The Text
The National Assembly may, subject to the provisions of this section, alter any of the provisions of this Constitution. An Act of the National Assembly for the alteration of this Constitution shall not be passed in either House unless the proposal is supported by the votes of not less than two-thirds majority of all the members of that House, and approved by resolution of the Houses of Assembly of not less than two-thirds of all the States.
Source · Constitution of the Federal Republic of Nigeria, 1999, as amended · §9