The nonpartisan Congressional Research Service that's who. Money quote:
A report by Congress's research arm concluded yesterday that the administration's justification for the warrantless eavesdropping authorized by President Bush conflicts with existing law and hinges on weak legal arguments.
The Congressional Research Service's report rebuts the central assertions made recently by Bush and Attorney General Alberto R. Gonzales about the president's authority to order secret intercepts of telephone and e-mail exchanges between people inside the United States and their contacts abroad.