrum) would say CTU did the right thing? What would Leahy/Kennedy/Biden/Reid/Dean say about such a scenario?

Just curious.