Related Rule
Practice Relating to Rule 7. The Principle of Distinction between Civilian Objects and Military Objectives
Section A. The principle of distinction
Nigeria’s Military Manual (1994) provides: “For both the conduct of operations and behaviour in action, the main aim for all commanders and individual combatants is to distinguish combatants and military objectives from civilian persons and objects at all times.” 
Nigeria, International Humanitarian Law (IHL), Directorate of Legal Services, Nigerian Army, 1994, p. 41, § 9.
According to the Report on the Practice of Nigeria, it is Nigeria’s opinio juris that the distinction between civilian objects and military objectives is part of customary international law. 
Report on the Practice of Nigeria, 1997, Chapter 1.3.