Executive powers
Section 5(4)(a) · 1999 Constitution (2004 edition)
What Constitution says
(a) the President shall not declare a state of war between the Federation and another country except with the sanction of a resolution of both Houses of the National Assembly, sitting in a joint session; and
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 19–20. Original document
Release: draft-c8d50d87fae9. Source scope, review and corrections