Mary Ellen O’Connell, Robert and Marion Short Professor of Law and Research Professor of International Dispute Resolution–Kroc Institute, University of Notre Dame
One of the most important points that David Kretzmer makes in his detailed analysis of the principle of proportionality in the jus ad bellum is the following: The question of “[p]roportionality arises … only when the aim or ends pursued [through resort to military force] are legitimate. When it comes to state liability, if those ends are illegitimate all forcible measures used will ipse facto be illegitimate, whether they are proportionate or not.” The ends of military force are legitimate only if they conform to an exception to the United Nations Charter Article 2(4) prohibition on the use of force, meet the requirements of the law of state responsibility, and comply with the general principle of necessity. Proportionality involves weighing the cost of resort to military force in terms of lives lost and property destroyed relative to the value of the legitimate military end. Assessing proportionality as a distinctive requirement of lawful resort to force only makes sense when the other conditions on lawful resort to force are also met.
Little wonder, therefore, that we have few if any actual cases that turn specifically on compliance with the principle of proportionality. There are very few examples of post-1945 resort to military force that lend themselves to proportionality assessment because we have so few examples of lawful resort to military force.
Judith Gardam has pointed to one of the only true cases presenting a possible violation of ad bellum proportionality where the other conditions for resort to force were generally met. She has questioned the extent of the use of military force in the liberation of Kuwait during the 1990-1991 Gulf War. In August 1990, Iraq violated Article 2(4) of the United Nations Charter by invading Kuwait and claiming to re-absorb it as Iraq’s long-lost “19th province”. Kuwait’s own small armed forces made some attempt to defend the nation as was their right under Article 51 but were quickly overwhelmed. The UN Security Council became involved and after a period of attempting to use economic sanctions to persuade Iraq to withdraw, authorized a coalition of states to use force to liberate Kuwait. The coalition forces quickly drove Iraq’s armed forces out of Kuwait and drove them beyond a swath of territory that became a demilitarized zone for Kuwait’s future security. Famously, the coalition did not proceed to Baghdad to remove Saddam Hussein from power, because doing so, in the view of coalition leaders was not necessary to the liberation of Kuwait. (The U.S. Secretary of Defense of the time, Richard Cheney, had advocated regime change, nevertheless, and continued to do so until 2003.)
Fighting unrelated to the liberation of Kuwait could not be justified under the principle of necessity since it was clearly beyond the force necessary to remove the occupier. Failing to respect the principle of necessity would make any killing and destruction both unnecessary and disproportionate. Gardam asks whether the amount of force used in the actual liberation of Kuwait—the force employed to drive Iraq’s military forces back behind the internationally recognized boundary was excessive when measured against the force actually needed to achieve this legitimate end.
The distinctive importance of the principle of proportionality is uniquely found when killing and destruction is excessive despite being carried out as part of a military strategy that meets the principle of necessity.
Two other recent cases of lawful resort to military force further illustrate this point. The United States and the United Kingdom began fighting in Afghanistan on 7 October 2001. The two states indicated that the legal basis of the resort to force was Article 51 self-defense on the basis of the Security Council’s Resolution 1368 and a British White Paper making the case for Afghanistan’s state responsibility with respect to the 9/11 attacks. The White Paper argued that the acts of al Qaeda could be attributed to the Taliban government given the close association of the two groups. Attribution of this type is required for the use military force on the territory of a sovereign state. (We must now question the attribution, given subsequent evidence and given the high standard of attribution that ICJ found is required for the resort to force in self-defense against a state for the acts of a non-state actor group.) The Taliban lost Kabul in December 2001, and the further use of force by the U.S. and UK is difficult to justify under the principle of necessity. Even if the necessity of continued fighting could be shown, the question of proportionality would arise—such as the question of whether the use of high aerial bombardment caused disproportionate numbers of deaths respecting whatever the military objective was after the fall of the Taliban. By mid-2002, with Hamid Karzai’s elevation to the leadership of Afghanistan, the armed conflict in self-defense became a counter-insurgency.
In March 2011, the Security Council authorized NATO members and other states to use military force to protect civilians in the Libyan civil war. It seemed clear soon after NATO began attacks in Libya that the alliance’s military objective aimed at ending the regime of Muammar Ghaddafi. Russia and China argued that fighting to change the regime exceeded the Security Council’s mandate and was thus resort to unlawful force. Britain and France countered by saying that ending the regime was necessary to protect civilians. Only if this last point were correct, would the legal assessment move on to the proportionality of the use of military force. Given that 30,000 people died, many, if not most, civilians, in about six months, the cost of pursuing the regime change military objective appears to have been disproportionate to the value of the military objective. The states intervening in Libya seem to have given little attention to the factors of necessity or proportionality.
Professor Kretzmer restricts his discussion of proportionality to the use of force in self-defense. He, therefore, does not reach the Libya case, but it is important to emphasize that necessity and proportionality are general principles of law. They apply to all coercive measures in international relations—whether those measures involve economic sanctions, counter-measures, armed force below the threshold of Article 2(4) of the Charter, or military force that is prohibited by Article 2(4), absent a permissive exception. Necessity and proportionality thus apply to uses of force whether in legitimate self-defense, authorized by the Security Council, or pursuant to an invitation by a government in effective control that is fighting to suppress an insurgency.
Careful readers of Professor Kretzmer’s article will note that I have used a somewhat different test of ad bellum proportionality than he does. He prefers a “means-ends” test, but this test is more appropriate, in my view, for assessing the necessity of resort to force. Proportionality requires weighing the cost of using military force to accomplish a legitimate end. The jus ad bellum test of proportionality uses similar terms to the jus in bello test of proportionality. The essential difference is that the jus ad bellum test is at the outset of a resort to military force and applies to the general plan or strategy to accomplish the legitimate end. It must, logically, apply until the end is accomplished or abandoned.
Another important point respecting necessity and proportionality not mentioned by Professor Kretzmer is the link between the requirements of necessity and proportionality and the requirement of armed attack in Article 51. Article 51 clearly requires that a state acting in self-defense be responding to an actual armed attack. Shaping the response so that it “halts and repels” an attack, requires knowing the nature of the attack. I agree with Enzo Cannizzaro, Olivier Corten, Yoram Dinstein, Christine Gray, Georg Nolte, John Quigley and others that force in self-defense requires evidence of an actual armed occurring. Deciding on a “necessary and proportionate” defense is pure conjecture without evidence of an armed attack. Even where there has been an armed attack, without evidence of more such attacks in proximity to the initial attack, the defending state will have difficulty meeting the necessity and proportionality requirements.
South Korea’s conduct with respect to the intermittent attacks from North Korea over the years provides an excellent example of lawful conduct. Despite the many attacks presumed or proven to be from North Korea, including one that sank the Cheonan, South Korean leaders have respected the legal limits on counter-attacks. They have succeeded in avoiding another major armed conflict for almost 60 years as a result. They have built a prosperous and democratic society in the conditions of peace.
These comments on the rules regulating the use of force, especially the principle of proportionality, are based on a faithful reading of the Charter, its drafting history, decisions of the International Court of Justice, the United Nations World Summit Outcome Document of 2005, and state practice. They are made at a time when the advocacy in certain countries for expanding the right to engage in military force in defiance of this authority is finally waning. The changing mood may be owed to renewed interest in respect for the rule of law in the world. It is also likely to be connected to the realization of the true cost of resort to military force under thin or non-existent justifications. This certainly seems to be the case in the United States following the Afghanistan War, the Iraq War, and the so-called “global war on terror.” The interest in reading exceptions into the Charter and finding the principles of necessity and proportionality open to flexible interpretations, justifying almost any resort to force, may finally be ending as we are forced to count the many costs of waging unlawful war.