"The program's legal, it's designed to protect civil liberties, and it's necessary," Bush told a White House news conference.
And, if he bothered to get a warrant it would be. Since he lacks a warrant it is a crime, and the reason is clearly outlined here.
The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
See, all the good stuff is here. We have unreasonable searches, warrants, and probable cause all in one easy to read portion. Mr. President, your actions are illegal and your efforts to defend them are disgusting.
Or do you think the constitution doesn't apply any more?
Domestic Spying Bush Fourth Amendment