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The Limited Necessity of Resort to Force

O’Connell, Mary Ellen. “The Limited Necessity of Resort To Force” in Imagining Law. Dale Stephens and Paul Babie (eds). Adelaide University Press. Forthcoming.

Notre Dame Law School Legal Studies Research Abstract No. 1624

41 Pages Posted: 27 Jun 2016  

Mary Ellen O'Connell

Notre Dame Law School

Date Written: June 27, 2016


In 2004, Judith Gardam published her invaluable book, Necessity, Proportionality and the Use of Force by States. In it she makes the case that all lawful resort to military force at the international level requires compliance with the principles of necessity and proportionality. Prior to her work, discussions of resort to force often overlooked these crucial principles, perhaps in part because of a paucity of expert analysis. Her book has become the standard work on necessity, proportionality, and the use of force. This Chapter has revisited her treatment of necessity in the jus ad bellum in light of the scholarship on necessity in the intervening years. An assessment of this scholarship leads to three propositions, updating Gardam’s work:

1. Necessity is a general principle inherent to the international legal system, meaning that the correct interpretation of necessity has an enduring quality — it does not change, even with changing state practice and opinio juris.

2. Necessity has two meanings in the jus ad bellum: it requires that the use of force be a last resort and that there be a high likelihood that the use of force will succeed in accomplishing the legitimate objective of resorting to force.

3. Necessity is not now, was not in the past, and will not in the future be a basis for the lawful resort to force. States must look to the UN Charter for exceptions to the prohibition on the use of force, not the doctrine of necessity, in the first instance. Necessity then imposes additional conditions on resort to force that, if not met, can prohibit uses of force despite the existence of any lawful basis.

Keywords: necessity, use of force, international law, proportionality, self-defense, humanitarian intervention, Security Council, proportionality

JEL Classification: K33

Suggested Citation

O'Connell, Mary Ellen, The Limited Necessity of Resort to Force (June 27, 2016). Notre Dame Law School Legal Studies Research Abstract No. 1624. Available at SSRN:

Mary Ellen O'Connell (Contact Author)

Notre Dame Law School ( email )

P.O. Box 780
Notre Dame, IN 46556-0780
United States
574-631-7953 (Phone)

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