Citizenship by registration
Section 26(1) · 1999 Constitution (2004 edition)
What Constitution says
(1) Subject to the provisions of section 28 of this Constitution, a person to whom the provisions of this section apply may be registered as a citizen of Nigeria, if the President is satisfied that - (a) he is a person of good character; (b) he has shown a clear intention of his desire to be domiciled in Nigeria; and (c) he has taken the Oath of Allegiance prescribed in the Seventh Schedule to this Constitution.
This is the 1999 Constitution as published in 2004. Later amendments aren't included yet, so a section may have changed since.
Original source
Official Gazette · CFRN 1999 official PDF · printed page 31. Original document
Release: draft-c8d50d87fae9. Source scope, review and corrections