Related Rule
New Zealand
Practice Relating to Rule 72. Poison and Poisoned Weapons
New Zealand’s Military Manual (1992) prohibits the use of “poison or poisoned weapons”. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 510.
The manual further notes that “the use of poison or poisoned weapons” is “an old-established rule of customary law” which constitutes a war crime. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 1704(2)(a) and footnote 32.
Under New Zealand’s International Crimes and ICC Act (2000), war crimes include the crime defined in Article 8(2)(b)(xvii) 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: “The use of poison and poisoned weapons has long been prohibited. The prohibition is set out in the 1925 Geneva [Gas] Protocol but also forms part of customary law.” 
New Zealand, Written statement submitted to the ICJ, Nuclear Weapons case, 20 June 1995, § 72.