RS21314 -- International Law and the Preemptive Use of Force Against Iraq Updated April 11, 2003 Until recent decades customary international law deemed the right to use force and even to go to war to be an essentialattribute of every state. As one scholar summarized: It always lies within the power of a State to endeavor to obtain redress for wrongs, or to gain political or other advantages over another, not merely by the employment of force, but also bydirectrecourse to war. (1) Within that framework customary international law also consistently recognized self-defense as a legitimate basis for theuse of force: An act of self-defense is that form of self-protection which is directed against an aggressor or contemplated aggressor. No act can be so described which is not occasioned by attack or fear ofattack. When acts of self-preservation on the part of a State are strictly acts of self-defense, they are permitted by the lawofnations, and are justified on principle, even though they may conflict with the ... rights of otherstates. (2) Moreover, the recognized right of a state to use force for purposes of self-defense traditionally included the preemptive useof force, i.e., the use of force in anticipation of an attack. Hugo Grotius, the father of international law,stated in theseventeenth century that "[i]t be lawful to kill him who is preparing to kill." (3) Emmerich de Vattel a century later similarlyasserted: The safest plan is to prevent evil, where that is possible. A Nation has the right to resist the injury another seeks to inflict upon it, and to use force ... against the aggressor. It may even anticipatetheother's design, being careful, however, not to act upon vague and doubtful suspicions, lest it should run the risk ofbecoming itself the aggressor. (4) The classic formulation of the right of preemptive attack was given by Secretary of State Daniel Webster in connection withthe famous Caroline incident. In 1837 British troops under the cover of night attacked and sank anAmerican ship, the Caroline , in U.S. waters because the ship was being used to provide supplies to insurrectionists againstBritish rule inCanada headquartered on an island on the Canadian side of the Niagara River. The U.S. immediately protested this"extraordinary outrage" and demanded an apology and reparations. The dispute dragged on for several years beforetheBritish conceded that they ought to have immediately offered "some explanation and apology." But in the courseof thediplomatic exchanges Secretary of State Daniel Webster articulated the two conditions essential to the legitimacyof thepreemptive use of force under customary international law. In one note he asserted that an intrusion into the territoryofanother state can be justified as an act of self-defense only in those "cases in which the necessity of that self-defenseisinstant, overwhelming, and leaving no choice of means and no moment for deliberation." (5) In another note he asserted thatthe force used in such circumstances has to be proportional to the threat: It will be for [Her Majesty's Government] to show, also, that the local authorities of Canada, even supposing the necessity of the moment authorized them to enter the territories of theUnitedStates at all, did nothing unreasonable or excessive; since the act, justified by the necessity of self-defence, mustbe limitedby that necessity, and kept clearly within it. (6) Both elements - necessity and proportionality - have been deemed essential to legitimate the preemptive use of force incustomary international law. (7) However, with the founding of the United Nations, the right of individual states to use force was purportedly curbed. TheCharter of the UN states in its Preamble that the UN was established "to save succeeding generations from thescourge ofwar"; and its substantive provisions obligate Member States of the UN to "settle their international disputes bypeacefulmeans" (Article 2(3)) and to "refrain in their international relations from the threat or use of force against theterritorialintegrity or political independence of any State, or in any manner inconsistent with the Purposes of the UnitedNations"(Article 2(4)). In place of the traditional right of states to use force, the Charter creates a system of collectivesecurity inwhich the Security Council is authorized to "determine the existence of any threat to the peace, breach of the peace,or actof aggression" and to "decide what measures shall be taken ... to maintain international peace and security" (Article39). Although nominally outlawing most uses of force in international relations by individual States, the UN Charter doesrecognize a right of nations to use force for the purpose of self-defense. Article 51 of the Charter provides: Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations, until the Security Councilhastaken measures necessary to maintain international peace and security. (8) The exact scope of this right of self-defense, however, has been the subject of ongoing debate. Read literally, Article 51'sarticulation of the right seems to preclude the preemptive use of force by individual states or groupings of states andtoreserve such uses of force exclusively to the Security Council. Measures in self-defense, in this understanding, arelegitimate only after an armed attack has already occurred. (9) Others contend that Article 51 should not be construed so narrowly and that "it would be a travesty of thepurposes of theCharter to compel a defending state to allow its assailant to deliver the first, and perhaps fatal, blow ...." (11) To read Article51 literally, it is said, "is to protect the aggressor's right to the first strike." (12) Consequently, to avoid this result, someassert that Article 51 recognizes the "inherent right of individual or collective self-defence" as it developed incustomaryinternational law prior to adoption of the Charter and preserves it intact. The reference to that right not beingimpaired "ifan armed attack occurs against a Member of the United Nations," it is said, merely emphasizes one importantsituationwhere that right may be exercised but does not exclude or exhaust other possibilities. (13) In further support of this view, it is argued that the literal construction of Article 51 simply ignores the reality that the ColdWar and other political considerations have often paralyzed the Security Council and that, in practice, states havecontinuedto use force preemptively at times in the UN era and the international community has continued to evaluate thelegitimacyof those uses under Article 51 by the traditional constraints of necessity and proportionality. The followingexamplesillustrate several aspects of these contentions: In 1962 President Kennedy, in response to photographic evidence that the Soviet Union was installing medium range missiles in Cuba capable of hitting the United State, imposed a naval "quarantine" on Cuba in order"tointerdict ... the delivery of offensive weapons and associated material." (14) Although President Kennedy said that thepurpose of the quarantine was "to defend the security of the United States," the U.S. did not rely on the legal conceptofself-defense either as articulated in Article 51 or otherwise as a justification for its actions. Abram Chayes, theLegalAdviser to the State Department at that time, later explained the decision not to rely on that justification asfollows: In retrospect ... I think the central difficulty with the Article 51 argument was that it seemed to trivialize the whole effort at legal justification. No doubt the phrase "armed attack" must beconstruedbroadly enough to permit some anticipatory response. But it is a very different matter to expand it to includethreateningdeployments or demonstrations that do not have imminent attack as their purpose or probable outcome. To acceptthatreading is to make the occasion for forceful response essentially a question for unilateral national decision thatwould notonly be formally unreviewable, but not subject to intelligent criticism, either .... Whenever a nation believed thatinterests,which in the heat and pressure of a crisis it is prepared to characterize as vital, were threatened, its use of force inresponsewould become permissible .... In this sense, I believe that an Article 51 defence would have signalled that theUnited Statesdid not take the legal issues involved very seriously, that in its view the situation was to be governed by nationaldiscretion,not international law. (15) In 1967 Israel launched a preemptive attack on Egypt and other Arab states after President Nasser had moved his army across the Sinai toward Israel, forced the UN to withdraw its peacekeeping force from the Sinaiborder, andclosed the port of Aqaba to Israeli shipping, and after Syria, Iraq, Jordan, and Saudi Arabia all began moving troopsto theborders of Israel. In six days it routed Egypt and its Arab allies and had occupied the Sinai Peninsula, the WestBank, andthe Gaza Strip. Israel claimed its attack was defensive in nature and necessary to forestall an Arab invasion. BoththeSecurity Council and the General Assembly rejected proposals to condemn Israel for its "aggressive"actions. (16) On June 7, 1981, Israel bombed and destroyed a nuclear reactor under construction in Iraq. Assertingthat Iraq considered itself to be in a state of war with Israel, that it had participated in the three wars with Israel in1948,1967, and 1973, that it continued to deny that Israel has a right to exist, and that its nuclear program was for thepurpose ofdeveloping weapons capable of destroying Israel, Israel claimed that "in removing this terrible nuclear threat to itsexistence, Israel was only exercising its legitimate right of self-defense within the meaning of this term ininternational lawand as preserved also under the United Nations Charter." (17) Nonetheless, the Security Council unanimously "condemn[ed]the military attack by Israel in clear violation of the Charter of the United Nations and the norms of internationalconduct"and urged the payment of "appropriate redress." (18) Thus, in both theory and practice the preemptive use of force appears to have a home in current international law. Itsclearest legal foundation is in Chapter VII of the UN Charter. Under Article 39 the Security Council has theauthority todetermine the existence not only of breaches of the peace or acts of aggression that have already occurred but alsoof threatsto the peace; and under Article 42 it has the authority to "take such action by air, sea, or land forces as may benecessary tomaintain or restore international peace and security." These authorities clearly seem to encompass the possibilityof thepreemptive use of force. Less clear is whether international law currently allows the preemptive use of force by anation orgroup of nations without Security Council authorization. That would seem to be permissible only if Article 51 is read notliterally but as preserving the use of force in self-defense as traditionally allowed in customary international law. As noted,the construction of Article 51 remains a matter of debate. But so construed, Article 51 would not preclude thepreemptiveuse of force by the U.S. against Iraq or other sovereign nations. To be lawful, however, such uses of force wouldneed tomeet the traditional requirements of necessity and proportionality. As the examples listed above illustrate, the requirement of necessity is most easily met when an armed attack is clearlyimminent, as in the case of the Arab-Israeli War of 1967. But beyond such obvious situations, as Abram Chayesargued,the judgment of necessity becomes increasingly subjective; and there is at present no consensus either in theory orpracticeabout whether the possession or development of weapons of mass destruction (WMD) by a rogue state justifies thepreemptive use of force. Most analysts recognize that if overwhelmingly lethal weaponry is possessed by a nationwillingto use that weaponry directly or through surrogates (such as terrorists), some kind of anticipatory self-defense maybe amatter of national survival; and many - including the Bush Administration - contend that international law oughtto allow,if it does not already do so, for the preemptive use of force in that situation. (19) But many states and analysts are decidedlyreluctant to legitimate the preemptive use of force against threats that are only potential and not actual on thegrounds thejustification can easily be abused. Moreover, it remains a fact that the international community judged Israel'sdestructionof Iraq's nuclear reactor site in 1981 to be an aggressive act rather than an act of self-defense. Iraq has become an occasion to revisit the issue. Iraq had not attacked the U.S., nor did it appear to pose an imminent threatof attack in traditional military terms. As a consequence, it seems doubtful that the use of force against Iraq couldbedeemed to meet the traditional legal tests justifying preemptive attack. But Iraq may have possessed WMD, andit mayhave had ties to terrorist groups that seek to use such weapons against the U.S. If evidence is forthcoming on bothof thoseissues, then the situation necessarily raises the question that the Bush Administration articulated in its nationalsecuritystrategy, i.e. , whether the traditional law of preemption ought to be recast in light of the realities ofWMD, rogue states, andterrorism. Iraq likely will not resolve that question, but it is an occasion to crystallize the debate.

Summary: On March 19, 2003, the United States, aided by Great Britain and Australia,initiated a military invasion of Iraq. Both the U.S. and Great Britain contended that they had sufficient legalauthority touse force against Iraq pursuant to Security Council resolutions adopted in 1990 and 1991. But President Bush alsocontended that, given the "nature and type of threat posed by Iraq," the U.S. had a legal right to use force "in theexercise ofits inherent right of self defense, recognized in Article 51 of the UN Charter." Given that the U.S. had notpreviously beenattacked by Iraq, that contention raised questions about the permissible scope of the preemptive use of force underinternational law. This report examines that issue as it has developed in customary international law and under theUnitedNations Charter. It will be updated as events warrant. (For historical information on the preemptive use of forceby theU.S., see CRS Report RS21311, U.S. Use of Preemptive Military Force.)