Notwithstanding any other provision of law, appointments may be made by the authorized appointing power, including the board of supervisors, to fill any vacancy occurring by reason of the absence of the incumbent on military service from which he has a right to return to his office or position pursuant to the Military and Veterans Code until whichever of the following first occurs: (a) the resigning officer returns to and re-enters the office from which he resigned, or (b) the term expires for which he was elected or appointed.