Related Rule
New Zealand
Practice Relating to Rule 54. Attacks against Objects Indispensable to the Survival of the Civilian Population
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).
New Zealand’s Military Manual (1992) provides that the prohibition to attack, destroy, remove or render useless objects indispensable to the survival of the civilian population
shall not apply to such of the objects covered by it as are used by an adverse Party:
a. as sustenance solely for the members of its armed forces; or
b. if not as sustenance, then in direct support of military action, provided, however, that in no event shall actions against these objects be taken which may be expected to leave the civilian population with such inadequate food or water as to cause its starvation or force its movement. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, §§ 504(3) (land warfare) and 613(3) (air warfare).
New Zealand’s Military Manual (1992) states:
In recognition of the vital requirements of any Party to the conflict in the defence of its national territory against invasion, derogation from the prohibitions contained in paragraph 2 [prohibition to attack, destroy, remove or render useless objects indispensable to the survival of the civilian population] may be made by a Party to the conflict within such territory under its own control where required by imperative military necessity.
As a result of this provision, Parties may no longer embark on a scorched earth policy with the intention of starving civilians, even in their national territory, unless that part of the territory is under their control at the time of devastation: scorched earth is no longer available as an offensive policy. It is still permissible to destroy objects indispensable to the survival of the civilian population in the course of ordinary operations if it is militarily necessary for other reasons, for example, to destroy a wheat field to deny concealment to enemy forces. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 504(5), including footnote 10.