There aren’t easy answers to these questions, as an article in the latest issue of Administrative and Regulatory Law News points out. The article, “Mapping the Contours of the Federal Government,” by John M. Kamensky, writing about the just-issued Sourcebook of United States Executive Agencies, notes that:
. . . [The Sourcebook] authors note that “there is no authoritative list of government agencies” and that “many federal entities do not neatly reside in the executive branch.” . . .
. . . the first section of the report addresses the question “What is a Federal agency?” and comes to no real conclusion because “Congress defines what ‘an agency’ is in relation to particular laws rather than provide one overarching definition.” . . .
Not even the courts have offered a definitive answer; so, the authors developed their own definition . . . They define an agency as “a federal executive instrumentality headed by one or more political appointees nominated by the President and confirmed by the Senate (the instrumentality itself rather than its bureaus, offices or divisions).”