249Certain persons may be prevented from entering or landing

249  Certain persons may be prevented from entering or landing  (1) An officer may:  (a) prevent a person whom the officer reasonably suspects to be an unlawful non‑citizen from leaving a vessel on which the person arrived in Australia; or  (b) prevent a removee or deportee from leaving a vessel on which he or she has been placed; and may take such action and use such force as are necessary for that purpose.  (1AA) An officer may prevent a person from leaving a vessel on which the person arrived in Australia if the officer reasonably suspects that the person:  (a) is seeking to enter the migration zone; and  (b) would, if in the migration zone, be an unlawful non‑citizen.  (1A) To avoid doubt, and without limiting the generality of subsections (1) and (1AA), if a person of a kind referred to in paragraph (1)(a) or subsection (1AA) is on board a vessel (other than an aircraft), the actions that may be taken by an officer under subsections (1) and (1AA) include:  (a) requiring the vessel to travel to a port; and  (b) requiring the person to remain on the vessel until it arrives at the port.  (2) The master of a vessel may, in relation to persons on board the vessel, do all things which an officer is, under subsections (1) and (1AA), authorized to do.