The present volume deals with the contemporary norms of LOIAC (the law of international armed conflict) under customary international law and treaties in force. The purpose is to present – and analyse – LOIAC neither as it was practised in the past nor as it may evolve in the future, but only as it is legally prescribed and actually implemented at present.

LOIAC constitutes a branch of international law, and as such it is binding on all belligerent States. LOIAC must be differentiated from Rules of Engagement (ROE) issued by various countries (sometimes by diverse commands in the same country), or by international organizations, and altered at will. ‘ROE may be framed to restrict certain actions or they may permit actions to the full extent allowable under international law’. Accordingly, a belligerent State – animated by political or other reasons of its own – may opt not to employ in given hostilities some destructive weapons the use of which is lawful under LOIAC (see infra, Chapter 3), or to avoid attacking singular targets constituting legitimate military objectives (see infra, Chapter 4). As long as it is acting within the powers vested in it by LOIAC, a belligerent State may at its discretion indulge in a degree of self-restraint. However, under no circumstances can a belligerent State – through ROE or otherwise – authorize its armed forces to commit acts which are incompatible with international obligations imposed by LOIAC.