2 U.S.C. § 1901 - Establishment; officer appointments

There shall be a Capitol police. There shall be a captain of the Capitol police and such other members with such rates of compensation, respectively, as may be appropriated for by Congress from year to year. The captain and lieutenants shall be selected jointly by the Sergeant at Arms of the Senate and the Sergeant at Arms of the House of Representatives; and one-half of the privates shall be selected by the Sergeant at Arms of the Senate and one-half by the Sergeant at Arms of the House of Representatives.