A: The Principle of 'Executive Privilege'

Q: What Is Found Nowhere in the Constitution?

Take a look, it ain't there. Executive Privilege is the presidential equivalent of the childhood rant, "because I don't want to." It is not rooted in law; it is based in the principle that open government is a scourge to secret plots. Executive Privilege is a fantasy.

Why Congress has the obligation to investigate
All cabinet officers are nominated by the President but only placed in office by approval of the Senate. This duel responsibility means that all cabinet departments serve the nation as a whole, both Executive and Legislative branches, not merely the President.

In the specific instance of the firing of federal district attorneys there are indications that the firing decisions were made by Karl Rove, Harriet Meirs, and others within the White House. It is proper for Congress to investigate whether the duties of the Attorney General were usurped by members of the White House staff. The Constitution delegates executive responsibilities to the cabinet departments specifically so that their actions will be in the best interests of the nation, not at the whim of the Presidential underlings.

Insofar as members of the White House staff had usurped the duties of the Attorney General they were operating as de facto members of the Justice Department. As such, those individuals have a duty to report to Congress. Conversely, Congress has a duty to investigate the manner in which individuals who have not taken the Consitutionally required oath had usurped the authority of sworn cabinet officers. It is a dangerous practice when the duties of cabinet officers are exported to unaccountable persons and Congress has the obligation to insure this does not occur.