From Wilkipedia:
US v. Nixon
The Supreme Court addressed 'executive privilege' in United States v. Nixon, the 1974 case involving the demand by Watergate special prosecutor Leon Jaworski that President Richard Nixon produce the audiotapes of conversations he and his colleagues had in the Oval Office of the White House in connection with criminal charges being brought against members of the Nixon Administration. Nixon invoked the privilege and refused to produce any records.
The Supreme Court did not reject the claim of privilege out of hand; it noted, in fact, "the valid need for protection of communications between high Government officials and those who advise and assist them in the performance of their manifold duties" and that "[h]uman experience teaches that those who expect public dissemination of their remarks may well temper candor with a concern for appearances and for their own interests to the detriment of the decisionmaking process." This is very similar to the logic that the Court had used in establishing an "executive immunity" defense for high office-holders charged with violating citizens' constitutional rights in the course of performing their duties.
The Supreme Court however rejected the notion that the President has an "absolute privilege." The Supreme Court stated: "To read the Article II powers of the President as providing an absolute privilege as against a subpoena essential to enforcement of criminal statutes on no more than a generalized claim of the public interest in confidentiality of nonmilitary and nondiplomatic discussions would upset the constitutional balance of 'a workable government' and gravely impair the role of the courts under Article III." Because Nixon had asserted only a generalized need for confidentiality, the Court held that the larger public interest in obtaining the truth in the context of a criminal prosecution took precedence.
The U.S. attorney firings by the Bush administration potentially violates the Hatch Act, which states in part:
Federal and D.C. employees may not-
use official authority or influence to interfere with an election
solicit or discourage political activity of anyone with business before their agency
solicit or receive political contributions (may be done in certain limited situations by federal labor or other employee organizations)
be candidates for public office in partisan elections
engage in political activity while:
on duty
in a government office
wearing an official uniform
using a government vehicle
wear partisan political buttons on duty
The assertion by the administration that illegal acts as defined by the Hatch Act can be shielded from judicial scrutiny by executive privilege is an asinine and unsupported argument.