(a) No officer of an armed force on active duty may accept employment if that employment requires him to be separated from his organization, branch, or unit, or interferes with the performance of his military duties.

(b)(1) This subsection applies—

(A) to a regular officer of an armed force on the active-duty list (and a regular officer of the Coast Guard on the active duty promotion list);

(B) to a retired regular officer of an armed force serving on active duty under a call or order to active duty for a period in excess of 270 days; and

(C) to a reserve officer of an armed force serving on active duty under a call or order to active duty for a period in excess of 270 days.

(2)(A) Except as otherwise authorized by law, an officer to whom this subsection applies may not hold, or exercise the functions of, a civil office in the Government of the United States—

(i) that is an elective office;

(ii) that requires an appointment by the President by and with the advice and consent of the Senate; or

(iii) that is a position in the Executive Schedule under sections 5312 through 5317 of title 5.

(B) An officer to whom this subsection applies may hold or exercise the functions of a civil office in the Government of the United States that is not described in subparagraph (A) when assigned or detailed to that office or to perform those functions.

(3) Except as otherwise authorized by law, an officer to whom this subsection applies by reason of subparagraph (A) of paragraph (1) may not hold or exercise, by election or appointment, the functions of a civil office in the government of a State (or of any political subdivision of a State).

(4)(A) An officer to whom this subsection applies by reason of subparagraph (B) or (C) of paragraph (1) may not hold, by election or appointment, a civil office in the government of a State (or of any political subdivision of a State) if the holding of such office while this subsection so applies to the officer—

(i) is prohibited under the laws of that State; or

(ii) as determined by the Secretary of Defense or by the Secretary of Homeland Security with respect to the Coast Guard when it is not operating as a service in the Navy, interferes with the performance of the officer’s duties as an officer of the armed forces.

(B) Except as otherwise authorized by law, while an officer referred to in subparagraph (A) is serving on active duty, the officer may not exercise the functions of a civil office held by the officer as described in that subparagraph.

(5) Nothing in this subsection shall be construed to invalidate any action undertaken by an officer in furtherance of assigned official duties.

(6) In this subsection, the term “State” includes the District of Columbia and a territory, possession, or commonwealth of the United States.

(c) An officer to whom subsection (b) applies may seek and hold nonpartisan civil office on an independent school board that is located exclusively on a military reservation.

(d) The Secretary of Defense, and the Secretary of Homeland Security with respect to the Coast Guard when it is not operating in the Navy, shall prescribe regulations to implement this section.