Disqualifications (President)
Section 137(1)(a) · 1999 Constitution (2004 edition)
What Constitution says
(a) subject to the provisions of section 28 of this Constitution, he has voluntarily acquired the citizenship of a country other than Nigeria or, except in such cases as may be prescribed by the National Assembly, he has made a declaration of allegiance to such other country; or
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 69–70. Original document
Release: draft-c8d50d87fae9. Source scope, review and corrections