Related Rule
New Zealand
Practice Relating to Rule 85. The Use of Incendiary Weapons against Combatants
Section B. The use of incendiary weapons against combatants in particular
New Zealand’s Military Manual (1992) states:
There are no provisions on the use of incendiaries against combatants in [the 1980 Protocol III to the Convention on Certain Conventional Weapons]. The use of incendiary weapons to cause unnecessary suffering is prohibited. A value judgement must be made in particular circumstances to determine whether or not the suffering caused is unnecessary. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, §§ 513(7) and 620(7).
The manual also recalls that:
The UN Conference which negotiated the [1980 Protocol III to the Convention on Certain Conventional Weapons] was unable to agree on any requirement to protect combatants from the effects of incendiary weapons. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 510(f), footnote 49 and § 617(f), footnote 37.