The US drone strike on Qassem Soleimani, one of the most important members of the Iranian leadership, raises many complex questions of international law. This post will examine the lawfulness of the strike from the standpoint of the law on the use of force. It will first set out the parameters of the US justification for killing Soleimani, which is some variant of self-defence against an imminent armed attack. It will then look at the notion of an imminent attack, at the different ways such an attack can be repelled, and at whether, on the facts as we know them, the US strike should be regarded as lawful.
I will argue that even if one accepts a broad theory of self-defence against an attack that is yet to occur, such as that espoused by the US government itself, the strike is likely to be unlawful. It is improbable that the US would be able to meet the factual requirements that it needs to justify the strike – in particular, there are serious doubts that there even was an imminent attack, and there are serious doubts that the method the US chose to resist that supposed attack was necessary under the circumstances. If such was the case, the US breached the prohibition on the use of force in Article 2(4) of the UN Charter vis-à-vis both Iran and Iraq. Finally, the post will look at the illegality of the threats of further use of force made by President Trump against Iran, which are unlawful both as a matter of the jus ad bellum and the jus in bello.
The US justification for the strike on Soleimani
It is clear that the US is relying on self-defence to justify its strike against Soleimani. It is also clear that the US is relying on self-defence not in the context of an ongoing armed attack by Iran, but with regard to a future armed attack or attacks, which the US considers to have been imminent. Thus, the initial statement of the US Department of Defense justifying the strike said that ‘the U.S. military has taken decisive defensive action to protect U.S. personnel abroad by killing Qasem Soleimani’ and that the ‘strike was aimed at deterring future Iranian attack plans.’ Subsequent statements by President Trump, his Secretary of State and National Security Advisor repeatedly referred to planned imminent attacks by Iran against the US which necessitated the killing of Soleimani:
“Soleimani was plotting imminent and sinister attacks on American diplomats and military personnel but we caught him in the act and terminated him,” Trump told reporters at his Mar-a-Lago resort.
No further detail of these imminent attacks has been publicly disclosed. While the US is yet to submit a formal letter to the UN Security Council pursuant to Article 51 of the Charter, which might clarify the US position further, it is clear that the various statements made by US officials were not purely political or designed for domestic consumption. They are a public justification for the use of force against another state, and are perceived as such by other states, with, for example, the UK Foreign Secretary saying that in his view the right to self-defence clearly applied. Self-defence against an imminent armed attack is thus the justification that the US government chose to employ for its actions, and it is against this justification that those actions should be judged. We should not ‘ascribe to States legal views which they do not themselves formulate’ (ICJ, Nicaragua, para. 266).
Now, crucially, that justification would have to work against both Iran and Iraq, because the strike took place on Iraqi territory without the consent of the Iraqi government. Pursuant to restrictivist theories of self-defence, such an argument would be a non-starter for the simple reason that Iraq was not implicated in any imminent attacks against the US. For expansionists, this situation would be analogous to self-defence against non-state actors – using force on the territory of the state in which the attacker is located would need to be justified by the necessity of stopping the attack, e.g. pursuant to an unwilling or unable theory.
In other words, the US would need to demonstrate that it had to strike at Soleimani when and where it did, that it could not ask the Iraqi government for permission (e.g. on the basis of its collusion with Iran) and that it could not wait to strike at Soleimani elsewhere. All of these points are contingent on facts yet to be established, and from what I can see it is unlikely the US could discharge this burden. Be that as it may, the remainder of this discussion will proceed on the assumption that the US could conceivably provide such a justification. I will turn now to the issue of imminence.
Self-defence against an imminent armed attack; prevention and deterrence
Readers are of course familiar with debates, old and new, about whether Article 51 of the Charter permits self-defence against armed attacks that are yet to occur. Some authors, like Mary Ellen O’Connell writing on the blog yesterday, are of the view that the language of Article 51 is clear and that it permits self-defence only against attacks that have actually occurred. Many others disagree. The notion of imminence has served as a focal point of arguments of those states and scholars who feel that confining self-defence solely to ongoing attacks would be too restrictive, but that embracing a theory of pre-emptive self-defence against any future attacks would be far too permissive. Imminence is thus a term deployed to create a theory occupying some kind of palatable middle ground.
More restrictive conceptions of imminence have seen it as a temporal concept, i.e. an imminent armed attack is one that is about to occur. More expansive theories of imminence have focused less on questions of time and more on those of necessity and causality. Recent years have seen concerted efforts by some scholars and states to push for such expansive conceptions of imminence – consider in particular in that regard the principles articulated by Daniel Bethlehem in the AJIL, subsequently embraced verbatim in the speeches of legal advisors of several powerful states (e.g. here and here).
While these efforts to expand imminence have often been conceptually muddled, it seems clear that the US and some of its allies, like the UK, do not see imminence in temporal terms. It is more of a rhetorical device than a genuinely useful legal concept – an armed attack will be regarded as imminent if responding to the attack is necessary now, regardless of when and how exactly the attack will take place (see here for an extended discussion, and the comments section in particular; see also Akande and Lieflander here). An imminent attack is thus one where the attacker has committed to particular aggressive course of action which they will not desist from absent some kind of intervention in the causal chain, such as a use of force in self-defence.
Let us then also proceed, for the sake of the argument, on the assumption that these expansive positions are correct, i.e. that self-defence is available against imminent attacks, and that an imminent attack is not defined as one that is about to occur, but as one which necessitates immediate defensive action to successfully repel it. Logically, there are two possible forms of such action.
Two basic ways of disrupting an imminent attack
First, the state acting in self-defence could use force against those persons or objects of the attacking state that will be used to execute the attack in the future. Think, for example, of an air strike against the attacking state’s tanks about to cross the border, or against their fuel supply lines. Second, the state acting in self-defence could use force against the assets of the attacking state that are not indispensable for the execution of the planned attack, with the purpose of exacting pain or damage on the attacking state so as to deter it from pursuing the planned attack.
Therefore, the first response disrupts the attacker’s ability to pursue the attack, the latter its will to do so. The first response is more easily squared with the exceptional nature of self-defence under the Charter; the second is in tension with the idea of imminence as an irrevocable commitment of the attacker to pursue the attack, and in many cases might be difficult to distinguish from an unlawful, punitive armed reprisal (see this EJIL article by David Kretzmer for an extensive discussion).
On the facts of the Soleimani strike, the US appears to have engaged in both types of response, or at least has offered both types of justification. Thus, Secretary of State Pompeo justified the killing by saying that:
“He [Soleimani] was actively plotting in the region to take actions – a big action as he described it — that would have put dozens if not hundreds of American lives at risk. We know it was imminent,” Pompeo told CNN, echoing an earlier Pentagon statement on Thursday.
“These were threats that were located in the region,” Pompeo added. “Last night was the time that we needed to strike to make sure that this imminent attack … was disrupted.”
Pompeo’s general idea here seems to be that killing Soleimani was necessary, i.e. this was the last opportunity to strike, and doing so did in fact prevent some (unspecified) attack, because Soleimani was actively involved in its planning. However, the various other statements of US officials (including the very first DoD one) are replete with references to deterrence, i.e. an attempt to influence decision-makers in Iran to desist from a particular course of action.
While it is certainly possible that killing Soleimani did have a concrete operational impact on some planned attack by Iran, the US has offered no evidence that such was the case. And Soleimani’s high-ranking position makes such an indispensable operational role unlikely; his role was in providing strategic direction and materiel to Iranian proxies in Iraq, not in the execution of specific operations. Thus, the ‘US Army General Mark Milley, the chairman of the Joint Chiefs of Staff, told reporters that violent plots by Soleimani might still happen despite his death.’
“There may well have been an ongoing plot as Pompeo claims, but Soleimani was a decision-maker, not an operational asset himself,” said Jon Bateman, who served as a senior intelligence analyst on Iran at the Defense Intelligence Agency. “Killing him would be neither necessary nor sufficient to disrupt the operational progression of an imminent plot. What it might do instead is shock Iran’s decision calculus” and deter future attack plans, Bateman said.
It might be argued that because of its enormous potential for escalation, even with the constraining influence of necessity and proportionality, the deterrence rationale should be categorically excluded from the legitimate scope of self-defence. But, even assuming its permissibility in principle, the basic problem with a deterrence rationale is that it is practically impossible to know ex ante whether a use of force for that purpose would actually work. Whereas the effectiveness of striking at assets directly involved in the planned attack is capable of at least some measure of objective assessment (e.g. destroying the tanks will in fact stop the attack), the same cannot be said, absent extraordinary circumstances, of an attempt to influence the attacking state’s ‘decision calculus.’ It in fact seems manifest that Soleimani’s killing had the exact opposite effect on Iran’s leadership, which has publicly committed to avenge him.
Obviously, it is impossible to know for sure whether Soleimani’s killing had some kind of deterrent effect without knowing anything about the specifics of the purported imminent attacks by Iran which this strike was designed to disrupt. But that is exactly my point – it seems unlikely in the extreme that the US government itself could have been able to reliably assess the extent of such a deterrent effect before it decided to kill Soleimani. Framed as deterrence, the strike just does not seem to work as intended. And if it is incapable of so working, it cannot be considered necessary for the purpose of Article 51.
To be clear, I am not saying here that any failed attempt at self-defence is ipso facto unlawful. Rather, if in the specific context the state purporting to act in self-defence has no idea whether a deterrent action will actually be able to stop an imminent attack, such an action is simply unsuitable for its stated purpose and accordingly cannot be necessary.
Was there in fact an imminent attack?
A further, logically prior problem for the US self-defence justification is that the existence of an imminent armed attack by Iran seems to be undermined by its own intelligence. According to a report in The New York Times:
But some officials voiced private skepticism about the rationale for a strike on General Suleimani, who was responsible for the deaths of hundreds of American troops over the years. According to one United States official, the new intelligence indicated “a normal Monday in the Middle East” — Dec. 30 — and General Suleimani’s travels amounted to “business as usual.”
That official described the intelligence as thin and said that General Suleimani’s attack was not imminent because of communications the United States had between Iran’s supreme leader, Ayatollah Ali Khamenei, and General Suleimani showing that the ayatollah had not yet approved any plans by the general for an attack. The ayatollah, according to the communications, had asked General Suleimani to come to Tehran for further discussions at least a week before his death.
Assuming that this report is factually correct, it seems difficult to qualify the supposed planned Iranian attack as imminent, for the simple reason that the person who had to decide on whether the attack will take place – Ayatollah Khamenei – was yet to make his decision. In other words, even if imminence was no longer a temporal concept but a purely causal one, as the US and other expansive theories of imminence argue, the planned attack was not imminent because Iran was yet to commit to that particular course of action.
Bottom line on the Soleimani strike
In conclusion, even if we took the US views of applicable international law on their own terms, fully accepting that self-defence pursuant to Article 51 of the Charter extends to imminent armed attacks, embracing an expansive, non-temporal conception of imminence, and accepting a wider scope of permissible goals in self-defence, it would be difficult to argue that the killing of Soleimani was lawful under the jus ad bellum (I leave aside here the issue of the legality of his killing under international humanitarian law (if it applied) or international human rights law). The US self-defence justification is factually contingent on a number of points.
It is only if the US could establish that (1) Soleimani was operationally involved in the planning of future attacks against US assets and personnel; (2) that Iran was committed to pursuing these attacks, i.e. that it was virtually certain that they would take place because a final decision had been made in that regard; (3) that killing Soleimani would in fact have disrupted those attacks; (4) that killing him was the only way of disrupting those attacks, i.e. that no options short of the use of force would have succeeded in disrupting the attacks; (5) that killing him in Iraq, at the time the strike took place, was necessary to disrupt those attacks – it is only then that the strike against Soleimani could arguably be lawful, even under broader theories of self-defence that the US government espouses. This would require a much more detailed disclosure of the relevant evidence and facts than are currently available.
It is in my view unlikely that the US could discharge this burden, but it is not inconceivable that it could do so. The Soleimani strike is thus not clearly unlawful in the way some previous military actions of the Trump administration have been (here and here). But it is imminently unlawful. The lack of any specific details provided publicly and the disclosure of US intelligence that goes against US interests cast serious doubts on whether the various factual predicates for lawful self-defence could be met even on a generous appraisal of the facts. Similarly, the deterrence rationale for killing Soleimani, even if admissible in principle, collapses under the weight of its own failure, a failure that was easily foreseeable.
Clearly unlawful threats to use force
This brings us, finally, to the one clear and unambiguous violation of Article 2(4) of the Charter – Trump’s threats by tweet against Iran after Soleimani’s killing, warning that in case Iran responds the US has:
….targeted 52 Iranian sites (representing the 52 American hostages taken by Iran many years ago), some at a very high level & important to Iran & the Iranian culture, and those targets, and Iran itself, WILL BE HIT VERY FAST AND VERY HARD. The USA wants no more threats!
— Donald J. Trump (@realDonaldTrump) January 4, 2020
Trump of course has some form in the crassness of his threats. And, faced with the criticism of his reference to attacking Iranian cultural sites – which would be a violation of IHL and potentially even a war crime – he characteristically doubled down:
Speaking to reporters aboard Air Force One a day later, he sought to offer a justification. “They’re allowed to kill our people,” Trump said, according to a pool report. “They’re allowed to torture and maim our people. They’re allowed to use roadside bombs and blow up our people. And we’re not allowed to touch their cultural site? It doesn’t work that way.”
I am afraid that it precisely does work that way (not that Iran is actually ‘allowed’ to do any of those things). One war crime does not justify another. Even putting aside the cultural site issue, Trump’s reference to 52 targets chosen to symbolize 52 American hostages taken in Tehran almost 40 years ago (all of whom ultimately lived to tell the tale), demonstrates the purely punitive intent behind his words. So does his reference, in yet another tweet, to a potentially ‘disproportionate’ (his word) US response. This is a very specific threat, especially when taken in its context; it cannot be dismissed as simple rhetoric. And not only is such language shameful coming from a President of the United States, but it lays bare the total arbitrariness behind the proposed use of force, which cannot be reconciled with any legitimate conception of self-defence in international law.