Related Rule
New Zealand
Practice Relating to Rule 28. Medical Units
New Zealand’s Military Manual (1992) states:
Medical establishments on land … must be respected and protected at all times and must not be attacked …
Medical units are establishments, whether military or civilian, organised for medical purposes, and may be fixed or mobile, permanent or temporary.
It is forbidden to attack civilian hospitals. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, §§ 1007(1) and (2) and 1109(1).
The manual also states that the immunity granted to medical units and transports “ceases once they are used for purposes hostile to the adverse Party and outside their humanitarian purpose”. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 1007(1).
The manual further states:
Civilian hospitals continue to enjoy protection so long as they are not made use of to commit acts harmful to the enemy. In the event of such misuse, however, the hospitals remain protected until due warning, with a reasonable time limit, has been given and remained unheeded. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 1109(2).
The manual further states that “attacking a privileged or protected building” [or the] “use of a privileged building for improper purposes” is a war crime recognized by the customary law of armed conflict. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, 1703(5) and 1704(5).
With respect to non-international armed conflicts in particular, the manual states:
[M]edical units … are to be respected at all times and not made the object of attack … [Such protection] shall cease only if they commit hostile acts outside their humanitarian function. In such circumstances, a warning must be given with, whenever appropriate, a time limit, and protection only ceases if the time limit is unheeded. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 1818(2).
Under New Zealand’s International Crimes and ICC Act (2000), war crimes include the crimes defined in Article 8(2)(b)(ix) and (e)(iv) of the 1998 ICC Statute. 
New Zealand, International Crimes and ICC Act, 2000, Section 11(2).