U.S. President George Bush decided to skip seeking warrants for international wiretaps because the court was challenging him at an unprecedented rate.
And Orin Kerr clarified:
In my post, I argued that the monitoring probably didn't violate the Constitution (and in particular, the Fourth Amendment), but that it probably did violate FISA. This doesn't mean that the monitoring was legal; it only means that of the two possible grounds that it could be illegal, I think it was probably illegal on one ground but not the other ground.
That's how I read him, but I wanted to pass on his clarification.
It's also worth noting that defense attorneys for most of the people on trial in any sort of terrorism-related case are filing anything they can to find out if illegal taps contributed to any of the evidence against their client.
Illegal taps could put terrorists out on the streets.