The nature of the self-defence proportionality requirement

Proportionality as a condition of permissible self-defence remains notoriously controversial inits jus ad bellum sense, despite being subject to rigorous and careful academic consideration.This article provides an extensive reappraisal of proportionality, clarifying why the aim ofhalting an armed attack serves as the primary benchmark against which proportionate self-defence can be measured. In so doing, it critically assesses some of the most recent arguments underpinning criteria other than ‘halting and repelling’ as the primary yard stickfor gauging proportionality. Special attention will be given to Dinstein’s formulation of self-defence, which provides a broad construction of jus ad bellum proportionality with regard to action against large-scale armed attacks. This article further provides a detailed analysis of the subsidiary criteria for the assessment of proportionate self-defence: ‘the effects on civilians’ and ‘choice of targets’, ‘the geographical scope’ and ‘the temporal duration of the conflict’. It clarifies how these criteria ensure that an action carried out on the basis of Article 51 remains proportionate to the aim of defensive force: halting and repelling the attack.