Now it appears that besides massively violating the U.S. Constitution's Fourth Amendment protection against illegal search and seizure, this illegal spying may have put the U.S. at risk by undermining the prosecution of possible terror suspects.
By illegally snooping on people's email and phone conversations, without first making a showing to a judge of some probable cause for the monitoring, the administration has opened the door for defense attorneys to seek new trials for their clients based upon a claim of improperly obtained evidence. Other cases that have yet to be brought to trial may end up being thrown out on the same grounds. ...
"What this means is that George Bush, by violating the rules on domestic surveillance by the NSA, has compromised national security," says Bonifaz. "This scandal effectively prevents the prosecution of people, some of whom may actually be culpable as terrorists."
He explains that as the public learns from public court proceedings just what the extent of the NSA domestic spying campaign has been, and how it has damaged legitimate prosecutions, and as higher courts begin to rule on the impact of and illegality of that campaign, there could be growing calls for impeachment on that issue alone.
http://www.counterpunch.org/lindorff12302005.html