Related Rule
New Zealand
Practice Relating to Rule 156. Definition of War Crimes
New Zealand’s Military Manual (1992) states:
The term “war crime” is the generic expression for large and small violations of the laws of warfare, whether committed by members of the armed forces or by civilians. It includes “grave breaches”. These are war crimes which are also major violations of the Geneva Conventions of 1949 or of [the 1977 Additional Protocol I]. “War crimes”, in the broadest sense, include crimes against peace and crimes against humanity of the type prosecuted before the International Military Tribunal at Nuremberg following World War II. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 1701(1).
The manual further provides a long list of “grave breaches” and other war crimes. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, §§ 1702, 1703 and 1704.
The manual also states: “The fact that a particular act is not listed in this Manual as a war crime or grave breach does not preclude its being treated as a war crime if it is in breach of any rule of the customary or treaty law of armed conflict.” 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 1704(6).
With respect to non-international armed conflicts in particular, the manual states:
Although breaches of [the 1977 Additional Protocol II] would amount to war crimes if committed in international armed conflict, both the governmental and rebel authority should treat them as breaches of the national criminal law, since the law concerning war crimes relates to international armed conflicts. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 1824(1).
New Zealand’s International Crimes and ICC Act (2000) defines war crimes as grave breaches of the 1949 Geneva Conventions, other serious violations of the laws and customs of war applicable in international armed conflict, serious violations of common Article 3 of the 1949 Geneva Conventions and other serious violations of the laws and customs applicable in armed conflict not of an international character. 
New Zealand, International Crimes and ICC Act, 2000, Section 11.