Related Rule
New Zealand
Practice Relating to Rule 54. Attacks against Objects Indispensable to the Survival of the Civilian Population
Section A. Attacks against objects
New Zealand’s Military Manual (1992) states:
[The 1977 Additional Protocol I] Art. 54 expands the customary protection as follows: …
It is prohibited to attack, destroy, remove or render useless objects indispensable to the survival of the civilian population, such as foodstuffs, agricultural areas for the production of foodstuffs, crops, livestock, drinking water installations and supplies and irrigation works, for the specific purpose of denying them for their sustenance value to the civilian population or to the adverse Party, whatever the motive, whether in order to starve out civilians, to cause them to move away, or for any other motive.
This prohibition does not, however, extend to attacks carried out for some specific purpose other than that of denying sustenance to the civilian population. 
New Zealand, Military Manual (1992), § 504(2) (land warfare), including footnote 9; see also § 613(2) (air warfare).
[emphasis in original]
The manual also states:
[The 1977 Additional Protocol II] forbids starvation as a method of combat: it is prohibited for that purpose to attack, destroy, remove or render useless for that purpose objects considered indispensable to the survival of the civilian population, such as foodstuffs, agricultural areas, livestock, drinking water installations, irrigation works, and the like.
In other words, deprivation of food and other materials necessary to sustain the population cannot be used by a government as a method of pressure against civilians supporting rebels. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 1820, including footnote 75.
Under New Zealand’s International Crimes and ICC Act (2000), war crimes include the crime defined in Article 8(2)(b)(xxv) of the 1998 ICC Statute. 
New Zealand, International Crimes and ICC Act, 2000, Section 11(2).