Nixon sought to invoke "executive privilege". Executive privilege
isthe power claimed by thePresident of the United Statesand other
members of theexecutive branchto resist certainsubpoenasand other
interventions by thelegislativeandjudicial branchesof government.
The concept of executive privilege is not mentioned explicitly in
theUnited States Constitution, but theSupreme Court of the United
Statesruled it to be an element of theseparation of powersdoctrine,
and/or derived from the supremacy of executive branch in its own
area of Constitutional activity
TheSupreme Courtconfirmed the legitimacy of this doctrine inUnited
States v. Nixon, but only to the extent of confirming that there is
a qualified privilege. Once invoked, a presumption of privilege is
established, requiring the Prosecutor to make a "sufficient
showing" that the "Presidential material" is "essential to the
justice of the case."(418 U.S. at 713-14).Chief
JusticeBurgerfurther stated that executive privilege would most
effectively apply when the oversight of the executive would impair
that branch's national security concerns. In the case of Watergate,
national security was NOT the issue at hand.