Understanding military necessity properly involves identifying and distinguishing between the material, normative and juridical contexts within which it appears. Within the juridical context, military necessity functions exclusively as an exceptional clause attached to provisions of the law that envisage its admissibility expressly and in advance. As an exceptional clause, military necessity exempts a measure from certain specific rules of international humanitarian law prescribing contrary action to the extent that the measure was required for the attainment of a military purpose and otherwise in conformity with that law. This definition gives rise to four requirements: (i) that the measure be taken primarily for some specific military purpose, (ii) that the measure be required for the attainment of that purpose, (iii) that the purpose be in conformity with international humanitarian law, and (iv) that the measure itself be otherwise in conformity with that law. The International Criminal Tribunal for the Former Yugoslavia (ICTY) has generated a growing body of jurisprudence on the absence of conditions satisfying exceptional military necessity as an element of several war crimes and crimes against humanity. The ICTY has interpreted military necessity exceptions effectively even in highly complex factual circumstances such as those involving combat-related property destruction in a manner that is broadly consistent with the four requirements just noted. It remains to be seen how the International Criminal Court (ICC) will fare in this regard. The ICC would do well to treat with caution Article 31(1)(c) of its statute, which provides for the exclusion of criminal responsibility for certain acts, including those reasonably taken in defence of property essential to accomplishing a military mission.
Hayashi, Nobuo (2010) Requirements of Military Necessity in International Humanitarian Law and International Criminal Law, Boston University International Law Journal 28 (1): 39–140.