In trying to analyze the legal implications of the events of September 11, international lawyers and government officials are finding themselves in somewhat uncharted territory. Because the attacks on the Pentagon and the World Trade Center complex were apparently carried out by non-state actors who may have planned, organized, and financed key aspects of their illicit activities in other states, it is not easy to frame U.S. responses within familiar categories recognized by international law. Normally, a state goes to war against another state or internal enemies. Although the war that the U.S. has pledged to wage against the perpetrators of these horrific acts and the state(s) that harbor them does not fit neatly within existing paradigms, any ensuing hostilities will nonetheless be based on or extrapolated from preexisting international law rules and principles.

In analyzing these events, it is important to distinguish two separate, but interrelated branches of international law: the law governing the resort to armed force and the law applicable to the conduct of hostilities. The former is found in the UN Charter and state practice and the latter in the law of armed conflict, also known as International Humanitarian Law (IHL).

Historically, states recognized a right to resort to war as a lawful means to settle political disputes with other nations. Hostilities were frequently triggered by formal declarations of war or armed attacks followed by such a declaration or by other acts indicating an intention to engage in warfare. With the adoption of the UN Charter in the wake of World War II, the legal rules changed in this regard. By signing the UN Charter, states renounced the use of force as a means of settling disputes and effectively outlawed aggressive war.¹ The states did not however, relinquish the right to self-defense. Article 51 of the Charter recognizes that a state which is the victim of an armed attack (presumably by another state (or states) can lawfully resort to force in exercise of the inherent right of individual or collective self-defense against aggression.

The term “war” has a particular meaning in U.S. law which involves complex constitutional issues of separation of powers. Under the federal constitution, only Congress can declare war and it has not done so since World War II. However, even without such a declaration, but under the President’s express and implied powers, the U.S. has been involved in numerous armed conflicts, including Korea, Vietnam, Kosovo, Grenada and Panama. Like his father, who was President during the Gulf war, George W. Bush has received from the Congress, not a declaration of war as such, but a Joint Resolution authorizing him to use military force against nations, organizations, and persons involved in these attacks and against those states which harbor terrorist organizations and persons. Various actions on the international level have significantly strengthened the President’s hand to undertake, consistent with international law, hostile acts against these persons, groups and/or states.

Certainly, if a state had launched these attacks, the U.S. could, under Article 51 of the UN Charter, legitimately take military action against that state and call on other states to assist it. Significantly, the NATO Treaty--which declares an attack on one member an attack on all members of the Alliance--has been invoked for the first time and may well result in unprecedented joint military operations under that treaty. A claim by NATO members that they are acting in accordance with Article 51 and the Charter’s purposes would carry great weight and contribute to the interpretation of Charter norms. It is extremely important that the day after the attacks, the Security Council voted unanimously to approve Resolution 1368 (2001), which states that any act of international terrorism is a threat to international peace and security. The Resolution calls on all states to bring to justice “the perpetrators, organizers and sponsors” of these terrorist acts, and stressed that “those responsible for aiding, supporting or harbouring them would be held accountable.” It also pointedly recognized the right to individual and collective self-defense under the Charter. This measure, while not expressly authorizing the use of force, is sufficiently broad that it will unquestionably be relied on by the U.S. if it decides to employ force against any or all of these parties.

Can the U.S. be at “war” and engage in hostilities against non-state actors? Historical precedents suggest that it can. In 1805, the U.S. sent an expeditionary force to Tripoli to destroy the Barbary Pirates. In 1916, the U.S. military was sent into Mexico to kill or capture Pancho Villa and his band after they attacked U.S. nationals in New Mexico. Moreover, IHL permits governments engaged in civil wars and lesser internal hostilities to lawfully attack members of dissident armed groups, as well as individual civilians who directly participate in the hostilities by assuming the role of combatants. It is important to note that all such persons are effectively non-state actors. One might anticipate that the U.S. (by analogy to interstate armed conflict rules) will treat bin Laden and his associates as members of a paramilitary organization whose members do not comply with the most basic rules and customs of warfare. As such, the U.S. could treat them as unprivileged combatants subject to direct attack and, if captured, not entitled to prisoner of war status. Accordingly, they would be liable for trial in a U.S. court. They could be punished for all hostile acts associated with the attacks on the Pentagon and the twin towers, and for any offenses under domestic and international law committed prior to capture.

Had a state launched these attacks, that state would clearly be responsible for having initiated an aggressive war in violation of the UN Charter. As I’ve said, it is unclear whether non-state actors can be charged and tried for this particular offense. However, if these attacks are treated as acts of war, they constitute serious violations of the laws and customs of war. In this regard, IHL prohibits launching attacks against the civilian population, individual civilians, and/or civilian objects. Moreover, in 1977, when the states ratified Protocols I & II of the Geneva Conventions, they barred from any armed conflict acts or threats of violence whose primary purpose is to terrorize the civilian population.

The World Trade Center complex was a civilian object dedicated to ordinary civilian purposes and inhabited by peaceable civilians. Thus, these buildings were immune from direct attack. Their deliberate destruction with the clear intent to kill or wound civilians within those structures constituted an illegal indiscriminate attack. Another clear and illicit purpose of the attack was to terrorize and attack the morale of the civilian population. So great was the intended and actual number of civilian deaths attending these attacks that they also might qualify as a crime against humanity. The attack against the Pentagon arguably was also illegal. Although the Pentagon does qualify under IHL as a military objective or lawful target of attack during an armed conflict, it was attacked by perfidious or treacherous means--a hijacked civilian jetliner.

Other international crimes, punishable under the laws of the U.S. and other nations, were committed by the perpetrators of these attacks and their confederates. The seizure and destruction of the jetliners violated the 1970 Hague anti-hijacking convention, as well as domestic code², which imposes criminal liability for willfully destroying an aircraft and assaulting its passengers and crew. The effect on the passengers of these hijacked planes might well amount to hostage taking in violation of the Convention against the Taking of Hostages and U.S. law, ³which contains a similar proscription. Most of these crimes are already within the subject matter jurisdiction of U.S. courts.

War crimes, crimes against humanity, hijacking, and hostage taking are international crimes of universal jurisdiction, making the perpetrators subject to criminal prosecution by other states. At present, there is no international court with jurisdiction to try the perpetrators and their accomplices. However, the Security Council, or a group of states (perhaps NATO members) could establish an ad hoc tribunal based on the Yugoslav and Rwanda models.

President Bush has stated that the U.S. will make no distinction between the perpetrators and those (presumably states) who harbor them. Can the U.S. invoke Article 51 of the UN Charter to justify taking military action against a state that did not perpetrate the attacks of September 11, but merely harbors the intellectual authors of and accomplices in these events? It is legally plausible that the U.S. and its allies might impute these acts of terrorism to such a state(s), thereby holding it responsible for these crimes. International law recognizes that the acts of non-state actors may be attributed to a state. The U.S. may argue that Afghanistan, for example, is guilty of both omission and commission in connection with these and previously realized or foiled attacks by bin Laden and his associates. That argument might posit that the Taliban’s failure to take action against bin Laden effectively amounts to a pattern of state tolerance of and acquiescence in these illicit acts sufficient to impute and thus attribute the conduct to the state itself. International human rights bodies have used such reasoning in finding states responsible for the conduct of non-state actors. For example, in 2000 the Inter-American Commission on Human Rights in the Massacre of Río Frío case found Colombia responsible for atrocities committed by the Autodefensas Unidas de Colombia, a paramilitary group. The Commission found that, even though the state had declared such groups to be illegal, it tolerated their presence and had acquiesced in their depredations and killings in the particular circumstances of this case.

If the United States takes military action against Afghanistan or any other state, it will be involved in an international armed conflict⁴. As such, the U.S., its allies, if any, and the target state will be legally bound to conduct hostilities in accordance with IHL, most particularly, the Geneva Conventions and the laws and customs of warfare contained in the Hague Regulations. Unlike U.N. law, modern IHL is not concerned with the legality of the resort to force. Rather, its fundamental rules are designed to regulate and restrain the conduct of hostilities. Foremost among these rules are those designed to ensure the immunity of the civilian population and civilian objects, such as houses, schools etc., from direct attack. Belligerents must at all times distinguish between civilian and military sites and direct their attacks solely against the latter. Moreover, military targets cannot be attacked with impunity. Belligerents must take the necessary precautions to avoid or at least minimize expected civilian casualties (“collateral damage”). In other words, the U.S. cannot fight terror with terror. Apart from being unlawful, attacks against civilians and their morale are totally counterproductive, and wasteful of military assets.

Can the U.S. directly target bin Laden without violating U.S. and international law? The answer is yes. Some have seen Executive Order 12333, which effectively renounces the use of assassination as an instrument of U.S. policy, as a prohibition applicable to the present situation. I disagree. The ostensible purpose of the order at the time of its adoption was to preclude the U.S. from killing, for example, the leader of a state with which the U.S was not at war. The Order also prohibits the willful killing of a private person for political purposes. During situations of armed conflict, the legal situation is different. Combatants may lawfully target and kill enemy combatants, as well as civilians who directly participate in the hostilities. As these persons are legitimate targets of attack, their deaths are treated as justifiable homicide for which the attacker incurs no liability under domestic or international law. Such killings do not constitute assassinations within the meaning of the Executive Order or IHL, nor would they violate, in principle, the prohibition against arbitrary deprivation of life in human rights law.

As previously noted, the U.S. is justified in treating bin Laden and the members of his organization as a paramilitary force which engages in the illegal use of force. Whether the terrorists are regarded as paramilitary or as civilians who have assumed a combatant role, they are, in the context of interstate hostilities, unprivileged combatants who are subject, individually and collectively, to direct attack. So long as they are not attacked in a “treacherous” manner⁵, killing them would be a lawful act of war.

Click here to view Robert Kogod Goldman's response on "Is this a new kind of war?"