120.— The chief executive officer immediately ceases to hold office on—

(a) being nominated as a member of Seanad Éireann,

(b) being elected as a member of either House of the Oireachtas or of the European Parliament,

(c) being regarded, pursuant to section 19 of the European Parliament Elections Act 1997, as having been elected to the European Parliament to fill a vacancy, or

(d) becoming a member of a local authority.