from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
CIVIL OFFICER. The constitution of the United States, art. 2, s. 4,
provides, that the president, vice-president, and civil officers of the
United States, shall be removed from office on impeachment for, and
conviction of treason, bribery, or other high crimes and misdemeanors. By
this term are included all officers of the United States who hold their
appointments under the national government, whether their duties are
executive or judicial, in the highest or the lowest departments; of the
government, with the exception of officers of the army and navy. Rawle on
the Const. 213; 2 Story, Const. Sec. 790; a senator of the United States, it
was decided, was not a civil officer, within the meaning of this clause in
the constitution. Senate Journals, 10th January, 1799; 4 Tuck. Bl. Com.
Appx. 57, 58; Rawle, Const. 213; Serg. on Const. Law, 376; Story, Const.
Sec. 791.