Related Rule
Practice Relating to Rule 155. Defence of Superior Orders
Nigeria’s Manual on the Laws of War provides:
Obedience to an order of a government or of a superior, whether military or civil, or to a municipal law or regulation, affords no defence to a charge of committing a war-crime but may be considered in mitigation of punishment. 
Nigeria, The Laws of War, by Lt. Col. L. Ode PSC, Nigerian Army, Lagos, undated, § 9.
In the Nwaoga case before Nigeria’s Supreme Court in 1972, the appellant and two officers of the rebel Biafran army disguised in civilian clothes went to a town under the control of federal troops and killed an unarmed person. The appellant was convicted of murder. With respect to the plea of superior orders, the Court quoted with approval another judgment, stating:
It was held that a soldier is responsible by military and civil law and it is monstrous to suppose that a soldier could be protected when the order is grossly and manifestly illegal. Of course, there is the other proposition that a soldier is only bound to obey lawful orders and is responsible if he obeys an order not strictly lawful.
In the case before me that order to eliminate the deceased was given by an officer of an illegal regime, his orders therefore are necessarily unlawful and obedience to them involves a violation of the law and the defence of superior orders is untenable. 
Nigeria, Supreme Court, Nwaoga case, Judgment, 3 March 1972.
The Court, however, chose to base its decision on the fact that the accused committed an offence under the Criminal Code, and was liable like any civilian would be, whether or not he was acting under orders. It held that, in the circumstances (operation in disguise, not in the rebel army uniform but in plain clothes, appearing to be members of the peaceful private population), he was liable to punishment since the “deliberate and intentional killing of an unarmed person living peacefully inside the Federal territory … is a crime against humanity, and even if committed during a civil war is in violation of the domestic law of the country, and must be punished”. 
Nigeria, Supreme Court, Nwaoga case, Judgment, 3 March 1972.