Ala. Code § 36-9-1: How Offices Vacated Generally.

Any office in this state is vacated:

(1) By the death of the incumbent;

(2) By the resignation of the incumbent, except in such cases as are excepted by law;

(3) By the incumbent’s ceasing to be a resident of the state or of the division, district, circuit or county for which he was elected or appointed;

(4) By the decision of a competent tribunal declaring the election or appointment of the incumbent void or his office vacant;

(5) By the act of the Legislature abridging the term of office of the incumbent, when the same is not fixed by the constitution; and

(6) In such other cases as are or may be declared by law.