Bush invoked executive privilege "in substance" in refusing to disclose the details of Vice President Dick Cheney's meetings with energy executives, which was not appealed by the GAO. In a separate Supreme Court decision in 2004, however, Justice Anthony Kennedy noted "Executive privilege is an extraordinary assertion of power 'not to be lightly invoked.' United States v. Reynolds, 345 U.S. 1, 7 (1953).
"Once executive privilege is asserted, coequal branches of the Government are set on a collision course. The Judiciary is forced into the difficult task of balancing the need for information in a judicial proceeding and the Executive’s Article II prerogatives. This inquiry places courts in the awkward position of evaluating the Executive’s claims of confidentiality and autonomy, and pushes to the fore difficult questions of separation of powers and checks and balances. These 'occasion for constitutional confrontation between the two branches' are likely to be avoided whenever possible. United States v. Nixon, supra, at 692."[9]
Further, on June 28, 2007, Bush invoked executive privilege in response to congressional subpoenas requesting documents from former presidential counsel Harriet Miers and former political director Sara Taylor,[10] citing that:
The reason for these distinctions rests upon a bedrock presidential prerogative: for the President to perform his constitutional duties, it is imperative that he receive candid and unfettered advice and that free and open discussions and deliberations occur among his advisors and between those advisors and others within and outside the Executive Branch.