10 USC § 154. Vice Chairman
(a) Appointment.—(1) There is a Vice Chairman of the Joint Chiefs of Staff, appointed by the President, by and with the advice and consent of the Senate, from the officers of the regular components of the armed forces.
(2) The Chairman and Vice Chairman may not be members of the same armed force. However, the President may waive the restriction in the preceding sentence for a limited period of time in order to provide for the orderly transition of officers appointed to serve in the positions of Chairman and Vice Chairman.
(3) The Vice Chairman serves at the pleasure of the President for a term of two years and may be reappointed in the same manner for two additional terms. However, in time of war there is no limit on the number of reappointments.
(b) Requirement for Appointment.—(1) The President may appoint an officer as Vice Chairman of the Joint Chiefs of Staff only if the officer—
(A) has the joint specialty under section 661 of this title; and
(B) has completed a full tour of duty in a joint duty assignment (as defined in section 664(f) of this title) as a general or flag officer.
(2) The President may waive paragraph (1) in the case of an officer if the President determines such action is necessary in the national interest.
(c) Duties.—The Vice Chairman performs the duties prescribed for him as a member of the Joint Chiefs of Staff and such other duties as may be prescribed by the Chairman with the approval of the Secretary of Defense.
(d) Function as Acting Chairman.—When there is a vacancy in the office of Chairman or in the absence or disability of the Chairman, the Vice Chairman acts as Chairman and performs the duties of the Chairman until a successor is appointed or the absence or disability ceases.
(e) Succession After Chairman and Vice Chairman.—When there is a vacancy in the offices of both Chairman and Vice Chairman or in the absence or disability of both the Chairman and the Vice Chairman, or when there is a vacancy in one such office and in the absence or disability of the officer holding the other, the President shall designate a member of the Joint Chiefs of Staff to act as and perform the duties of the Chairman until a successor to the Chairman or Vice Chairman is appointed or the absence or disability of the Chairman or Vice Chairman ceases.
(f) Grade and Rank.—The Vice Chairman, while so serving, holds the grade of general or, in the case of an officer of the Navy, admiral and outranks all other officers of the armed forces except the Chairman. The Vice Chairman may not exercise military command over the Joint Chiefs of Staff or any of the armed forces.