[Jtsummers]

> What exactly makes the GAO not "part of the executive branch" ?

https://www.law.cornell.edu/uscode/text/31/702

>> (a)The Government Accountability Office is an instrumentality of the United States Government independent of the executive departments.

The law establishing it also establishes it as independent.

[mindslight]

Sure, that is what is written down. But as a necessary part of its operation, there is a whole lot of executive power being exercised as well, which the unitary executive theory says would fall under the authority of the president.