68 No. 2 of 2016] Constitution of Zambia (Amendment) (e) the councillor acts contrary to the code of ethics provided for in Article 155; (f) the councillor has a mental or physical disability that makes the councillor incapable of performing the functions of councillor; or (g) the councillor dies. (3) Where a councillor resigns in accordance with clause (2) (b), (c), (d) and (e) the councillor shall not be eligible for re-election as councillor for the duration of the term of that council. By-election for council 158. (1) Where a vacancy occurs in the office of mayor, council chairperson or councillor— (a) the Town Clerk or Council Secretary of the local authority shall, within seven days of the occurrence of the vacancy, inform the Electoral Commission, in writing, of the vacancy; and (b) a by-election shall be held in accordance with Article 57. (2) If a person is elected to the office of mayor, council chairperson or councillor in a by-election, that mayor, council chairperson or councillor shall serve for the unexpired term of the council and be deemed— (a) to have served a full term as mayor, council chairperson or councillor if, at the date on which the councillor assumed office, at least three years remain before the date of the next general election; or (b) not to have served a term of office as mayor, council chairperson or councillor, if, at the date on which the councillor assumed office, less than three years remain before the date of the next general election. Local government elections tribunals and petitions 159. (1) The Chief Justice shall establish such number of ad hoc local government elections tribunals as are necessary to hear whether— (a) a person has been validly elected as a councillor; or (b) the office of a councillor has become vacant. (2) A local government elections tribunal shall be presided over by a magistrate of competent jurisdiction sitting with two legal practitioners appointed by the Chief Justice.