ndupress.ndu.edu SF No. 286 1 

The struggle against terrorism—more specifically, the effort to prevent 

terrorist attacks—has raised difficult legal and policy issues including 

so-called targeted killing, or the killing of specific individuals because 

of their involvement in terrorist organizations and operations. As we shall see, 

this form of targeted killing involves domestic and international legal authorities 

and policy and prudential issues. A substantial number of countries confronting 

what they consider to be terrorist attacks and threats engage in targeted killings. 

Each has to resolve questions about authorities and prudence because, while 

terrorists are always criminals, they also may be lawful military targets. The dual 

character of terrorists leads to the conclusion that, as a matter of policy, a state 

should weigh the totality of the circumstances and conclude that no other action 

is reasonable to prevent a terrorist attack before engaging in the targeted killing. 

Careful analysis in advance may preempt problems later.

This essay addresses the question principally from the American perspective. It examines the authority, as a matter of U.S. law, for the United States 

to kill individual terrorists and the international legal context for such operations. The operating premise is that the targeted killing of al Qaeda leaders is 

emblematic of the subject under review in contrast to such domestic police 

action against terrorists as the arrest, prosecution, conviction, and execution 

of Timothy McVeigh, who was principally responsible for the bombing of the 

Federal office building in Oklahoma City in April 1995.1

 The essay concludes 

that authority in domestic and international law exists for such operations 

and that, as a policy choice, the United States would do well to apply the Geneva Conventions of 1949 in the conflict with terrorists whether or not it is 

legally required. In any event, policymakers need to weigh the consequences 

of targeted killing operations because, like all military operations, unforeseen 

results—positive and negative—are likely. 

Targeted Killing of Terrorists

By Nicholas Rostow

Strategic Forum

National Defense University

About the Author

Dr. Nicholas Rostow is Distinguished 

Research Professor and Senior 

Director in the Center for Strategic 

Research, Institute for National 

Strategic Studies, at the National 

Defense University. He is also a Senior 

Research Scholar at the Yale Law 

School.

Key Points

◆◆ The battle against terrorism 

raises important legal and policy 

concerns for the United States. 

Efforts to prevent terrorist attacks 

include the controversial practice 

of targeted killing, for example—

the identification and killing of 

individuals involved in terrorist 

operations and organizations.

◆◆ Authority for targeted killing exists 

in domestic and international law. 

◆◆ As a matter of policy even if it is 

not legally required, the United 

States should use the Geneva 

Conventions of 1949 to guide its 

confrontations with terrorists.

March 2014

Center fo

r Strategic R

eSEARCH
2 SF No. 286 ndupress.ndu.edu

Authorities for Targeted Killing

As spokesmen for the U.S. Government have emphasized,2

 America’s use of force against terrorists takes place 

in the context of “armed conflict.” For practical and legal 

reasons they distinguish the conflict with al Qaeda and 

similar organizations from counterterrorism law enforcement at home or in other countries, which principally involves the police. This delimitation is commonsensical. It 

is also is important. One does not want the U.S. Government engaging in military operations on American soil 

absent extraordinary circumstances. Authority for using 

the military instrument abroad against terrorists in the 

context of “armed conflict” comes from the Constitution 

and statute, and the use of armed force needs to comply 

with the international law of armed conflict (also known 

as the laws of war or international humanitarian law).

More than 200 years of practice have confirmed 

that the President has the responsibility to direct the 

Armed Forces to defend the country. The President accordingly had constitutional authority to order counterattacks by U.S. forces against terrorists who had 

engaged in attacks against the United States and its 

citizens even before September 11, 2001.

Presidents George W. Bush and Barack Obama have 

not had to rely on their constitutional authority alone. After September 11, 2001, Congress gave the President broad 

authority “to use all necessary and appropriate force against 

those nations, organizations, or persons he determines 

planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored 

such organizations or persons, in order to prevent any future 

acts of international terrorism against the United States by 

such nations, organizations, or persons.”3

 This statute provided explicit authority for U.S. military operations in Afghanistan and against those the President determined were 

involved in the September 11 attacks. The words “necessary 

and appropriate” limit the use of the military instrument to 

those situations where police action, by the United States 

or the state in which the terrorist is found, is impossible. 

Had the perpetrators resembled Timothy McVeigh and 

been subject to arrest inside the United States, the use of the 

Armed Forces would have been neither necessary nor appropriate. One therefore should not expect drone attacks in 

London. In states unable or unwilling to take action to prevent their territories from being used by terrorists, the legal 

and practical situation is different. A use of force, as against 

Osama bin Laden, may be lawful as well as the only practicable course, especially when a host government withholds 

its cooperation. On balance, it became more important to 

the United States and to the international multilateral effort to suppress terrorism to capture or kill bin Laden than 

to be sensitive to a breach of Pakistan’s territorial integrity 

and amour propre. 

The conduct of military operations pursuant to these 

constitutional and statutory authorities has to conform 

to U.S. legal obligations regarding armed conflict. In the 

main, the rules for American use of force are contained in 

the Geneva Conventions of 1949 and subsequent treaties 

to which the Nation is a party or, as in the case of some 

articles of the 1977 Protocols Additional to the 1949 Geneva Conventions, which Washington regards as accurate 

statements of the customary international law of armed 

conflict. In 2010 the State Department Legal Adviser 

stated that the United States applied “law of war principles,” including:

First, the principle of distinction, which requires 

that attacks be limited to military objectives and 

that civilians or civilian objects shall not be the 

subject of the attack; and

Second, the principle of proportionality, which 

prohibits attacks that may be expected to cause 

incidental loss of civilian life, injury to civilians, 

damage to civilian objects, or a combination thereof, 

that would be excessive in relation to the concrete 

and direct military advantage anticipated.4

In other words, if the target is lawful under the laws of 

armed conflict, a state may use weapons, including weapons delivered by remotely piloted, unmanned aerial vehicles, against such targets. In this sense, targeted killing is 

high technology sniping.
ndupress.ndu.edu SF No. 286 3 

This analysis rests on the premise that the United States 

is in an armed conflict with al Qaeda as a result of the attacks of September 11, 2001, a conclusion that itself reflects 

a process of analysis. Under longstanding principles of international law, a state bears responsibility for uses of force from 

its territory about which it knew or should have known. That 

responsibility includes a duty to prevent and, if prevention 

proves impossible, suppress. When a state is unable or unwilling to discharge such international legal obligations, the 

victim state presumptively has rights of self-defense. Thus, 

when Afghanistan was the base from which the 9/11 attacks 

were conducted and when Afghanistan was unwilling or unable to take action against the perpetrators, the United States 

enjoyed the right to use force in self-defense to attack those 

actors in Afghanistan. This legal analysis provides the basis 

for the U.S. use of force in Afghanistan commencing in 2001.

Laws of War and Targeted Killing

Confusion has bedeviled discussion of the conflict 

between the United States and al Qaeda. Assuming that 

al Qaeda is a true nonstate actor, governments have had 

to decide whether the United States is in international 

armed conflict with al Qaeda and, if so, what rules apply. 

These questions are rooted in the language of the four 

Geneva Conventions of 1949. 

By their terms, the Conventions apply to conflicts among 

the “High Contracting Parties” or to “armed conflict[s] not of 

an international character occurring in the territory of one 

of the High Contracting Parties.”5 This language means, respectively, conflicts between or among states and civil wars.6

Based on that language, the U.S. Supreme Court determined 

that the conflict with al Qaeda was a global, noninternational 

armed conflict to which Common Article 3 of the Geneva 

Conventions of 1949 applied because that seemed to be the 

only part of the Conventions that could apply to nonstate actors.7

 While the effort to avoid placing alleged terrorists in a 

legal no-man’s-land is laudable, the Supreme Court’s effort in 

this regard involved intellectual incoherence. As it must, the 

executive branch adheres to the Supreme Court decision. At 

the same time, without violating that decision, the U.S. Government may follow an intellectually coherent and simpler 

approach than the Supreme Court’s by following the Geneva 

Convention lead.8

The Geneva Convention Approach 

The Geneva Conventions, binding as they are on all 

states, provide a useful guide to governments. They do so 

whether one uses military or law enforcement instruments 

against terrorists. If a government treats terrorists outside 

its jurisdiction or the jurisdiction of a state capable of using 

the criminal law against terrorists as subject to the Geneva 

Conventions, then its course is clear. If it captures a terrorist 

fighter, that fighter may be prosecuted for violations of the 

Geneva Conventions and then returned to prisoner of war 

status once a sentence, if any, is served. Prisoner of war status 

ends with the end of the conflict. Today it is difficult to foresee an end to the U.S. conflict with al Qaeda notwithstanding the deaths of so many al Qaeda leaders and followers.

Treating terrorists as if they are not combatants and are 

not entitled to prisoner of war status may be legally correct; 

it nonetheless puts a government in a policy and legal straitjacket. Terrorists inevitably fail the requirements set forth 

in the third Geneva Convention to wear a uniform, carry 

weapons openly, obey the laws of war, and operate in an 

organized fashion under a commander responsible for his 

or her subordinates, with rigorous systems of command and 

control, in order to enjoy the privileged status of combatant 

and prisoner of war upon capture.9 The terrorists’ failure in 

these respects does not make it easier to deal with detainees, as the American experience during the past 11 years 

demonstrates. As a result, a new approach is needed. That 

approach should be rooted in the law and in common sense. 

The Geneva Conventions provide both.

For the United States, acting as if terrorists captured in 

battlefield conditions are combatants and therefore prisoners of war would have a number of benefits. First, it would 

limit challenges to the legal status of detainees because they 

would not be held in what might appear to be legal limbo. 

As a result, whether they were held in prisoner of war facilities within the United States or at Guantánamo Bay would 

not matter in legal terms. Detainees would not acquire more 

rights by being held as a prisoner of war within the United 
4 SF No. 286 ndupress.ndu.edu

States than they do in Guantánamo Bay, and the administration should be able to close the prison facilities there 

without increasing its legal exposure. Second, it would clarify the status of prisoners for prison guards by making clear 

that the prisoners were not in a penitentiary status unless 

convicted of a crime. Third, it could improve the international reputation of the United States, which stands sullied 

as a result of allegations of torture and questions about its 

authority to hold alleged terrorists indefinitely, even those 

who might be acquitted at trial. 

Conclusion

Since 9/11, the United States has traveled far in its 

quest to diminish, if not eliminate, the risk of terrorist attack. 

In the process it has revealed much about its willingness 

to engage in targeted killing and the conclusion that this 

tactic is useful and “wise” as well as legal.10 The argument 

for wisdom is that technology permits such a high degree 

of accuracy that collateral damage—the killing of bystanders—and the risk to American lives are reduced. The third 

test of wisdom is an act’s consequences. The wise strategist 

will weigh consequences of chosen tactics. For example, the 

negative consequences of the frequent U.S. use of remotely 

piloted aircraft—drones—to attack al Qaeda in Pakistan in 

2011 led to an intense “Pakistani animus toward unilateral 

U.S. action [with] huge implications for America’s counterterrorism aspirations in the country.”11 To avoid negative 

consequences does not require inaction, but rather an effort 

at forethought and foresight. It is something that cannot be 

guaranteed even if one abides by the law. So far the United 

States has followed U.S. and international law by engaging 

in targeted killing as a combat tactic against military targets. 

Keeping to this line will be clarifying and simplifying even 

though one may argue that the law does not require treating 

terrorists as if they were military targets. Lawfulness by itself 

does not guarantee wisdom. But it is a good starting place. 

Notes * Courtney Lang, class of 2015 at the Georgetown University 

School of Foreign Service, ably assisted in the preparation of this 

essay for publication.

1 See generally, Nicholas Rostow, “The Laws of War and the 

Killing of Suspected Terrorists: False Starts, Rabbit Holes, and Dead 

Ends,” Rutgers Law Review 63, no. 4, Summer 2011, 1215.

2 See Harold Hongju Koh, “The Obama Administration and 

International Law,” Annual Meeting of the American Society of International Law, Washington, DC, March 25, 2010; Eric Holder, Remarks 

at the Northwestern University School of Law, March 5, 2012. 

3 Joint Resolution, “Authorization for Use of Military Force,” 

September 18, 2001, P.L. 107-40 [S.J. Res. 23].

4 Koh. 

5 Common Article 3 to the Four Geneva Conventions of August 

12, 1949, reprinted in Documents on the Laws of War, ed. Adam Roberts and Richard Guelff, 245 (New York: Oxford University Press, 3rd

edition, 2000).

6 Rostow, 1231 (relying on Dinstein).

7 Hamdan v. Rumsfeld, 548 U.S. 557, 630 (2006).

8 See Rostow, 1231–1232.

9 Geneva Convention Relative to the Treatment of Prisoners 

of War, August 12, 1949, in Documents on the Laws of War, 246 (Art. 

4A(2)).

10 Compare Chris Toensing and Ian Urbina, “Israel, the US and 

‘Targeted Killings,’” Middle East Report Online, Middle East Research 

and Information Project, February 17, 2003, to John O. Brennan, 

transcript, “The Ethics and Efficacy of the President’s Counterterrorism Strategy,” Woodrow Wilson International Center for Scholars, 

April 30, 2012. 

11 Thomas F. Lynch III, The 80 Percent Solution: The Strategic Defeat 

of bin Laden’s al-Qaeda and Implications for South Asian Security, National 

Security Studies Program Policy Paper (Washington, DC: New 

America Foundation, February 2012), 15.

The Center for Strategic Research within the Institute for 

National Strategic Studies provides advice to the Secretary of Defense, Chairman of the Joint Chiefs of Staff, and 

unified combatant commands through studies, reports, 

briefings, and memoranda. The center conducts directed 

research and analysis in the areas of strategic and regional studies and engages in independent and leading-edge 

research and analysis in related areas.

The Strategic Forum series presents original research by 

members of NDU as well as other scholars and specialists in national security affairs from the United States and 

abroad. The opinions, conclusions, and recommendations 

expressed or implied within are those of the contributors 

and do not necessarily reflect the views of the Defense 

Department or any other agency of the Federal Government. Visit NDU Press online at ndupress.ndu.edu.

Nicholas Rostow

Director

Center for Strategic Research

William T. Eliason

Director

NDU Press

Institute for National Strategic Studies

R.D. Hooker, Jr.

Director for Research

and Strategic Support