Published On: Wed, Jan 30th, 2019

Assassination And Targeted Killing: A Timely Jurisprudential Brief

Louis René Beres

“The safety of the People Shall be the highest law.”
Cicero, De Legibus [On the Laws]

In preparing for his first Singapore summit with North Korean President Kim Jung Un, U.S. President Donald J. Trump famously indicated that dip-
lomatic success would require “attitude, not preparation.” Similar ideas have seemingly guided his conceptualizations on all critical matters of warfare and counterterrorism, both at the operational and jurisprudential levels. At times, he has made various remarks concerning assassination and targeting killing that have no recognizable origins in any pertinent strategic or legal norms.  Accord-ingly, the core purpose of the following essay is instructional: to offer the U.S. government and President Trump a timely and informed framework for relevant legal policy planning.

In the very best of all possible worlds, there would be no reason to lay out precise normative prescriptions concerning any conceivable forms of killing
in the interest of national security. But, quite plainly, this is not the best of all possible worlds. For the U.S. government, a more-or-less continuous support of assassinations and targeted killing as occasionally integral components of U.S. national security policy is plausible, even predictable.

Although regrettable, perhaps, even President Trump’s predecessor, President Barack Obama, resorted to several high-profile assassinations, including both the well-publicized killing of Osama Bin Laden, and—with considerably less intentional visibility—U.S. citizen Anwar al-Alwaki. In this case, the killing of al-Alwaki was intentionally less visible because it rendered a U.S. citizen subject to extra-judicial execution without any “due process of law.”

Are such assassinations and targeted killings illegal prima facie, in absolutely any form, or are they in fact sometimes lawful, perhaps even law-enforcing? Providing an informed and authoritative answer to such a starkly complex question could prove tangibly helpful to the U.S. government, and, as a consequential corollary, to the United States as a whole.

Applicable Law

To begin, Donald Trump and his counselors should soon formally inquire as to what, precisely, is applicable law? Here is the skeletal start to a prospectively suitable and comprehensive reply: assassination is prohibited by Executive Order 12333 of the United States (1981), which stipulates: “No person employed by or acting on behalf of the United States Government shall engage in, or conspire to engage in, assassination.”  Assassination is also prohibited because of its prior criminalization under recognizable international law; and, international law is included in the law of the United States, most expressly in Article 6 of the U.S. Constitution (the “Supremacy Clause”).

There are many sources that point to the inextricable convergence of national and international law. According to Article 6 of the Constitution, “All treaties made….under the authority of the United States shall be the supreme law of the land.” Although Article 6 refers exclusively to treaties, the U.S. Supreme Court has also extended the process of incorporation to other sources of international law. As this legal expansion means that all of the international rules against assassination are now plainly the law of the United States, any attempt to modify prohibitions against assassination would be in apparent violation of U.S. municipal or domestic law.

When two states are at war, assassination is normally treated by international law as a war crime.  According to Article 23(b) of the regulations annexed to Hague Convention IV (1907): “It is especially forbidden….to kill or wound treacherously individuals belonging to the hostile nation or army.”10 U.S. Army Field Manual 27-10 (1956), incorporates this prohibition, and unambiguously links Hague Article 23(b) to assassination. Hague Convention IV is a treaty of Assassination and Targeted Killing the United States and is therefore the “supreme law of the land” under Article 6.

When two nations are at peace, assassination is normally treated by international law as one or more of the following crimes: aggression; terrorism; or intervention. For example, the UN General Assembly Definition of Aggression (1974) criminalizes “the use of armed force by a State against the sovereignty, territorial integrity or political independence of another State.” The Convention on the Prevention and Punishment of Crimes against Internationally Protected Persons, a treaty against terrorism, criminalizes “the intentional commission of a murder, kidnapping or other attack” upon public officials.

As for the rule of nonintervention, which may be violated by assassination, it can be found at customary international law, in the UN Charter, the Charter of the Organization of American States, the Convention on Rights and Duties of States, and the Convention Concerning the Duties and Rights of States in the Event of Civil Strife. The United States is bound by all of these prohibitions. It is technically impossible for the Congress or the president to formally legal-ize any assassination. Should these prohibitions be disregarded, the responsible high officials would be subject, at least in principle, to prosecution under authoritative international law16 as “common enemies of mankind” by any
state that had claimed universal jurisdiction. U.S. law accepts and reinforces these particular global obligations. According to paragraph 498 of Field Manual 27-10, any person—whether a member of the armed forces or a civilian—who commits an act that constitutes a crime under international law is responsible for the crime and is liable to punishment.

Those who would ask for a broader right of assassination must also recall that the president of the United States has taken an oath required by Article 2, Section 1, and Clause 7 of the Constitution “to preserve, protect and defend the Constitution of the United States.” In view of Article 6 and the associated Supreme Court judgments, this signals that the president is sworn to uphold the international law prohibitions concerning assassination. Similarly, Article 2 Section 3 requires the president to “take care that the laws be faithfully executed,” a charge that extends to respect for the lives of public officials in other states.

On the basis of these recognizable expectations, any attempts to undermine the operative executive order dealing with assassination would be illegal. An executive order is inferior to prevailing federal statutes. But even if an authentic public law allowing assassination in certain instances were passed (a more-or-less inconceivable prospect, in light of essential secrecy requirements), it would be inferior, under the U.S. Constitution, to already-incorporated international law.

“Legal” Assassination

These arguments notwithstanding, there are certain instances where assassination may not represent a violation of international law. Indeed, there are circumstances in which assassination may be construed as authentically law-enforcing. But how can this be, in view of the authoritative and seemingly ironclad prohibitions just identified and discussed?

The answer lies in the principle of jus cogens, or “peremptory” norms of international law. According to Article 53 of the Vienna Convention on the
Law of Treaties, “A peremptory norm of general international law….is a norm accepted and recognized by the international community of States as a custom from which no derogation is permitted and which can be modified only by a subsequent norm of general international law having the same character.” Even a treaty must always be subordinate to peremptory expectations: “A treaty is void if, at the time of its conclusion, it conflicts with a peremptory norm of general international law.”

Among the most ancient and “sacred” of peremptory norms is Nullum crimen sine poena, or “No crime without a punishment.” Where crimes are especially egregious, as in the case of Nuremberg-category crimes—crimes of war, crimes against peace, and crimes against humanity—this expectation is overriding. It follows that where known perpetrators of such egregious crimes,
including certain crimes of terrorism, cannot be punished by “normal” judicial remedy (i.e., extradition and prosecution), the effective choice must be to leave these perpetrators unpunished, or to punish them extra-judicially.

Assassination—subject to the undimmed constraints of discrimination, proportionality, and military necessity—may be the least costly form of extra-judicial punishment. Moreover, where crimes are still ongoing, the permissibility of assassination could be even greater, as an additional peremptory norm would be supported by such an extraordinary remedy—that is, by the conspicuous obligation in our post-Nuremberg world legal order to protect human beings from all clear and terrible infringements of their irreducible and immutable rights.

We may consider a concrete historical example. After the first Gulf War, Saddam Hussein killed and displaced thousands of Kurds and Shiite Arabs within Iraq. Leaving tactical difficulties aside, the assassination of Saddam could have spared at least many of these innocent lives. Supporting the peremptory expectations of both punishment for crimes and regard for essential human rights, such extra-judicial execution would have been distinctly law-enforcing.

Looking back from the standpoint of today’s chaos in Syria, Yemen, Afghanistan, and Iraq—and several other parts of this frequently volatile region—it was arguably a greater violation of international law to leave Saddam’s rule intact until the next Gulf War (Operation Iraqi Freedom) than to assassinate him. Even though such action would have compromised another peremptory expectation properly known as “due process of law,” there are times when the lives of multiple endangered persons must be regarded as overriding.

When understood as tyrannicide, assassination has long been considered to be lawful. Classical support for such a particular form of assassination can be found in Aristotle’s Politics, Plutarch’s Lives, and Cicero’s De Officis. According to Cicero:

There can be no such thing as fellowship with tyrants. Nothing but bitter feud is possible: it is not repugnant to nature to despoil, if you
can, those whom it is a virtue to kill; nay, this pestilent and godless brood should be utterly banished from human society. For, as we amputate a limb in which the blood and the vital spirit have ceased to circulate, because it injures the rest of the body, so monsters, who under human guise, conceal the cruelty and ferocity of a wild beast, should be severed from the common body of humanity.

The eighteenth century Swiss scholar, Emmerich de Vattel in The Law of Nations recalls that “the essential object of civil society” is to “work in concert for the common good of all.” Hence, he proceeds to inquire:

Could the society make use of its authority to deliver irrevocably itself and all its members to the discretion of a cruel tyrant? Surely not, since
it would lose all rights of its own if it undertook to oppress any part of the citizens. When, therefore, it confers the supreme and absolute power of government without express reserve, there is necessarily an implied reserve that the sovereign will use that power for the welfare of the people, and not for their destruction. If he makes himself the scourge of the State, he disgraces himself; he becomes no better than a public enemy, against whom the Nation can and should defend itself. And, if he has carried his tyranny to the extreme, why should the life itself, of so cruel and faithless an enemy, be spared?

Where it is committed internationally, tyrannicide might, in certain instances, also be defended as permissible or even law-enforcing. Here the defense of assassination would derive from the overriding obligation to support the authoritative human rights regime in a decentralized or “Westphalian” system of international law. Although the reasonableness of such a defense might be based entirely on expectations of nullum crimen sine poena, it could be augmented where particularly egregious crimes are still underway. In these cases, transnational assassination would represent an expression of “humanitarian intervention,” or the “Responsibility to Protect.”

For assassination to be a law-enforcing expression of humanitarian intervention, a number of pertinent criteria would need to be satisfied. First, the assassination itself would have to be limited—to the greatest extent possible—to the authoritative persons within the offending state. Second, the assassination would have to conform to all of the settled rules of warfare as they concern discrimination, proportionality, and military necessity.  Third, the assassination would need to follow intelligence assessments that point “beyond a reasonable doubt” to ongoing and egregious human rights violations. Finally, the assassination would need to be founded upon carefully calculated judgments that it would in fact remedy the precipitating human rights violations, and that it would do substantially less tangible harm to civilian populations than would the alternative forms of humanitarian intervention.

These determinations could be exceedingly problematic and might, individually or collectively, be founded upon erroneous information or assump-
tions. Nevertheless, the only alternative to such problematic determinations in our decentralized system of international law is: (a) a general renunciation of humanitarian intervention or Responsibility to Protect (R2P) as a permissible remedy for major crimes; or (b) a general reliance upon broader uses of force as instruments of humanitarian intervention. Recognizing that (a) would assuredly produce legions of innocent human victims each year; and that (b) would represent a far costlier means of law enforcement, assassination should not simply be dismissed out of hand as a permissible and purposeful expression of humanitarian intervention.

The utilitarian view here is that human actions should be evaluated in light of their consequences, and that only this consequentialist approach will enable a national leader to deal with complex moral and legal issues in a rational, clear, and objective fashion. The principle of “utility,” which has its relevant origins in Jeremy Bentham’s Introduction to the Principles of Morals and Legislation, is “that principle which approves or disapproves of every action whatsoever, according to the tendency which it appears to have to augment or diminish the happiness of the party whose interest is in question….to promote or to oppose that happiness.” A good utility-based argument against those who would claim that assassination is impermissible because it arouses antipathy is Bentham’s statement against the principle of sympathy and antipathy which “approves or disapproves of certain actions, not on account of their tending to augment the happiness of the party whose interest is in question, but merely because a man finds himself disposed to approve or disapprove of them: holding up that approbation or disapprobation as a sufficient reason for itself, and disclaiming
the necessity of looking out for any extrinsic ground.”

In the final analysis, whether or not assassination or targeted killing can be construed as properly lawful or even law-enforcing derives from the per-
sistently Westphalian logic of international law, from the multiple sources of international law identified at Article of the Statute of the International Court of Justice, and from the frequently irreconcilable nature of competing peremptory norms. Were the world legal order more effectively centralized or the mechanisms of extradition and prosecution more reliable and well-developed, permissible resorts to assassination would likely be an oxymoron. But in the absence of a capable supranational authority and of a viable enforcement apparatus in the extant system, assassination may, however regrettably, have its limited and proper place.

The above arguments are strengthened by the underlying and all-important expectations of natural law, or expectations that are always peremptory, above the particular constraints of human lawmaking. For Blackstone, writing in the fourth book of his Commentaries, Of Public Wrongs, it was essential to transform “the eternal, immutable laws of good and evil” into a practical and operational code.38 As a starting point for understanding the common law, the Commentaies reveal that all international law, or what Blackstone calls the “law of nations,” is “deducible” from natural law and therefore binding upon each and every state. Thus, each state is called upon “to aid and enforce the law of nations, as part of the common law, by inflicting an adequate punishment upon offenses against that universal law.”

When Thomas Jefferson set to work on the Declaration of Independence, he drew freely upon Aristotle, Cicero, Grotius, Vattel, Pufendorf, Burlamaqui, and, especially, John Locke. Asserting the right of revolution whenever government infringes upon “certain unalienable rights,” the Declaration posits a natural order in a world whose laws are external to human will and which are discoverable through human reason.

The theory of natural law, which is found, inter alia, in the Declaration and the Bill of Rights, is based on clarity, self-evidence, and coherence. Its validity cannot be challenged by considerations of power politics. To ignore any assassination imperatives that might lie latent in these documentary foundations of the United States—in particular, as we may witness egregious international crimes—would be illogical and self-contradictory, as it would nullify the immutable and universal law of nature from which these documents derive meaning.

Therefore, we may see that U.S. responsibility to ensure punishment and protect human rights derives not only from the explicit expectations of international law, but also from the natural law foundations of U.S. municipal law. In the strictest sense, the natural law foundations of our municipal law are not a distinct alternative to international legal norms, but rather a distinct source of international law. According to Article 38(c) of the Statute of the International Court of Justice, international law stems in part from “the general principles of law recognized by civilized nations.”

This means nothing less than that the U.S. Declaration of Independence and Bill of Rights represent an authoritative source of international legal norms. Indeed, contemporary international law displays an even more explicit debt to these documents by identifying an “International Bill of Rights” as the very cornerstone of a binding, worldwide human rights regime. It follows from all this that any U.S. initiative to punish and prevent certain international crimes by assassination could sometimes represent essential support for international law directly, and for our own founding national principles.

The U.S. Government and Assassinations

Where exactly must a U.S. government now stand on the subject of assassination? In essence, we have seen that assassination can be both patently illegal and overwhelmingly lawful or even law-enforcing. Which judgment is correct? What should be the correct position of U.S. policymakers on this delicate subject?

To answer this question we should first recall that this country has, as an incontestable matter of fact, engaged in assassination, both in wartime and
peacetime. Whatever the status of pertinent prohibitions, on occasion our leaders have decided for themselves that assassination is purposeful—that it is “cost-effective” for the national interest.

Several U.S. presidents are authoritatively alleged to have approved assassination of certain foreign leaders during the Cold War. These targets of assassination included Cuba’s Fidel Castro (unsuccessful) and Chile’s Salvador Allende (successful). According to a Select Senate Committee that studied these plots, “United States Government personnel plotted to kill Castro from 1960 to 1965. American underworld figures and Cubans hostile to Castro were used in these plots, and were provided encouragement and material support by the United States.” William Colby, former Director of the CIA, has corroborated this assessment.

The most significant consequence of the Cuban Missile Crisis was that it exacerbated the Kennedys’ fury over Castro and intensified their determination Assassination and Targeted Killing to use the CIA and its covert action capability “to get rid of him,” with all the ambiguity the phrase includes.

The “successful” assassination of Allende grew out of the Chilean coup of 11 September 1973. Moreover, a Select Senate Committee concluded that in
addition to the Cuban and Chilean cases, and to particular cases involving the Congo, the Dominican Republic, and South Vietnam, ranking officials of the United States Government authorized “a generalized assassination capability” within the Central Intelligence Agency. From the standpoint of national and international law, however, these assassination plots were all illegal.

Although they were likely conceived with the intent of enhancing this country’s national security, they were assuredly a manifestation of concern
not for peremptory norms of international law, but for Realpolitik (or “power politics”). Such concern is not a permissible rationale for any transnational use of force, including assassination. Although there may be a residual right of assassination as a particular form of anticipatory self-defense (in addition to the rationales offered above), there was never any reason to believe that threats posed by Cuba and Chile were sufficiently immediate and overwhelming to warrant the invocation of this right.

What about this country’s resorts to assassination during a war? Enemy officials may meet the requirements for combatant status under international
law so long as they operate within the military chain of command. Therefore, enemy officials may qualify as lawful targets under this reasoning.  Under these assumptions, international law may permit assassination of enemy leaders, provided that the victim qualifies as a combatant under the laws of war. However, this contrary argument effectively ignores the position codified by the Hague Convention No. IV at Article 23(b).

International law may permit assassination of enemy officials during wartime despite the contrary rule of Hague Convention No. IV because: (a)
technically, assassination could be construed to fall outside the scope of behavior designed “to kill or wound treacherously,” and (b) under certain circumstances the necessity of assassinating an enemy official overrides applicable treaty prohibitions. The first rationale relies primarily on a “linguistic” solution to the conflict while the second rationale invokes the historic origins of international law in natural law.

In the United States, William Colby, as a former Director of Central Intelligence, argued that this country should refrain from assassinations except during “active war situations.” Consistent with this position, Colby headed the very controversial Phoenix Program during the Vietnam War, which identified and rooted out the “secret Communist apparatus” within South Vietnam—the socalled Viet Cong Infrastructure (VCI). Working closely with the Special Branch of the Vietnamese Police, Phoenix (or “Phuong Hoang” in Vietnamese) operatives assisted and carried out assassinations against the VCI.

From the standpoint of national and international law, these United States sanctioned killings represented clear and egregious violations of humanitarian international law. Without even considering antecedent questions concerning lawfulness of the war itself, questions of jus ad bellum, or “just war,” these assassinations contravened the codified and customary rules of armed conflict, which are rules of international law fully incorporated into U.S. municipal law. No jus cogens or peremptory norms existed to override these codified and customary prohibitions of assassination.

This does not mean that national and international law always prohibits assassination during wartime. Had the Allies succeeded in assassinating Hitler or Mussolini during World War II, or had the Coalition forces assassinated Saddam Hussein during the Gulf War, these efforts would have plausibly constituted legitimate, law-enforcing measures. A utilitarian, or “balance-of-harms” calculation would have supported this conclusion.

In contrast to the Phoenix-directed assassinations during the Vietnam War, the killings of Hitler, Mussolini, and Saddam would have lessened greatly the mount of total suffering in war and after war, hastened the processes of war-termination, and fully coincided with the binding expectations of discrimination, proportionality, and military necessity.

Abhorrent as it may seem, assassination does have its proper place as an enforcement mechanism under international law. To be sure, this place is small and residual, but it must still be acknowledged. Although an optimal world legal order would contain neither victims nor executioners, such an arrangement of global power and authority is presumptively not on the horizon.

From the particular standpoint of the United States, past abuses, double talk, and double-standards concerning assassination should not automatically prevent such an “extraordinary remedy” from achieving more purposeful and lawful expressions. Whether one likes it or not, assassination, like war, will not simply go away. The point, therefore, is not to pretend and to manipulate, but to operate within clear constraints and jurisprudentially correct standards.

Next Steps

Ideally, our U.S. president—in conjunction with certain others in the “in Assassination and Targeted Killing international community”—would sometime set to work on a “Draft Code” concerning assassination. An expected outcome of any such codification effort, one which would have substantial precedent in international law, could be a stricter regulation of assassination as a transnational activity, and also corollary
reductions in associated peripheral harms (reductions bringing assassination within the ambit of humanitarian international law). The only alternative would be “business as usual”: pretending that assassination is not a matter of concern under international law.

Such pretense would not inhibit the actual incidence of assassination, and it would almost certainly ensure a continuing incapacity to bring such killing under effective jurisprudential guidelines and control. If, however, one can accept that so intrinsically an uncontrollable activity as war should be regulated by law, we should also be able to accept the notion of appropriately codified regulations for assassination.

Significantly, such acceptance would be perfectly consistent with certain classical writings on the subject, writings identified, at Article 38 of the Statute of the International Court of Justice, as an authoritative “subsidiary means for the determination of rules of law.” For example, Cicero, in his speech in defense of Milo, supports assassination as anticipatory self-defense. Elsewhere in the same speech, Cicero offers enthusiastic support for assassination as tyrannicide.

We have come full circle. Although we should surely hesitate to commend assassination in any form (including targeted killing) as a remedy “to be boasted of,” we should just as surely reluctantly recognize it as a remedy that is sometimes indispensable. From the point of view of the United States, the imperative I have prescribed is that the president abandon assassination altogether as a cynical weapon of Realpolitik (more often than not, a weapon that is not only employed illegally, but also counterproductively), but that we nonetheless maintain under very limited conditions its operational capabilities. These capabilities must be conceived and used very narrowly, with particular respect to the peremptory expectations of humanitarian intervention and/or anticipatory self-defense.

Always, their proper function is to save lives, to confirm our understanding that this is not yet the best of all possible worlds, and that, sometimes at least, the well-intentioned reluctance to use such force can only produce more corpses.

Many years back, the Florentine philosopher Niccolo Machiavelli underscored the dilemma of seeking to practice goodness in an essentially evil world: “A man who wishes to make a profession of goodness in everything must necessarily come to grief among so many who are not good.”

Recognizing this tragic state of affairs, Machiavelli proceeds to advance the arguments for expediency that have become synonymous with his famous (or infamous) name. With his placing of force at the very center of political theory, the author of The Prince situates himself in sharp contrast to Platonic and early Christian concepts of “good.” Rejecting both Plato’s argument that there is a distinctly knowable and objective “good” that leads finally to virtue, and also Augustine’s otherworldly idea of an absolute goodness, Machiavelli constructed his political theory on the assumption that “all men are potential criminals, and always ready to realize their evil intentions whenever they are free to do so.” In his subsequent instructions to the statesman on how best to rule in a world eternally dominated by force, Machiavelli advises “to learn how not to be good.”

It will be important for the U.S. government to understand the various complexities of different kinds of actors in world politics. More specifically, the country’s leaders will need to better understand the growing importance of certain non-state actors as legal persons, including sub-national terror organizations, and also assorted “hybrid” actors comprised of both state-sub-state components, or of exclusively sub-state ones.

Traditionally, international law was focused more-or-less exclusively on the behavior of states. Statehood, of course, is the core element of membership in the United Nations. Article 3 of the UN Charter specifies, inter alia, that “The original members of the United Nations shall be the states which, having participated in the United Nations Conference on International Organization at San Francisco, or having previously signed the Declaration by United Nations of 1 January 1942, sign the present Charter and ratify it in accordance with Article 110.” Article 4(1) stipulates: “Membership in the United Nations is open to all other peace-loving states which accept the obligations contained in the present Charter and, in the judgment of the Organization, are able and willing to carry out these obligations.”

The Charter itself does not proceed to define the term “state,” nor do either of the advisory opinions of the International Court of Justice that expressly concern UN membership requirements. The traditionally governing document on statehood requirements under international law remains the 1933 Convention on the Rights and Duties of States. Still, in the actual practice of world politics, both within and outside of the organized United Nations, non-states have become increasingly important and incontestably relevant actors.

In the Talmud, Rabbi Eleazar quotes Rabbi Hanina, who says: “Scholars build the structure of peace in the world.” Although there are very good reasons to doubt that long-term historical records actually support this once-hopeful observation, there is still good reason to recommend that the U.S. government consistently draw capably upon available scholarship and learning regarding core matters of war avoidance and counter-terrorism.


This essay is adapted from a larger article with Notes at The Brown Journal of World Affairs, Fall/Winter 2018.

Louis René Beres was educated at Princeton (Ph.D., 1971), and is Emeritus Professor of International Law at Purdue. His twelfth book, Surviving Amid Chaos: Israel’s Nuclear Strategy, was published in 2016. His other writings have been published in Harvard National Security Journal; Yale Global Online; World Politics (Princeton); Bulletin of the Atomic Scientists; Israel Defense; Parameters: Journal of the US Army War College; Special Warfare; Oxford University Press; The Jerusalem Post; Infinity Journal; BESA Perspectives; US News & World Report; The Hill; and The Atlantic.

His Terrorism and Global Security: The Nuclear Threat (Westview, first edition, 1979) was one of the first scholarly books to deal specifically with nuclear


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