OFFICES AND OFFICERS ‑- CITY ‑- MAYOR ‑- POST COMMISSIONER ‑- INCOMPATIBLE PUBLIC OFFICES ‑- SIMULTANEOUS SERVICE AS MAYOR OF FOURTH CLASS CITY AND PORT DISTRICT COMMISSIONER (1) Because of the common law doctrine of incompatible public offices, the same individual may not simultaneously serve as a port district commissioner and as mayor of a town (fourth class city) which is situated entirely within the boundaries of such a district.   (2) Unless an individual who is so serving voluntarily resigns from one or the other of the two incompatible public offices, he will be vulnerable to ouster, from one or the other, by court action; however, based upon the de facto officer doctrine, even though the simultaneous holding of the two offices here in question is not permissible, this does not mean that the past actions of the individual involved in the position which is not retained would thereby be null and void.