Section 21: Control of Visitors and Transit Passengers.

(1) An immigration officer may, by notice given at any time to any person who-
(a) has arrived at a recognized port in Nigeria as a visitor or as a transit passenger on board a ship or other water vessel, aircraft, motor vehicle, or other means of transportation, and
(b) is for the time being on board a ship or other water vessel, aircraft, motor vehicle, or other means of transportation :
prohibit him from landing from the ship or other water vessel, aircraft, motor vehicle, or other means of transportation, as the case may be, while he remains at such port or entry point, unless authorized to do so by a superior immigration officer.
(2) An immigration officer may, by notice given at any time to any person who-
(a) lands from a ship or other water vessel, aircraft, motor vehicle, or other means of transportation in contravention of a prohibition imposed on him under sub-section (1) of this Section ;
(b)
being a visitor refused admission, or a transit passenger, remains in Nigeria after the ship or other water vessel. aircraft, motor vehicle, or other means of transportation has left the port of entry ; or
(c)
having been admitted as a visitor into Nigeria subject to a condition restricting the period for which he may remain, remains in Nigeria in contravention of that condition, such person shall, subject to sub-section (3) of this Section, where necessary be treated for the purposes of this Act as if he had been refused admission into Nigeria.
(3)
An immigration officer may, by notice in writing given at any time to any person who has landed or remained in Nigeria as mentioned in sub-section (2) ofthis Section, authorise him to remain in Nigeria either without conditions or subject to conditions the Minister may impose, including in particular, conditions requiring him to leave Nigeria-
(a) in specified ship or other water vessel , aircraft, motor vehicle, or other means of transportation ; or
(b)
within a specified period in accordance with the conditions of his permit or as the case may be, with arrangements made and where such a notice is given to any person, he shall not be treated as a person to whom admission to Nigeria has been refused unless, in the case where he is subject to conditions requiring him to leave Nigeria, he fails to comply or is reasonably suspected of intending to fail to comply with those conditions.
(4) A permit under this section shall be in such form as the Minister may from time to time, prescribe and any permit issued or condition endorsed may at any time be varied or revoked by the Comptroller-General of lmmigration, or such officer may replace the permit in any proper case.