Chapter Six of the Nigeria 1999 Constitution
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The President is responsible for:
*.assenting to and signing Bills
*.referring a Bill back to the National Assembly for reconsideration of the Bill's constitutionality
*.referring a Bill to the Constitutional Court for a decision on the Bill's constitutionality
*.summoning the National Assembly, or Parliament to an extraordinary sitting to conduct special business
*.making any appointments that the Constitution or legislation requires the President to make, other than as head of the national executive
*.appointing commissions of inquiry
*.calling a national referendum in terms of an Act of Parliament
*.receiving and recognising foreign diplomatic and consular representatives
*.appointing ambassadors, plenipotentiaries, and diplomatic and consular representatives
*.pardoning or reprieving offenders and remitting any fines, penalties or forfeitures
*.conferring honours
source:
http://www.waado.org/nigerdelta/documents/ConstitutionalMatters/1999Constitution/ChapterSix.html