US VP No Longer a Part of the US Government?

An editorial in the San Diego Union--- titled “Is he vice president? Or king?”---quotes the Associated Press:

Cheney's office -- over the objections of the National Archives -- has exempted itself from a presidential executive order that seeks to protect national security information generated by the government, according to the House Committee on Oversight and Government Reform.

Under the order, executive branch offices are required to give the Information Security Oversight Office at the archives data on how much material it has classified and declassified.

Cheney's office provided the information in 2001 and 2002, then stopped. Henry Waxman, chairman of the committee, said Cheney's office claims it need not comply with the executive order because it is not an "entity within the executive branch."

This story is actually getting some play in mainstream news venues in the US, with a focus on Waxman’s revelation that Cheney’s staff tried to have the Information Security Oversight Office abolished altogether. What I’m wondering, though, is whether the vice president considers his office a part of the US Government at all. What other branch of government could it belong to besides the executive branch? Surely not the judicial or congressional branches. And these are the only branches of government set forth in the US Constitution. The title of the San Diego Union’s editorial is facetious, but I’ve got to wonder why Cheney is characterizing himself and his office as no longer a part of the government.