David continued the conversation on the compatibility of Cheney's assertion that the Vice President is not part of the Executive Branch and his support for the theory of the Unitary Executive by posing a couple of questions. Given that I've done my best to show the theoretical consistency of those positions, I'll take a crack at responding.
David, you first suggest that if the Vice President is part of the legislative branch, then his participation in executive branch affairs would seem to run afoul of the Supreme Court's stance against congressional encroachment on executive power. I think you overlook a pretty important distinction:
In the Supreme Court's cases (and in the D.C. Circuit decision you mentioned,
FEC v. NRA Political Victory Fund
, 6 F.3d 821 (D.C. Cir. 1993)), the courts stood athwart congressional attempts to "aggrandize" power not afforded Congress by the Constitution. In
NRA Political Victory Fund
, the D.C. Circuit went so far as to state (without offering any on-point citation) that "the mere presence of agents of Congress on an entity with executive powers offends the Constitution."
Even assuming that the D.C. Circuit's statement can be taken as being co-extensive with the Supreme Court's precedents (I think the D.C. Circuit's statement is a bit more aggressive), Vice Presidential participation at the invitation of the President seems to me not to raise the red flags identified in the case law. A Vice President's ad hoc participation in formulation of Administration policy occurs only where the President allows it. Thus, the President's invitation to the Vice President to participate in Administration policymaking involves no threat of congressional "encroachment" on the executive -- the executive remains in full control of the arrangement!
Similarly, where the D.C. Circuit warned (with respect to ex officio congressional members on the FEC) that "their mere presence as agents of Congress conveys a tacit message to the other commissioners," Vice Presidential involvement in Administration policymaking deliberations raise no such concerns. In such cases, the Vice President isn't acting "as [an] agent of Congress" -- he's acting as an agent of the President!
Your second question asked how the Vice President, if a member of the Legislative Branch, could refuse to disclose information to Congress (your case in point: the Cheney Energy Task Force). My answer here is similar to my answer to your first question: for purposes of Presidential privilege and confidentiality, the important question is not whether the Vice President enjoys the privilege, but whether the
enjoys the privilege, and whether the vice-presidential communications were undertaken for the purpose of collecting and conveying to the President information for the President's decision-making process. The fact that a member of the legislative branch is a party to confidential policy meetings convened for the purpose of providing advice to the President does not -- so far as I know -- defeat the privilege. (On that point, though, I'm happy to be corrected.)
Finally, a clarification: You and I disagree slightly on the Vice President's constitutional pedigree: You say that his office "is truly a mix of the branches," but my hypothesis has been that his office is just part of the Legislative Branch. Maybe that's why, contrary to your point, I'm a "Unitarian" who feels comfortable with the Vice President's "complex" nature.