structural:summarization
Constitutional provisions

The Constitution gives Congress the authority to impeach and remove "The President, Vice President, and all civil Officers of the United States" upon a determination that such officers have engaged in treason, bribery, or other high crimes and misdemeanors. The Constitution does not articulate who qualifies as a "civil officer of the United States". Federal judges are subject to impeachment. Within the executive branch, any presidentially appointed "principal officer", including a head of an agency such as a secretary, administrator, or commissioner, is a "civil officer of the United States" subject to impeachment. At the opposite end of the spectrum, lesser functionaries, such as federal civil service employees, do not exercise "significant authority", and are not appointed by the president or an agency head. These employees do not appear to be subject to impeachment, though that may be a matter of allocation of House floor debate time by the Speaker, rather than a matter of law.