Military necessity, along with distinction, and proportionality, are three important principles of international humanitarian law governing the legal use of force in an armed conflict.
[2] Luis Moreno-Ocampo, Chief Prosecutor at the International Criminal Court, investigated allegations of war crimes during the 2003 invasion of Iraq and he published an open letter containing his findings.
International humanitarian law and the Rome Statute permit belligerents to carry out proportionate attacks against military objectives,[1] even when it is known that some civilian deaths or injuries will occur.
The application of Article 8(2)(b)(iv) requires, inter alia, an assessment of: (a) the anticipated civilian damage or injury; (b) the anticipated military advantage; (c) and whether (a) was "clearly excessive" in relation to (b).The judgement of a field commander in battle over military necessity and proportionality is rarely subject to domestic or international legal challenge unless the methods of warfare used by the commander were illegal, as for example was the case with Radislav Krstic who was found guilty as an aider and abettor to genocide by International Criminal Tribunal for the former Yugoslavia for the Srebrenica massacre.
The reason for the prohibition is explained as follows: such projectiles are small and just powerful enough to kill or wound only one man, and as an ordinary bullet will do for this purpose, there is no overriding need for using these inhuman weapons.