Why, you ask, is president Bush so hysterical to secure immunity to companies like AT&T and Verizon who knowingly and willingly violated the law at the request of the administration, months before Sept 11, 2001?
The answer is pretty simple. These companies are under the juridiction of the Federal Courts and they cannot claim executive privilege. The Separation of Power may allow Bush to say 'no' on document request, but AT&T is not in such a position. AT&T, BellSouth (now AT&T) and Verizon can be compelled by a court to turn over all the information they have about the Bush Administrations domestic spying program. Should the lawsuits go to trial, all this messy stuff could be aired publicly.
And it's very possible that crimes have been committed in this domestic spying mess.
The Bush Administration has asserted a States Secrets privilege to block disclosure but has so far be unsuccessful in this effort (but it's not over as I understand the situation), leaving only a gratuitous Congressional act to save the Bushies from exposure. The impotent Harry Reid has done everything under the sun to please Bush on this issue, but the House has found a little spine.