Related Rule
Netherlands
Practice Relating to Rule 33. Personnel and Objects Involved in a Peacekeeping Mission
The Military Manual (2005) of the Netherlands states:
It is prohibited deliberately to direct attacks against personnel, equipment, units or vehicles involved in the provision of humanitarian aid or peace missions under the UN Charter, provided that they are entitled to the protection afforded under international law to civilians or civilian objects. 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, § 1068.
Under the International Crimes Act (2003) of the Netherlands, the following is a crime, whether committed in an international or non-international armed conflict:
intentionally directing attacks against personnel, installations, material, units and vehicles involved in … peace missions in accordance with the Charter of the United Nations, as long as they are entitled to the protection given to civilians or civilian objects under the international law of armed conflict. 
Netherlands, International Crimes Act, 2003, Articles 5(5)(o) and 6(3)(c).