The principle of distinction and military objectives

In its Advisory Opinion of 1996 on Legality of the Threat or Use of Nuclear Weapons, the International Court of Justice recognized the ‘principle of distinction’ – between combatants and non-combatants (civilians) – as a fundamental and ‘intransgressible’ principle of customary international law. The requirement of distinction between combatants and civilians lies at the root of LOIAC. It is reflected in Article 48 of Additional Protocol I of 1977, entitled ‘[b]asic rule’:

There is no doubt that, irrespective of objections to sundry other stipulations of Protocol I, ‘the principle of the military objective has become a part of customary international law for armed conflict’ whether on land, at sea or in the air.

The coinage ‘military objectives’ first came into use in the (non-binding) 1923 Hague Rules of Air Warfare. It was replicated in the 1949 Geneva Conventions (which fail to define it), the 1954 Hague Cultural Property Convention (and especially the 1999 Second Protocol appended to the Hague Convention), as well as the 1998 Rome Statute of the International Criminal Court.

A binding definition of military objectives was crafted in 1977, in Article 52(2) of Protocol I: