Legislative powers
Section 4(9) · 1999 Constitution (2004 edition)
What Constitution says
(9) Notwithstanding the foregoing provisions of this section, the National Assembly or a House of Assembly shall not, in relation to any criminal offence whatsoever, have power to make any law which shall have retrospective effect.
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 18–19. Original document
Release: draft-c8d50d87fae9. Source scope, review and corrections