Related Rule
New Zealand
Practice Relating to Rule 14. Proportionality in Attack
Section A. General
New Zealand’s Military Manual (1992) states: “As a general rule, an attack is not to be carried out if it would result in collateral civilian casualties clearly disproportionate to the expected military advantage.” 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, §§ 517(2) and 630(2).
The manual considers:
The principle of proportionality establishes a link between the concepts of military necessity and humanity. This means that the commander is not allowed to cause damage to non-combatants which is disproportionate to military need … It involves weighing the interests arising from the success of the operation on the one hand, against the possible harmful effects upon protected persons and objects on the other. That is, there must be an acceptable relation between the legitimate destructive effect and the undesirable collateral effects. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 207.
The manual also states that “launching an indiscriminate attack affecting the civilian population or civilian objects in the knowledge that such attack will cause excessive loss of life, injury to civilians or damage to civilian objects” constitutes a grave breach. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 1703(3).
New Zealand’s Geneva Conventions Act (1958), as amended in 1987, provides that “any person who in New Zealand or elsewhere commits, or aids or abets or procures the commission by another person of, a grave breach … of [the 1977 Additional Protocol I] is guilty of an indictable offence”. 
New Zealand, Geneva Conventions Act, 1958, as amended in 1987, Section 3(1).
Under New Zealand’s International Crimes and ICC Act (2000), war crimes include the crime defined in Article 8(2)(b)(iv) of the 1998 ICC Statute. 
New Zealand, International Crimes and ICC Act, 2000, Section 11(2).
In its written statement submitted to the ICJ in the Nuclear Weapons case in 1995, New Zealand stated:
Discrimination between combatants and those who are not directly involved in armed conflict is a fundamental principle of international humanitarian law. While it is prohibited to actually target civilians and civilian objects, there is no absolute protection from collateral damage. The application of the principle requires an assessment of whether the civilian casualties are out of proportion to the legitimate military advantage achieved and whether collateral damage is so widespread as to amount to an indiscriminate attack. 
New Zealand, Written statement submitted to the ICJ, Nuclear Weapons case, 20 June 1995, § 71.