did Bush break Federal law when he authorized domestic spying operations?

Guess it depends on who you ask. If you ask the Congressional Research Service, they'll carefully state 'it seems so'. From Secrecy News:

The Congressional Research Service has prepared a detailed evaluation of Bush Administration legal claims regarding Presidential authority to conduct warrantless electronic surveillance within the United States.

The CRS authors sift through each of the statutory, constitutional and other arguments that have been presented in defense of the reported NSA surveillance activity, and ultimately find them wanting. A final determination on the matter is impossible, they note, "without an understanding of the specific facts involved and the nature of the President's authorization, which are for the most part classified." In the end, however, "the Administration's legal justification, as presented in the [December 22, 2005] summary analysis from the Office of Legislative Affairs, does not seem to be as well-grounded as the tenor of that letter suggests," they cautiously conclude. See "Presidential Authority to Conduct Warrantless Electronic Surveillance to Gather Foreign Intelligence Information," Congressional Research Service, January 5, 2006: http://www.fas.org/sgp/crs/intel/m010506.pdf