License to Kill? Self-defense, Sovereignty, and the Laws of War in the U.S. Assassination of Qasem Soleimani

On January 3, 2020, two cars, a Toyota Avalon and a Hyundai Starex, lay in the middle of an access road, engulfed in flames. The convoy was the victim of a U.S. military drone used to carry out precision strikes against known terrorists in the region. But this time, the remotely piloted craft had a unique target: Qasem Soleimani, commander of Iran’s Quds Force, the clandestine operations wing of the Islamic Republic’s Revolutionary Guard Corps (IRGC). The demise of Soleimani and his entourage shortly after they landed in Baghdad International Airport immediately launched a global debate over the legality of his execution. Mainstream outlets, including CNN, BBC, and Times teetered between calling it a “killing” and an “assassination.” [1] Others, including the U.S. Department of State, vehemently disagreed, instead deeming it a “defensive strike” supported by “very solid intelligence.” [2]

Soleimani’s killing is anything but a clear-cut case. Questions of its legality and legitimacy rest on nuanced and competing understandings of some of the greyest zones of international law. While the United States justifies the attack as a lawful act of self defense against an imminent threat, critics, including prominent legal scholars, cite its occurrence on Iraqi soil, its preemptive and extrajudicial nature, and its disproportionate effect as evidence of its illegality or, at the least, its lack of legitimacy within international legal frameworks. I argue that the strike on Soleimani cannot withstand scrutiny under three lenses of international law: it failed to meet the “imminent threat” standard for self-defense, it violated Iraq’s sovereignty, and it breached fundamental humanitarian legal principles of distinction and proportionality. 

First, it should be noted that these international legal norms apply in normal times, that is barring unusual circumstances such as the existence of a state of war. And while few have argued that the United States and Iran were at war at the time of the strike, some have suggested that the two states could be said to have been “engaged in international armed conflict.” [3] Yet the United States had not declared war against Iran and then-president Donald Trump did not notify the U.S. Senate of hostilities as required by federal law. [4] That said, a context of ongoing armed conflict could supersede official declarations. This possibility, however, is negated by the absence of a U.S. claim, retroactive or otherwise, to an active state of war. The International Court of Justice (ICJ) has long advised against evaluating a state’s actions according to legal claims or interpretations with which the state did not publicly associate itself. [5] The only apparent claim of this sort is found in the final pages of an obscure U.S. Department of Justice memo which, while invoking the “law of war,” still falls short of asserting and cannot on its own retroactively declare the existence of a state of war. [6]

In the absence of ongoing conflict, a few avenues remain for a state to justify an attack on a foreign target. The one which U.S. officials by and large relied on requires that the target pose an imminent threat to U.S. national security, allowing the aggressing state to frame the operation as an act of self-defense, an inherent right of states under Article 51 of the United Nations (UN) Charter. [7] This right was explicitly invoked in the U.S. Ambassador’s letter to the UN Security Council (UNSC) the week after the attack, buttressed by allegations of active planning of terrorist attacks against U.S. diplomats and troops in the region by the Quds Force which Soleimani led. [8] Self-defense, however, is not meant to be easy to invoke. The UN Charter only allows aggression in self-defense in response to the occurrence of an armed attack against the aggressing state. Given that the United States related its killing of Soleimani to alleged impending actions rather than any attack which had already taken place, Article 51 cannot be used to justify the strike. 

In 2001, however, the United States dug for itself a fragile new exception found in an impressively antiquated corner of customary international law. That year, American president George W. Bush declared a war on terror in response to the events of September 11. Worldwide condemnation of the attacks gave way to nearly limitless support for rapidly evolving U.S. foreign policy, including a broad claim to the necessity to practice “preemption”: offensive actions that anticipate a threat rather than respond to an attack. [9] The rationale was that states cannot wait to suffer the losses of a terrorist attack in order to act against those responsible for planning it. Preemptive self-defense doctrine traces back to the oft-cited 1837 Caroline case, where U.S. Secretary of State Daniel Webster required an “instant, overwhelming” necessity for preemptive strikes. [10] That test now forms the basis for America’s modern conception of preemptive self-defense, widely seen as permissible under the UN Charter by scholars such as the University of Oxford’s Dapo Akende. [11]

By no means, of course, does the mere introduction of a new American rationale resolve questions of international law surrounding Soleimani’s death. The attack must still meet the stringent requirements laid out in the Caroline case. Notably, an imminent threat is not simply any perceived threat of a future attack, even if such a threat is real. Instead, imminence is present only when a threat leaves “no choice of means, and no moment of deliberation.” [12] U.S. President Donald Trump’s warning that his military would respond “perhaps in a disproportionate manner” to any Iranian retaliation, announced only days after the attack, is a likely indicator that more conservative albeit equally coercive means were available for containing Soleimani’s alleged offensive plans. [13] Moreover, evidence of Soleimani’s past involvement in actions against U.S. forces is not enough to justify his murder. The only avenue left for the United States is to prove that the drone strike on Soleimani’s convoy was necessitated by a real, imminent threat to U.S. territory or U.S. nationals. And of this, unceasing assertions were made: just a couple of days after the strike, U.S. National Security Advisor Robert O’Brien, Vice President Mike Pence, the Department of State, and President Trump himself had all claimed that the Iranian general was “plotting to kill” Americans at U.S. bases in Iraq. [14]

Less than two weeks after the strike, however, the facade was lifted. A slew of quotes and interviews from Congress members, intelligence officials, and, surprisingly, Secretary of Defense Mark Esper quickly revealed that all American intelligence amounted to was Trump’s guess that Soleimani was “probably” thinking of targeting a few U.S. embassies in the Middle East. [15] Neither did U.S. officials transmit to the Security Council intelligence to back up their invocation of Article 51. It is possible to conclude, then, that even if the U.S. approach to preemptive self-defense were adopted, Soleimani’s killing would fail to meet the “instant, overwhelming” necessity requirement laid forth in the Caroline test. [16] In presenting anything which would come close to justifying a preemptive strike, the United States had come up miserably short. 

Failing to prove that Soleimani posed an imminent threat is far from the U.S. military’s only legal hurdle. Soleimani’s assassination occurred in Iraq, meaning the United States had possibly violated Article 2(4) of the UN Charter, which prohibits offensive movements in another state’s territory. [17] This interpretation of the charter was cemented in international law by the ICJ’s 1986 opinion in Nicaragua v. United States, where the court reprimanded the latter for infringing on Niracagua’s sovereignty, rejecting in its ruling U.S. justifications built on self-defense doctrine similar to the ones made in defense of Soleimani’s killing. [18] Under the UN Charter, for a U.S. drone to be permitted to fly in Iraqi airspace, Iraqi consent would have had to be secured. [19] The United States failed to secure consent for its actions, and in turn the Iraqi government was not quiet about what it felt was a level of disrespect warranting expulsion of all U.S. troops from the country. [20]

To circumvent Article 2(4)’s prohibition on the use of force in another state’s territory, U.S. officials leaned on another Caroline-derived exception, namely that “customary international law permits a nation to defend itself against aggressors located inside another country when the host country is unable or unwilling to stop the hostilities” [21]. Yet in the Soleimani case, the United States never demonstrated that Qasem Soleimani was actively mounting hostilities at the time of the strike, nor did it show that the Iraqi government was either unwilling or incapable of restraining him. And even if those burdens had been met, they would still have collided with a more stringent requirement: a 2008 agreement explicitly bars the United States from using Iraqi territory for offensive operations [22]. On both counts, that of international legal norms and an existing treaty, the strike violated Iraqi territorial integrity. 

An analysis of the legality of Soleimani’s killing would not be complete without a review of its compliance with basic principles of humanitarian law, the first being due process and the right to life. The Universal Declaration of Human Rights, adopted by the UN General Assembly in 1948, guarantees both a right to life and a right to a “fair and public hearing by an independent and impartial tribunal” for any and all persons charged with violations of the law of nations. [23] States are expected to recognize due process protections even outside their own territorial boundaries, as emphasized in a 2011 European court’s ruling in Al Skeini v. United Kingdom. [24] Additionally, most U.S. justifications for the premeditated targeting of Soleimani revolve around his past involvement in attacks against U.S. personnel and civilians alike, but the punishment for these crimes would fall squarely within the purview of bodies such as the International Criminal Court. [25] Absent an imminent threat posed by Soleimani to specific human life, his assassination is most likely an arbitrary execution in violation of internationally recognized guarantees of life, liberty, and due process. 

A second core principle, that of distinction and proportionality, requires that any lawfully targeted attack discriminate between combatants and civilians, and that incidental harm not be excessive relative to the anticipated military advantage. This means that under the laws of armed conflict, that is even if the United States and Iran were in a state of war, and even if Soleimani was a lawful target, the means used to eliminate him must still bear international humanitarian law (IHL) norms in mind. The Geneva Conventions of 1949 prescribe that an attack must not be directed towards civilians or civilian objects, implicitly prohibiting methods which do not sufficiently discriminate between combatants and civilians. [26] U.S. policy, however, does allow civilians who are “functional” to a combatant organization to be targeted. [27] U.S. officials may claim pursuant to this that the civilians killed alongside Soleimani were functional to the IRGC’s operations. That determination, however, is debatable. A report by the UN Special Rapporteur on executions asserts instead that the attack failed to distinguish between combatants and civilians and furthermore failed to limit its impact to an amount proportional to the threat posed by Soleimani as well as to the military advantage his assassination provides, the latter two elements remaining, of course, in any case unsubstantiated. [28] 

The United States’ violations of international norms in Soleimani’s assassination should set off alarms among scholars and diplomats alike. Certainly many will think of the Soleimani case as an exposé of the inadequacy of the international legal system. And while that characterization may not be inaccurate, it is incomplete. Rather than reveal gaps in international law, Soleimani’s killing and the impunity with which it was executed is a testament less to the failures of international law and more to the phenomenon of its abuse by more resourceful, powerful states, a phenomenon which only intensifies in an era of rapid globalization. 

Edited by Cara Wreen

[1] Lister, Tim and Eve Bower. “Growing doubts on legality of US strike that killed Iranian general.” CNN, January 6, 2020. https://www.cnn.com/2020/01/06/middleeast/soleimani-strike-legality-doubts-us-iran-intl/index.html; Vick, Carl. “Why the U.S. Assassination of Iranian Quds Force Leader Qasem Soleimani Has the U.S. Bracing for Retaliation.” Times Magazine, January 3, 2020. https://time.com/5758250/qasem-soleimani-iran-retaliation/

[2] U.S. Department of State. “Senior State Department Officials on the Situation in Iraq.” January 3, 2020. https://2017-2021.state.gov/senior-state-department-officials-on-the-situation-in-iraq/

[3] Hodges, Scott A. 2020. “The Killing of Qasem Soleimani.” The Reporter. https://www.jagreporter.af.mil/DesktopModules/ArticleCS/Print.aspx?PortalId=88&ModuleId=22882&Article=2539536.

[4] Legal Information Institute. n.d. “50 U.S. Code § 1543 - Reporting requirement | U.S. Code | U.S. Law | LII / Legal Information Institute.” Law.Cornell.Edu. Accessed April 29, 2025. https://www.law.cornell.edu/uscode/text/50/1543.

[5] Milanovic, Marko. 2020. “The Soleimani Strike and Self-Defence Against an Imminent Armed Attack.” EJIL: Talk! https://www.ejiltalk.org/the-soleimani-strike-and-self-defence-against-an-imminent-armed-attack/.

[6] U.S. Department of Defense. 2020. “Statement by the Department of Defense.” https://www.defense.gov/News/Releases/Release/Article/2049534/statement-by-the-department-of-defense/.

[7] Office of Legal Counsel. 2020. Memorandum for John A. Eisenberg Re: January 2020 Airstrike in Iraq Against Qassem Soleimani. N.p.: Department of Justice.

[8] United Nations Office of Legal Affairs. n.d. “Chapter VII: Article 51 — Charter of the United Nations.” Repertory of Practice of United Nations Organs. Accessed April 29, 2025. https://legal.un.org/repertory/art51.shtml.

[9] Nichols, Michelle. 2020. “At U.N., U.S. justifies killing Iranian commander as self-defense.” Reuters, January 8, 2020. https://www.reuters.com/article/us-iraq-security-usa-un/at-un-us-justifies-killing-iranian-commander-as-self-defense-idU.S.KBN1Z809Q/.

[10] Webster, Daniel. 1983. The papers of Daniel Webster: diplomatic papers. 1841–1843 ed. Vol. 1. Hanover: Dartmouth College Press, 62.

[12] Reality Check Team. 2020. “Soleimani attack: What does international law say?” BBC, January 7, 2020. https://www.bbc.com/news/world-51007961.

[11] BBC News. 2020. “The U.S., Iran and Qasem Soleimani story explained in 400 words.” BBC, January 7, 2020. https://www.bbc.com/news/world-middle-east-51018120.

[12] Webster, The papers of Daniel Webster, 62. 

[13] Lubold, Gordon, Nancy A. Youssef, and Isabel Coles. 2020. “Iran Fires Missiles at U.S. Forces in Iraq.” The Wall Street Journal, January 7, 2020. https://www.wsj.com/articles/stampede-at-funeral-procession-for-iranian-commander-kills-35-11578390888.

[14] Duncan, Conrad. 2020. “Mike Pence insists Trump had ‘compelling evidence’ of imminent threat but that he can't make it public.” The Independent, January 9, 2020. https://www.independent.co.uk/news/world/americas/us-politics/mike-pence-trump-iran-soleimani-killing-evidence-threat-classified-briefing-a9276881.html.

[15] Baker, Peter, and Thomas G. Neff. 2020. “Esper Says He Saw No Evidence Iran Targeted 4 Embassies, as Story Shifts Again.” The New York Times, January 12, 2020. https://www.nytimes.com/2020/01/12/us/politics/esper-iran-trump-embassies.html.

[16] Webster, The papers of Daniel Webster, 62. 

[17] Galbraith, Jean. 2020. “U.S. Drone Strike in Iraq Kills Iranian Military Leader Qasem Soleimani.” American Journal of International Law 114, no. 2 (April): 313–23. 26910493, 317. 

[18] “Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. United States of America).” 1984. International Court of Justice. https://www.icj-cij.org/case/70.

[19] Naidu, M. V. 2002. “Security, Sovereignty, and Intervention: Concepts and Case Studies.” Peace Research 34, no. 1 (May): 33–58. 23608020, 35.

[20] Singh, Bilveer. 2020. “Implications of Soleimani’s Killing for South and Southeast Asia.” Counter Terrorist Trends and Analyses 12, no. 2 (March): 12–16. 26908279, 13. 

[21] Jackson, Stephen. 2023. “An Imperfect War: The Legality of the 'Soleimani Strike' and Why the Biden Administration Should Adopt Its Precedent for Future Operations in Iraq and Afghanistan.” Penn State Journal of Law and International Affairs 11, no. 1 (January): 33–107. https://elibrary.law.psu.edu/cgi/viewcontent.cgi?article=1335&context=jlia, 93. 

[22] Rudolf, Inna. 2020. “Protecting Iraq’s Sovereignty amid Geopolitical Tensions around Iran.” German Council on Foreign Relations. https://dgap.org/en/research/publications/protecting-iraqs-sovereignty-amid-geopolitical-tensions-around-iran.

[23] Boyle, DAV. 1960. “International Law and Human Rights.” The Modern Law Review 23, no. 2 (March): 161–72. 1091445, 168. 

[24] “CASE OF AL-SKEINI AND OTHERS v. THE UNITED KINGDOM.” 2011. European Court of Human Rights. https://hudoc.echr.coe.int/fre#%7B%22itemid%22:[%22001-105606%22]%7D.

[25] Callamard, Agnes. 2020. “The Targeted Killing of General Soleimani: Its Lawfulness and Why It Matters.” Just Security. https://www.justsecurity.org/67949/the-targeted-killing-of-general-soleimani-its-lawfulness-and-why-it-matters/.

[26] International Committee of the Red Cross. n.d. “IHL Treaties - Additional Protocol (I) to the Geneva Conventions, 1977 - Article 48.” International Humanitarian Law Databases. Accessed May 3, 2025. https://ihl-databases.icrc.org/en/ihl-treaties/api-1977/article-48.

[27] The Executive Office of the President. 2016. REPORT ON THE LEGAL AND POLICY FRAMEWORKS GUIDING THE UNITED STATES’ USE OF MILITARY FORCE AND RELATED NATIONAL SECURITY OPERATIONS. https://man.fas.org/eprint/frameworks.pdf, 20. 

[28] UN Special Rapporteur. 2020. A/HRC/44/38: Use of armed drones for targeted killings - Report of the Special Rapporteur on extrajudicial, summary or arbitrary executions. https://docs.un.org/en/A/HRC/44/38, 29.