The Soleimani Killing -Trump’s Legacy for International Law

Facts of the Case

Tensions in the Middle East significantly worsened after Major General Qassem Soleimani was assassinated by a US air strike at Baghdad Airport on Friday, 3rd January, 2020. Donald Trump, the US President at the time, had authorized the strike by opting for what seemed to be the most hostile measure that had been presented to him.[1] For Iranians, Qassem Soleimani was considered to be a hero against ‘the oppressors in the West’. He was perhaps the most central person in the country after the Supreme Leader, Ayatollah Khomeini. On the other hand, his reputation in the US, especially within government ranks, was that of a tyrant who wished to eliminate as many Americans as possible.[2] Such reputation has also been evident from the extensive support shown in favor of the strike by the Republican Party.[3]

In response to an attack on an Iraqi military base that had left an American civilian dead and amidst a threat of further large-scale armed attacks, the following options had been presented to the US President on 28th December 2019: Launch strikes on Iranian ships, or missile facilities, or against Iranian-backed militia groups in Iraq. The choice of directly targeting General Soleimani was also presented, but mostly to make other options sound convincing.[4]

Before moving forward, it is crucial to establish that the possibility of a significant threat to US citizens was in itself questionable. There were conflicting views in the administration. On one hand, General Milley, Chair of the Joint Chiefs of Staff said that his information regarding the attacks was “clear and unambiguous”. On the other hand, other officials termed Soleimani’s “suspicious” movements as “a normal Monday in the Middle East”.[5]

The President chose to attack militia groups. The strikes were successful and there was no collateral damage. In an unforeseen turn of events, the Iranians as well as the Iraqis considered the attacks to be out of proportion. Their response was to storm the American Embassy.

This left Mr Trump raging and he finally opted for the elimination of Major General Soleimani. The justification for such action lies in a deep-rooted ‘line’ set by the President and his aides, which the Iranians had seemingly crossed. The Iranians, cleverly dodging that line through secluded attacks, finally crossed it when Kataib Hezbollah attacked a US military base in Kirkuk, Iraq.[6]

It must be noted, however, that non-compliance with a mere warning through word of mouth does not constitute a violation of international law.

According to a more realistic justification provided by the US, American citizens in Iraq had been under a threat of imminent attack, based on intelligence regarding General Soleimani’s visits to his forces in various regions.[7] This is the crux of the matter to be debated upon under the lens of international law.

The justification triggers the following questions regarding the legality of the action:

  • To what extent does international law warrant the use of force based on the threat of an armed attack?
  • How is the imminence of the threat determined?

Rules of International Law

I. Article 51

If the parties involved in a conflict are not already engaging in continuous armed conflict with each other, then the ‘first use’ of military strike must be justified in accordance with jus ad bellum. The foremost principle of jus ad bellum is the “prohibition on the use of force”, which is an unconditional norm as per the United Nations Charter, Article 2(4).[8] An exception to this rule only exists in the circumstances of ‘self-defence’, which will be discussed further in light of Article 51 of the UN Charter and other principles of international humanitarian law (IHL), also referred to as the law of war (not to be confused with international human rights law).

In order to navigate through international law to answer the preceding questions, we must first refer to Article 51 of the UN Charter which states the following:

“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 the measures necessary to maintain international peace and security. . . .”[9]

The Article conspicuously outlaws the use of force under any circumstances but two:

  • when the use of force is authorized by the UN Security Council;[10]
  • when a state acts in self-defence in response to armed attacks that have occurred or are in the process of occurring.[11]

Application of Article 51

In the case at hand, Iran had taken no action that could be termed as an armed attack on the US. However, according to senior officials, there was certainly a threat of attack. Soleimani had recently visited his Quds force in Syria, Lebanon and Iraq and the officials claimed that there was reason to believe that armed attacks on US embassies and consulates were not only possible but could also claim hundreds of lives.[12] Although no prior approval had been sought from the UN Security Council (UNSC), the US justified its actions under self-defence.

Even if the US administration could somehow provide a reason for the strike to be an act of self-defence, Article 51 still required it to report the action to the Security Council.[13]

Having said that, Article 51 does not provide adequate information to conclusively deal with cases where an armed attack has not yet occurred, but only where there is a threat of such attacks.

II. Anticipatory Self-Defence

In cases where Article 51 fails to be of much help, “anticipatory self-defence”[14] can be claimed whereby an armed attack or strike has not yet occurred, nor is in the process of occurring, but is anticipated to occur.

While preventive or anticipatory self-defence is generally considered to be unlawful,[15] the doctrine is still widely debated, largely reiterating that anticipatory self-defence can only be deemed lawful if an attack is ‘imminent’. This means that states cannot act unilaterally and authorize attacks based on threats that are hypothetical, unsubstantiated or conjectural.

The same position was also validated by the UN Secretary General’s High Level Panel which concluded anticipatory self-defence to be lawful only if a threat had been ‘imminent’. Distinction was made between cases where a threat did exist but had not been imminent, for instance in case of acquisition of nuclear weapon-making capability. In such cases, the Panel has held that matters must either be taken to the UN Security Council or dealt without force.[16]

Application of Anticipatory Self-Defence

The rule affirms that for a claim of self-defence in response to attacks that have not yet occurred but are threatened to occur, the threat of the attack must be imminent in nature.

How is imminence to be established? For that, the Caroline Criteria must be fulfilled.

III. The Caroline Criteria

Another instrument of international law that may be taken into account while determining the legality of President Trump’s actions is the ‘Caroline Test’. This test concerns a state’s right to act first in anticipatory self-defence. For such a right to be warranted, there are two requirements that need to be fulfilled:

  1. Necessity: “The use of force must be necessary because the threat is imminent and thus pursuing peaceful alternatives is not an option.”[17]
  2. Proportionality: “The response must be proportionate to the threat.”[18]

For the purpose of determining whether or not these two requirements have been fulfilled in Soleimani’s case, they must first be defined. The requirement of necessity indicates that a state must not have had any other reasonable alternative to shield itself from the ‘imminent’ attack. The requirement of proportionality exists to make sure that any use of force is in line with the magnitude of the imminent attack which is being responded to. These two requirements, as recently defined by the honourable Queen’s Counsel, George Brandis and most experts, are essential to legitimize any claim or action in anticipatory self-defence.[19]

Application of the Caroline Criteria

It is evident from the above discussion that the threat of imminent attack was questionable in itself as not even officials in the US administration could develop consensus on it, so it seems highly unlikely that the instantaneous use of force had been absolutely necessary to preserve the sovereignty of the USA. It is even more unlikely that pursuing an alternative strategy was not an option, since President Trump had been presented with a number of options from which he chose the most disruptive one. The requirement of necessity does not appear to be fulfilled.

Furthermore, the US President responded to the death of one American serviceman by killing Iran’s second-in-command. The response was considered highly disproportionate, as had also been reflected in the Iranian protests and reactions in the Middle East. More worrisome was the President’s Tweet on the matter which did not rule out disproportionate response to any Iranian aggression but in fact encouraged it.[20] This window of disproportionality should not have been opened if the US wanted to legitimize its actions. The requirement of proportionality also does not appear to be fulfilled in the case at hand.

In this regard, Eliav Lieblich, an associate professor of law at Tel Aviv University aptly concluded,

“It is hard to square the US’s objective of ‘deterring future Iranian attack plans’ with mainstream understandings of anticipatory self-defence.”[21]


Looking at this conflict through the lens of international law, it can be reasonably concluded that Mr Trump’s actions cannot be justified legally. The legality of the action largely depended on the evidence of an imminent attack. Merely generalizing that Soleimani was ‘planning an attack’ could not be considered as adequate justification. No supporting evidence had been presented, apparently because no such evidence perhaps even existed.

It may be deduced from the information currently available that the threat of the attack may not have been very imminent as Trump not only had other alternatives at his disposal but would have had more windows of opportunity as well. The action taken by him under ‘self-defence’ was also not completely necessary at that point in time. Moreover, his response was certainly not proportionate to the severity of the attack that had already occurred, or the magnitude of any future attacks that could occur. Lastly, and most importantly, it must be kept in mind that even if any evidence of a threat of future armed attacks existed, it was not conclusive, as reflected by the conflicting views in the administration. It would have been unlikely for the administration to disagree over the magnitude of the threat had the evidence been conclusive.

It is also submitted that Twitter is perhaps not the appropriate medium to give out ultimatums and legal notices. Encouraging war crimes is no way to de-escalate a conflict. Does Donald Trump want to be remembered as an advocate of war? History has never been kind to warmongers and war criminals, even if they have the best of intentions.


[1] Cooper and others, ‘As Tensions With Iran Escalated, Trump Opted for Most Extreme Measure’ (New York Times, 4 January 2020) <>
[2] Nectar Gan, ‘Who was Qassem Soleimani, the Iranian commander killed by a US airstrike?’ (CNN, 3 January 2020) <>
[3] Emily Stewart, ‘Democrats warn of the dangers of war while Republicans fall in line after the killing of Iran’s Qassem Soleimani’ (Vox, 3 January 2020) <>
[4] Cooper and others, ‘As Tensions With Iran Escalated, Trump Opted for Most Extreme Measure’ (New York Times, 4 January 2020) < >
[5] ibid.
[6] Marc Thiessen, ‘In killing Soleimani, Trump enforces the red line he drew on Iran’ (The Washington Post, 4 January 2020) < >
[7] Demirjian and others, ‘Trump’s team offers mixed messages about ‘imminent’ attack from Iran as justification for killing Soleimani’ (The Washington Post, 8 January 2020) <>
[8] OConnell Mary ellen, ‘The Killing of Soleimani and International Law’ (EJIL: Talk, 6 January 2020) <> accessed 7 April 2020
[9] UN Charter, Article 51
[10] Alex Potcovaru, ‘The International Law of Anticipatory Self-Defense and US Options in North Korea’ (Lawfare, 8 August 2017) <>
[11] ibid.
[12] Reuters Staff, ‘Inside the plot by Iran’s Soleimani to attack US forces in Iraq’ (Reuters, 4 January 2020) <>
[13] John Bellinger, ‘Does the US Strike on Soleimani Break Legal Norms?’ (Council of Foreign Relations, 6 January 2020) <> accessed 6 April 2020
[14] George Brandis , ‘The Right of Self-Defence Against Imminent Armed Attack In International Law’ (Blog of the European Journal of International Law, 25 May 2017) < >
[15] Kevin Heller, ‘Why Preventive Self-Defense Violates the UN Charter’ (OpinioJuris, 7 March 2012) <>
[16] Monica Hakimi, ‘North Korea and the Law on Anticipatory Self-Defense’ (Blog of the European Journal of International Law, 28 March 2017) <>
[17] The Caroline (exchange of diplomatic notes between Great Britain and the United States, 1842), 2 J. Moore, Digest of International Law 409, 412 (1906)
[18] ibid.
[19] George Brandis , ‘The Right of Self-Defence Against Imminent Armed Attack In International Law’ (Blog of the European Journal of International Law, 25 May 2017) < >
[20] Mia Swart, ‘Trump, his tweets and international law’ (Al Jazeera, 8 January 2020) <>
[21] Mia Swart, ”To stop a war’: Did Soleimani killing violate international law?’ (Al Jazeera, 5 January 2020) <>

The views expressed in this article are those of the author and do not necessarily represent the views of or any organization with which he might be associated.

Sairam Hussain Miran

Author: Sairam Hussain Miran

The writer is a student of A Levels and President of the Cornelius Law Society at LGS JT Lahore, having organized Pakistan’s first online interschool law moot competition. He has keen interest in national politics and international law and has previously interned with the Research Society of International Law, conducting research on various international humanitarian law (IHL) issues. He has also completed an International Law Certification Course from RSIL.