10 The Rule of Proportionality

Abstract This chapter expounds on the rule of proportionality as indicated in the two 1977 Additional Protocols and customary law. It recognises the inevitable suffering of civilians when hostilities are raging. By the virtue of the proportionality rule that remains in effect regardless of international or non-international conflict, all parties to armed conflict are prohibited from launching attacks expected to cause excessive civilian harm. The chapter then considers the treaty rule in relation to the customary international humanitarian law (IHL) and international criminal law. It also explores the treaty rules of proportionality in attack under general international law. Intentionally launching a disproportionate attack is considered to be simultaneously a violation of the IHL and a war crime.