Persons deemed to be Nigerian citizens
Section 31 · 1999 Constitution (2004 edition)
What Constitution says
For the purposes of this Chapter, a parent or grandparent of a person shall be deemed to be a citizen of Nigeria if at the time of the birth of that person such parent or grandparent would have possessed that status by birth if he had been alive on the date of independence; and in this section, "the date of independence" has the meaning assigned to it in section 25 (2) of 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 33. Original document
Release: draft-c8d50d87fae9. Source scope, review and corrections