Aerospace Intervention: Justifying 21st Century Air Force Operations   



Lt Col Larry D. Youngner, USAF





Since January 1st, 2000, the US Air Force prosecuted an air war over Serbia and continued enforcement of no-fly zones over Iraq.  In each case, US leaders pursued national security interests by capitalizing on aerospace technological capabilities, global reach, and military advantage.  US aerospace operations over Serbia and Iraq aimed to deny another sovereign state the full use of its own territory, particularly its airspace.  American leadership rationalized these military actions as deterrence of aggression, humanitarian intervention, or both.  What legal authority buttresses the US political decision to engage in aerospace intervention?  The answer requires analysis of just war doctrine in light of the United Nations Charter1 and the traditional law of armed conflict concepts justifying recourse to war or jus ad bellum.2


I.  Just War Theory and Morality


 “Men who take up arms against one another in public war do not cease on this account to be moral beings, responsible to one another and to God.” [3]


                                                                                    —Francis Lieber, 1863


     Many scholars observe that morals and law are not necessarily the same.[4]  They are as streams sprung from one source, flowing often together, often apart, and although ultimately in the same direction, not always over the same terrain.  Just war theory generally judges war on the following criteria: “If the war is declared by legitimate authority (those entrusted with the governance of the nation-state), is embarked upon for a just cause, is waged with the right intention, and employs just means, then that war may be morally justified.”[5]  In turn, the “just cause” element espoused three of its own conditions to meet either singly or collectively to make the cause just: “defense against attack, punishment of evil, or the recovery of something wrongly taken.”[6]    


     Wars should ultimately be fought for one just cause—“to provide a better peace”[7] for our Nation.  The ultimate object of the law of armed conflict is a moral object—humanity.[8] A nation should send its citizens to combat for only the best of reasons.  While combat ensues, human suffering should be minimized.  When conflict subsides, a military service should return the veterans as moral citizens.  In the end, this explains why a law of armed conflict even exists.  As General Telford Taylor most aptly put it:


There are at least two reasons—or perhaps one basic reason with two formulations for the preservation and continued enforcement, as even-handedly as possible, of the laws of war.  The first is strictly pragmatic: They work.  Violated or ignored as they often are, enough of the rules work enough of the time so that mankind is very much better off with them than without them.

     Another and, to my mind even more important basis of the laws of war is that they are necessary to diminish the corrosive effect of mortal combat on the participants.[9]


American society demands just conduct in war fought for just reasons.  What then are the just causes for aerospace intervention?  This paper identifies two main justifications.


II.  Two Just Causes: Protect Fundamental Human Rights and Self-Defense Against Aggression


     Two significant justifications in international law are humanitarian intervention and self-defense.  Secretary of State Daniel Webster defined a renowned self-defense standard in The Caroline incident.[10]  He said, there must be “a necessity of self-defense, instant, overwhelming, leaving no choice of means and no moment for deliberation.”[11]  Besides the customary inherent right of self-defense, the law of armed conflict also developed other rationales for use of force, some better accepted than others.[12] This paper examines both the traditional law of armed conflict and the UN Charter on these two rationales for use of force.


A.  Humanitarian Intervention and the UN Charter—Sovereignty vs. Human Rights


      Perhaps the cornerstone of international relations is the inviolability of the sovereign state.[13]  It is an aspect of sovereignty that the sovereign may treat its people in any fashion.[14]  Yet, nations frequently and historically intervene in other nations for humanitarian purposes.[15]  When does international law pierce the sacrosanct veil of sovereignty to allow another state to intercede on behalf of a persecuted population? 


     Before the Charter, humanitarian intervention was largely accepted as practice among states.[16]  Relying on Vattel, Grotius, Oppenheim, Lauterpacht, and Guggenheim, one finds the historically broad construction of human rights law indicates “the expectations and demands of the peoples of the world in regard to the minimum conditions of humanity.”[17]  The League of Nations held the following pre-UN Charter view:


Some rights are not rights created by States for the benefit of their nationals or of foreigners; namely the right to life, the right to liberty and the right to own property.  …  Before these rights, nationality sinks into the background, because they belong to the man as human being, and are not, accordingly, subordinate to the will of the State.  …  When a state abuses its right of sovereignty by permitting within its territory the treatment of its own nationals or foreigners in a manner violative of all universal standards of humanity, any nation may step in and exercise the right of humanitarian intervention.[18]



     International law scholars divide into two main camps on the lawfulness of humanitarian intervention after the UN Charter entered into force.[19]  One camp, represented by Professor W. Michael Reisman and the New Haven school,[20] maintains the legality of unilateral or collective humanitarian intervention, whether sanctioned by the UN Security Council or not.[21]  This view interprets Article 2(4) to allow use of force that is not “inconsistent with the Purposes of the United Nations.”[22] These purposes are reflected in the preamble of the Charter:



to reaffirm faith in fundamental human rights, in the dignity and worth of the human person…, AND FOR THESE ENDS… to unite our strength to maintain international peace and security, and to ensure… that armed force shall not be used, save in the common interest….”[23]


     The other camp, UN Charter strict constructionists, as represented by Professor Ian Brownlie, oppose any humanitarian intervention, unless through an appropriate organ of the United Nations or by peaceful invitation.[24]  The strict constructionists view humanitarian intervention as both a violation of the Charter[25] and as “wide open to abuse”[26] by “vigilantes and opportunists to resort to hegemonial intervention.”[27]


     Many, such as Brownlie, maintain that the sole Jus ad Bellum for modern times is use of force under the UN Charter.[28]  This ignores the reality of post-Charter history.  The UN Charter’s scheme to outlaw aggression remains an aspirational regime so long as the Security Council fails to take non-vetoed or consensus action.[29]  In the Charter’s vacuum between defined actions of self defense and aggression, lies the basis for most conflict since the Charter’s inception.  States justify their actions based on self-defense while protesting States maintain the action failed to meet the criteria justifying self-defense.[30]  Such argument and counter-argument characterizes the cold-war era of the Security Council’s history and explains the comparative inaction.


     Both camps seem to agree on one aspect of humanitarian intervention: UN Security Council sanctioned force to maintain international peace and security when human rights violations threaten that peace and security.  Consensus-based action, sanctioned by the Security Council may lawfully and unquestionably be taken to restore fundamental human rights.  Where consensus is lacking, nations must resort to the cold-war era practice of justifying intervention on customary international law and treaty obligations outside the Charter.[31] 


     Human rights law lists many specific rights founded in both customary and treaty law.  Conventional law sources include the UN Charter[32] and the Universal Declaration on Human Rights.[33]  However, not all human rights are peremptory norms (jus cogens).  So which human rights trigger coercive intervention when violated?  One American court answers:


the standards of human rights that have been generally accepted –and hence incorporated into the law of nations—are still limited.  They encompass only such basic rights as the right not to be murdered, tortured or otherwise subjected to cruel, inhuman or degrading punishment; the right not to be a slave; and the right not to be arbitrarily detained.[34]  



To that list one should add the rights to not be subjected to genocide, nor systematic racial discrimination.[35]  Those six fundamental rights are jus cogens.[36]  Violation of any of those or a consistent pattern of gross violations of internationally recognized human rights justifies humanitarian intervention.[37]


B. Security Council Coercion or Self-Defense—Use of Force and the UN Charter


     The UN Charter’s two main precepts related to use of force are: first, the concept of pacific settlement of disputes, which bans aggression; and second, the idea of coercive maintenance of peace and security.  Article 2(3) mandates pacific settlement of disputes: “All Members shall settle their international disputes by peaceful means in such a manner that international peace and security, and justice, are not endangered.”[38]  Article 2(4) outlaws aggression: “All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.”[39]


     The second precept, coercive or forceful maintenance of peace and security, exists as an exception to the first precept, peaceful settlement of disputes.  The Charter allows either

UN Security Council to sanction force,[40] or self-defense on an individual or collective basis.[41]


     The Charter implements these concepts for maintenance of international peace and security through Security Council action or, in the alternative, through independent action in self-defense.  First, the Charter prefers Security Council action to restore peace or to maintain security.  Security Council powers to respond to aggression reside in Articles 24-26 and Chapters VI, VII, VIII and XII.  The Security Council’s right to a coercive response to aggression and other threats to international peace and security exists in Article 42 of Chapter VII.  The Security Council may authorize “action by air, sea, or land forces as may be necessary to maintain or restore international peace and security.”[42] 


     Should the Security Council not respond to aggression, by failure or inaction, then regional arrangements or agencies are encouraged to take action.  Article 51 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 Council has taken measures necessary to maintain international peace and security.”[43]   Additionally, Articles 52 through 54 provide for regional arrangements to maintain peace and security.  Finally, self-help by individual states may occur to defend against aggression.  The UN Charter does not abrogate the inherent right of self-defense.[44] Individual or collective self-defense may continue until the Security Council acts.


III.  Jus ad Bellum for Contemporary Military Operations


      How do these legal theories support aerospace intervention, such as no-fly zones?  These operations may be legitimately conducted under any of the following justifications: one, when sanctioned by the UN Security Council;[45] two, when founded on customary humanitarian intervention law;[46] or three, in exercise of inherent individual or collective self-defense to deter aggression.[47] In other words, US leadership may operationally engage the US Air Force on the basis of humanitarian intervention and claim legitimacy[48] to such aerospace intervention, provided the legal criteria exist.  For US military operations other than war, “legitimacy is a condition based on the perception by a specific audience of the legality, morality, or rightness of a set of actions.  This audience may be the US public, foreign nations, the populations in the area of responsibility…, or the participating forces.”[49]     


     Scholars assert various criteria to justify humanitarian intervention operations on both moral[50] and legal[51] grounds.  Common to these views are: the requirements of a breach of a ‘fundamental’ human right; a necessity brought on by failure to peacefully resolve the breach; and a proportionate response, ending as soon as the breach and its threat to international peace and security is resolved. American military action taken in Somalia, Iraq, Haiti, the Balkans, and Rwanda were based, to some greater or lesser degree, on humanitarian principles.  We now have a history of humanitarian intervention along with a history of military peace making, peace keeping, peace enforcement operations.  Aerospace intervention, particularly no-fly zones, presents an option of first choice and remains an integral component of any humanitarian operation where the target-state opposes the intervention or conflict remains a possibility. 

1 CHARTER OF THE UNITED NATIONS, 59 Stat. 1031, T.S. 993, 3 Bevans 1153 (signed at San Francisco on 26 June, 1945; entered into force on October 24, 1945) [hereinafter, The Charter or UN Charter].


2 See W. Hays Parks, Air War and the Law of War, 32 A.F. L. REV. 1, at 4 (“Jus ad bellum is a Latin term meaning ‘up to the commencement of war.’  Basically, the proper circumstances to resort to force or war.” Id. at note 14); MORRIS GREENSPAN, THE  MODERN LAW OF LAND WARFARE 41 (1959) (describing the concept as “the doctrine of bellum justum, just war,” quoting Kelsen.  Id. at note 25).  See also MICHAEL WALZER, JUST AND UNJUST WARS (1977); YEHUDA MELZER, CONCEPTS OF JUST WAR (1975); RICHARD A. FALK, LAW, MORALITY, AND WAR IN THE CONTEMPORARY WORLD (1963).  I basically interpret jus ad bellum to mean: the right reasons to resort to war; just recourse to war; the combined moral and legal justifications for going to war; or simply, the reason a nation fights a war or places her armed forces into potential combat.


[3] Francis Lieber, quoted by Telford Taylor, War Crimes, in WAR, MORALITY, AND THE MILITARY PROFESSION 378 (Malham M. Wakin ed., 1986)[hereinafter, WAR, MORALITY, AND THE MILITARY].

[4] See Parks, supra note 2, at 4.


[5] WAR, MORALITY, AND THE MILITARY, supra note 3, at 220.  See, Major Michael N. Schmitt, The Confluence of Law and Morality: Thoughts on Just War, 3 USAFA J. LGL. STUDIES 91-106 (1992)(Schmitt provides a full explanation of Just War theory as developed by the Catholic Bishops.  He states, “there are nine just war requirements, seven relating to the issue of resort to force, jus ad bellum, the final two to the methods of employing it, jus in bello.  Each not only reflects the evolution of the doctrine, but is also evident to varying degrees in the modern law of armed conflict.” Id. at 94.  The nine just war requirements are: (1) just cause;

(2) competent authority; (3) comparative justice; (4) right intention; (5) last resort; (6) probability of success; (7) jus ad bellum proportionality (of the resort to war—balancing the harm caused by war against the values sought to be protected);  (8) jus in bello proportionality (in the waging of war—balancing the battle method or means against the military advantage gained; and (9) discrimination (distinguishing between valid military targets and those immune from combat: civilian non-combatants, those hors de combat, such as prisoners of war, or the wounded and shipwrecked at sea).


[6] George Weigel, Low Intensity Conflict in the Post-Cold War World: The American Moral-Cultural Environment, in HUMANITARIAN INTERVENTION AND THE UNITED NATIONS 257 (Richard B. Lillich ed. 1973).


[7] WAR, MORALITY, AND THE MILITARY, supra note 3, at 220.


[8] See A. P. V. ROGERS, LAW ON THE BATTLEFIELD 3-7 (1996).


[9] Taylor, in WAR, MORALITY, AND THE MILITARY supra note 3, at 377-78.


[10] Jennings, The Caroline and McLeod Cases, 32 AM. J. INT’L. L. 82 (1938).


[11] Letter to British Envoy Fox, April 24, 1841, 29 BRIT. & FOREIGN ST. PAPERS, 1840-1841, at 1129, 1138 (1857)(Secretary Webster’s letter goes on to require the British to show that even assuming necessity, that they “did nothing unreasonable or excessive, since the act, justified by the necessity of self-defense, must be limited by that necessity and kept clearly within it.” Id.)


[12] See Lt Col Richard J. Erickson, Use of Armed Force Abroad: An International Law Checklist, VOL. 15 NO. 2 THE REPORTER 3-8 (AF JAG School ed.,198_)(Erickson provides thirteen legal justifications for use of force and rates their acceptability in the world community and the conditions required to satisfy each basis for use of force.  The justifications given are: (1) national self-defense; (2) anticipatory self-defense; (3) collective self-defense;     (4) collective anticipatory self-defense; (5) regional arrangement enforcement action; (6) regional peacekeeping; (7) invitation; (8) peacetime reprisal; (9) protection of state’s nationals; (10) humanitarian intervention; (11) hot pursuit; (12) suppression of piracy; and (13) self-help.  Id.).


[13]“Traditionally, states have been free under international law to treat their nationals as they wish.” R. SWIFT, INTERNATIONAL LAW: CURRENT AND CLASSIC 324 (1969).


[14] An American federal court viewed this principle as follows:


International law, as its name suggests, deals with the relations between sovereign states, not between states and individuals.  Nations not individuals have been its traditional subjects. 

…  As long as a nation injures only its own nationals, however, then no other state’s interest is involved; the injury is a domestic affair, to be resolved within the confines of the nation itself.


     Recently, this traditional dichotomy between injuries to states and to individuals –and between injuries to home-grown (sic) and to alien individuals—has begun to erode.  The international human rights movement is premised on the belief that international law sets a minimum standard not only for the treatment of aliens but also for the treatment of human beings generally. 


De Sanchez v. Banco Central de Nicaragua, 770 F.2d 1385, 1396-97 (5th Cir. 1985)[hereinafter, De Sanchez opinion] (citations omitted).


[15] According to Professor Greenspan:


“There have been numerous cases during the nineteenth and twentieth centuries where the shocking treatment by a state of its own subjects moved other states to intervene on ‘grounds of humanity,’ as for instance, in the massacre of Christians in Armenia and Crete under the Ottoman empire, in 1891-1896, and further massacre of the Armenians in 1915, and the persecution and massacre of the Jews under tsarist Russia, 1882 and 1903.” 


GREENSPAN, supra note 2, at 438 (citations omitted).


[16] W. Michael Reisman, Humanitarian Intervention to Protect the Ibos, reprinted in HUMANITARIAN INTERVENTION AND THE UNITED NATIONS at 168-171. (Richard B. Lillich ed. 1973).


[17] Id. at 170.


[18] Report of the Sub-committee of the League of nations Committee of Experts for the Progressive Codification of International Law on Responsibility of States for Damage Done in Their Territories to the Person or Property of Foreigners, 20 AM. J. INT’L. L., Special Supp. 177, 182 (1926), cited in A. THOMAS & A. THOMAS, THE DOMINICAN REPUBLIC CRISIS 1965 (J. Carey ed. Hammarskjold Forum 1967), quoted in Reisman, Id. at 168 note 2, 170 note 17.


[19] See Jean-Pierre L. Fonteyne, Forcible Self-Help by States to Protect Human Rights: recent Views from the United Nations, in HUMANITARIAN INTERVENTION AND THE UNITED NATIONS 197-221(Richard B. Lillich ed. 1973)(providing a balanced overview of many leading positions for and against humanitarian intervention).


[20] See Schmitt, supra note 5, at 91-106 (explaining that the New Haven school of international law is ‘policy-oriented.’ “Its proponents view international law as ‘an ongoing process of decision through which the members of the world community identify, clarify, and secure their common interests.” Id. at 92).


[21]   Reisman, supra note 16, at 167-195.


[22] U.N. CHARTER, art. 2, para. 4.


[23] U.N. CHARTER, preamble, para. 1 and para. 2.


[24] Ian Brownlie, Thoughts on Kind-Hearted Gunmen, reprinted in HUMANITARIAN INTERVENTION AND THE UNITED NATIONS 139-148 (Richard B. Lillich ed. 1973).


[25] Id. at 142-143.  See also Louis Henkin, Use of Force: Law and U.S. Policy, in RIGHT V. MIGHT: INTERNATIONAL LAW AND THE USE OF FORCE 37 (1959) (arguing “Extravagant claims of right to act in self-defense have been the principle threat to the law of the Charter.”);  but see John Norton Moore, Low Intensity Conflict and the International Legal System, in LEGAL AND MORAL CONSTRAINTS ON LOW-INTENSITY CONFLICT 25 (67 U.S. Naval War College International Law Studies, Alberto R. Coll et al. eds., 1995) (also quoting Henkin and challenging him directly: “These ‘principal threats’ to the Charter did not result from an expansion of the right of defense but rather because of a willingness by aggressive totalitarian regimes to commit aggression and a system perceived by them as unlikely to provide effective defense.” Id. at 31).


[26] Brownlie, supra note 24, at 146.


[27] Id. at 148.


[28] See Henkin, supra note 25; A. THOMAS & A. THOMAS, supra note 148; IAN BROWNLIE, INTERNATIONAL LAW AND THE USE OF FORCE BY STATES (1963).


[29] Major Michael Schmitt, The Resort to force in International Law: Reflections on Positivist and Contextual Approaches, 37 A.F. L. REV. 105, at 110-112 (stating Article 2(4) and the ensuing “positivist system envisioned in the Unite (sic) Nations Charter was for all practical purposes stillborn.” Id. at 110).  See also Robert F. Turner, State Sovereignty, International Law, and the Use of Force in Countering Low-Intensity Aggression in the Modern World, in LEGAL AND MORAL CONSTRAINTS ON LOW-INTENSITY CONFLICT 81 (67 U.S. Naval War College International Law Studies, Alberto R. Coll et al. eds., 1995) (Professor Turner comments: “The 1990-91 Gulf crisis provided hope that the essentially stillborn U.N. Security Council might be rejuvenated and permitted to play a central role in peacekeeping.” Id.).



[30] Oscar Schachter, Self-Defense and the Rule of Law, 83 AM. J. INT’L. L. 259-277 (1989).


[31] See RESTATEMENT (THIRD) OF THE FOREIGN RELATIONS LAW OF THE UNITED STATES [hereinafter, RESTATEMENT (THIRD)] Sec. 703 and accompanying commentary and reporter’s notes (1986).


[32] Supra note 1.


[33] International Declaration of Human Rights, adopted 10 Dec., 1948, 3 G.A. Res. 217, U.N. Doc. A/180 at 71 (1948).


[34] De Sanchez opinion, supra note 10, at 1397.


[35] RESTATEMENT (THIRD) supra note 31, at Sec. 702, comments and reporter’s notes thereafter.


[36] Id. at comments m and n.


[37] Id. at Sec. 703 comment e, and Sec. 905.


[38] U.N. CHARTER, art. 2, para 3.


[39] U.N. CHARTER, art. 2, para 4.


[40] U.N. CHARTER, art. 42.


[41] U.N. CHARTER, art. 51.


[42] U.N. CHARTER, art. 42.


[43] U.N. CHARTER, art. 51.


[44] See generally Schachter, supra note 30 (Professor Schachter explores “aspects of the problem raised by … challenges to the applicability of international law to claims of self-defense.” Id. at 259).


[45] RESTATEMENT (THIRD) supra note 31, at Sec. 703, comment e:


It is increasingly accepted that a state may take steps to rescue victims or potential victims in an action strictly limited to that purpose and not likely to involve disproportionate destruction of life or property in the state where the rescue takes place.  …  Such intervention might be acceptable if taken pursuant to resolution of a United Nations body…. 


[46] RESTATEMENT (THIRD) supra note 31, at Sec. 702 and comments thereto.


[47] See Moore, supra note 25 (Professor Moore maintains “I believe that, in reality, when faced with an ongoing pattern of aggressive attack, it is certainly within the right of individual and collective defense to take necessary and proportional actions to effectively end the attack….  This right of defense is classic international law, not the fashionable contemporary inversion of this principle.”  Id. at 36).


[48] American military doctrine considers legitimacy as a principle of military operations other than war.  THE JOINT CHIEFS OF STAFF, JOINT PUB 3-07: JOINT DOCTRINE FOR MILITARY OPERATIONS OTHER THAN WAR (1995) [hereinafter, JOINT PUB 3-07] at II-5; U.S. DEP’T OF ARMY, FIELD MANUAL 100-5, OPERATIONS, at 13-3 to 13-4 (June 1993).


[49] JOINT PUB 3-07, id. at II-5.  The manual also notes that US public perceptions of legitimacy are “strengthened if there are obvious national or humanitarian interests at stake, and if there is assurance that American lives are not being needlessly or carelessly risked.”  Id.


[50] See Fernando R. Teson, Low-Intensity Conflict and State Sovereignty: A Philosophical Analysis, in LEGAL AND MORAL CONSTRAINTS ON LOW-INTENSITY CONFLICT 87 (67 U.S. Naval War College International Law Studies, Alberto R. Coll et al. eds., 1995).  Teson maintains that coercive  operations other than war are morally justified on six conditions:


1)  The ends of the operation are morally justified goals under just war theory.  A war has a just aim when it is waged in the defense of persons and, derivatively, of just institutions


2)  The government contemplating the operation is a legitimate government.


3)  Either the target State or the target government are illegitimate.


4)  The operation does not otherwise violate human rights.


5)  The operation is necessary and proportionate.


6)  The modus operandi is not such that would undermine the flourishing of civic and personal virtues that a liberal democracy must encourage.


Id. at 89.


[51] See Turner, note 29 at 79-80.  Professor Turner would permit military force or the threat of such force to be used under the following five guidelines:


(1)  There must be a breach of State responsibility on the part of the State against whose territory the use of force is being contemplated, …and,


(2)  Peaceful means of resolving the dispute must have been exhausted (or it must be clear that they would not succeed);  and,


(3)  The level of force used must be limited to that necessary to bring an end to the unlawful threat to the State; and,


(4)  Reasonable efforts must be taken to avoid any unnecessary interference in the internal affairs of other States; and,


(5)  Consistent with (4), all intervention in the second State must be brought to an end at the earliest possible date.


Id. at 79-80.  See also John M. Collins, Military Intervention: A Checklist of Key Considerations, VOL. XXV, NO. 4 PARAMETERS 53 (Winter 1995-96)(Mr. Collins presents eight separate checklists for American leadership to check their premises for entering into expeditionary operations).