A flurry of news reports during the final week of August detailed recent Israeli air strikes against Iranian affiliated groups in Iraq, Lebanon, and Syria. The Washington Post published an Editorial questioning the wisdom of this Israeli policy, though typically, and regrettably, utterly neglected to consider issues of legality. It did repeat the media mantra that “Israel has a right to defend itself from Iranian attacks,” but then failed to examine whether any of the Israeli strikes had been responding to actual or imminent armed attacks. A New York Times analysis of the escalation similarly avoided the legal questions.

The short answer, based on publicly available evidence (discussed below), would be that the strikes were unlawful. Only one of the strikes on Syria was reportedly responding to an imminent attack, which should thus make for a very short analysis on the legality of the rest of the strikes. But a brief and somewhat disjointed exchange among some international law scholars on Twitter last week raised some questions and advanced some arguments (to the extent Twitter can sustain such a thing) that suggested a perhaps more complex and interesting analysis. I explore that line of analysis here.

Some Facts

First, a brief review of some of the facts. Israel carried out several air strikes in July and August in Syria, Iraq, and Lebanon. For simplicity I will leave the strikes in Syria aside for now, and focus on the strikes in Iraq and Lebanon, though it should be understood that Israeli representatives have argued that most of the strikes (or those that have been acknowledged by Israel) served the same broad purpose of preventing Iran from establishing a weapons supply line through Iraq and Northern Syria to Hezbollah in Lebanon.

One blast near Beirut on August 26, which was acknowledged by Israel, was aimed at machinery deemed “vital to Hezbollah’s precision-missile production effort.” The Lebanese army subsequently reported that Israeli armed drones crashed in Beirut, causing damage to a Hezbollah media center, though they were suspected of targeting missile technology; and the Lebanese army fired on two other Israeli drones that had entered Lebanon’s airspace. Yet another strike reportedly targeted a facility of the Popular Front for the Liberation of Palestine near the Syrian border.

Israel is similarly suspected of conducting a number of air strikes in recent weeks in Northern Iraq. Two anonymous U.S. officials confirmed that Israel was responsible for strikes on munitions storehouses for Iranian-backed militias near Baghdad. Asked about attacks inside Iraq, Prime Minister Netanyahu quipped “Iran doesn’t have immunity anywhere.” On August 25 a drone strike in Qaim killed a commander of a militia known as the Popular Mobilization Forces (PMF), which is said to be supported by Iran. A powerful faction within Iraq’s parliament not only accused Israel of conducting the strikes, but referred to them as an act of aggression and a declaration of war, and called upon the U.S. to withdraw its troops from Iraq as a result. A Pentagon spokesman even went so far as to affirm support for Iraqi sovereignty, and to say that “[we] have repeatedly spoken out against any potential actions by external actors inciting violence in Iraq.”

No Self-Defense Justification

What then are the possible legal justifications for these uses of force in Lebanon and Iraq? In my review of the material that is publicly available in English, I have seen no real legal basis offered by Israel. One strike against Iranian forces near Damascus in Syria was reported to have been to prevent drone attacks against Israel that were said to be in the final stages of preparation. But on the Lebanese and Iraqi targets, the reporting suggests that Israel’s objective was primarily to prevent the establishment of a weapons supply line, and to degrade Hezbollah’s ability to develop and manufacture missiles. The New York Times quoted one “regional security official” (nationality not indicated) as saying that “Israel’s message to Hezbollah here, writ large, was: Keep manufacturing [missiles], and we will keep hitting you.” Israel has not, apparently, made any claim, formally or informally, that the strikes in either Lebanon or Iraq were aimed at preventing an actual or imminent armed attack.

Viewed in isolation, based on the facts as known, these strikes would thus appear to be clearly unlawful, in that they cannot come within the scope of the self-defense exception to the general prohibition on the use of force. There may be some readers inclined to object to this assertion by appealing to “preventative self-defense,” or to some of the more distorted formulations of imminence that characterize the “unwilling or unable” doctrine debate; but I do not propose to flog those dead horses here—Tom Ruys pretty much settles these issues in his seminal work on armed attack and self-defense. That said, there are other questions, those raised in the exchange on Twitter, that seem more interesting, and require widening the lens of analysis.

What if Ongoing Armed Conflict with Iran?

One such question was whether the strikes would be lawful if one assumes that Israel and Iran are in an ongoing international armed conflict, and Iraq and Lebanon had been unwilling or unable to contain a threat to Israel posed by Iranian forces from within their territory. There are a number of issues lurking in this question, but first and foremost there is the implication that the existence of ongoing armed conflict attenuates the operation of the jus ad bellum, in the sense that Israel would then not be required to satisfy the conditions for the use of force in self-defense. Can that be right?

Jus ad Bellum Extinguished by Jus in Bello?

Eliav Lieblich has pointed out that Israel takes this position, or something like it, with respect to its operations against Hamas in Gaza. Israel claims that because there is an ongoing armed conflict the principles of necessity and proportionality under jus ad bellum are redundant or no longer relevant. He has also suggested elsewhere that Israel likely takes the same position on Hezbollah in Lebanon, and perhaps has extended it to Iranian-supported militias in Iraq. As Lieblich notes, this “reflects the rather conservative view that once a situation of war exists, jus ad bellum ceases to constrain the use of force, which is now regulated by jus in bello alone.”

I would suggest that this “conservative” view is very much a minority position. It is one of the more controversial and less accepted aspects of Yorum Dinstein’s seminal work War, Aggression and Self-Defence. But it is important to note that even Dinstein makes a distinction between “all-out war” and hostilities “short of war” in his discussion of whether the principles of necessity and proportionality operate subsequent to the initial response to an attack. While he suggests that defending states are not constrained by these principles once an all-out defensive war has been joined, I do not understand him to make this claim in relation to all international armed conflicts, and certainly not to such low-level conflicts as may exist between Iran and Israel. So even if one were to accept Dinstein’s controversial views on this issue, they do not really support the idea that Israel was free of ongoing jus ad bellum obligations in this context.

The better view, then, is that jus ad bellum continues to operate, and that in particular the principles of necessity and proportionality continue to constrain the actions of the defending state, throughout the period of international armed conflict and regardless of the scale of the conflict. “War” and “hostilities short of war” are concepts from a bygone era. The use of force under jus ad bellum triggers the operation of jus in bello, but that triggering of jus in bello does not extinguish the operation of jus ad bellum. Even if this is so, however, the initial question would imply that Israel, in using force in this instance, would not have to satisfy the conditions for self-defense—that is, be responding to an imminent or actual armed attack—but rather only need show that an operation was necessary and proportionate in relation to a specific enemy threat within the context of ongoing hostilities. This would explain, so the argument goes, why there have been no claims by Israel of responding to armed attacks. This might be a valid legal position if the strikes had been against Iran itself, but not necessarily when Israel is striking Iranian forces within the territory of Lebanon and Iraq. And it is even less plausible when it comes to the initial Israeli strikes against Iranian-backed forces in a third country—to which we turn next.

The Modification of the Law of Neutrality

The question that arises at this point of the analysis is whether the modern U.N.-based jus ad bellum regime has modified the older laws of neutrality. The “unwilling or unable” doctrine in its original pre-Twentieth Century form, as Ashley Deeks’ work on the doctrine explores, was part of the law of neutrality. According to these principles, states in armed conflict were permitted to use force against enemy forces within the territory of a neutral state, if the neutral state was unwilling or unable to prevent those forces from posing a threat. But the law of neutrality has of course been necessarily modified by the collective security system established under the U.N. Charter.

One such modification, arguably, is that the Article 2(4) prohibition on the use of force has constrained the range of action available against non-belligerent states. The use of force against enemy forces located within the territory of a non-belligerent state would constitute a use of force against that state, and would thus arguably have to satisfy the conditions for self-defense—that is, the use of force would have to be a necessary and proportionate response to an actual or imminent armed attack by the enemy forces within the non-belligerent state’s territory—regardless of the existence of armed conflict between the two belligerents. In an armed conflict between Israel and Iran, Israel need not satisfy the “armed attack” condition for each strike against Iran, but it arguably must do so for strikes against or within third states, even if such strikes are targeting Iranian forces within those states. In other words, it must demonstrate that the Iranian forces are responsible for an actual or imminent armed attack, and that the territorial state is truly unwilling to either prevent such attacks or consent to Israel responding to them with force within their territory.

Use of Force Against NSAs and the Modern “Unwilling or Unable” Doctrine

The situation in this case is of course complicated by the fact that Israel’s strikes were not actually against Iranian forces, but rather against non-state actors (NSAs) said to be supported by Iran. The fact assumed for this entire analysis, that Israel and Iran are in an ongoing international armed conflict, would seem to have even less relevance to the legality of strikes against Iranian-affiliated NSAs in non-belligerent states. The situation actually begins to look more like those at the heart of debates over the post-9/11 formulation of the “unwilling or unable” doctrine, which has been relied upon by the U.S., Israel, the U.K., and a handful of other states to justify strikes against NSAs in non-consenting states.

That doctrine, as most fully formulated by Daniel Bethlehem and echoed by its state adherents, is understood to be part of the doctrine of self-defense. Now, as I have argued in a recent article, the doctrine thus formulated distorts the concept of imminence, degrades the threshold for armed attack, ignores the requirements for attribution, and dangerously conflates principles of IHL and state responsibility with those of jus ad bellum—but the point here is that even under the doctrine as embraced by Israel, it is an aspect of self-defense and thus requires that the use of force was a necessary and proportionate response to an imminent armed attack.

What is more, the doctrine contains a presumption that Israel request assistance or consent from the territorial state in advance of any strikes, which involves providing the territorial state (here Iraq and Lebanon) with information regarding the perceived threat, and giving the territorial state time to respond. A refusal to provide consent or assistance may indicate that the territorial state is truly “unwilling” to deal with the threat, and is thus “substantially involved” in the actions of the NSA. The ICJ has in several cases, beginning with the Nicaragua v. United States merits judgment, held that the attacks of the NSA must be attributable to the territorial state before a use of force against that state is justifiable, the test for which is that the state using force, here Israel, must show that the territorial state was “substantially involved” in the operations of the NSA—and the ICJ held that the provision of weapons and logistical support are not sufficient to meet the “substantial involvement” test.

In the case of Lebanon, many will be inclined to think that the Lebanese government is certainly “substantially involved” in the actions of Hezbollah. But in the case of the PMF in Iraq, that may not be at all easy to establish—and in any event, no such arguments have so far been made. There is certainly no indication that Israel sought either consent or assistance from either government. Nor, of course, has it claimed that there was ever any actual or imminent armed attack planned by the NSAs that could be attributed to the territorial states in the first place (and just to be clear, the “attribution” being discussed here is part of the doctrine of self-defense, not state responsibility—the tests are distinct). Attribution only matters if the NSA has engaged in an armed attack that can be attributed to the state. What is more, as I argue in my article on the “unwilling or unable” doctrine, defending states that rely on the doctrine have an obligation to provide the territorial states, and the international community more generally, with the legal basis for such actions, as well as significant evidence to support their claims.

One last point on attribution: In the absence of meeting the requirements for the exercise of self-defense, it would not matter if the actions of the NSAs could be attributed to Iran, rather than to the territorial states (Iraq and Lebanon here). Iran’s substantial involvement in the operations of the NSAs would not justify Israeli strikes against those NSAs in Iraq, which would be a use of force against Iraq, any more than Israeli strikes would be justifiable against Iranian forces in Iraq, unless the conditions for the exercise of self-defense are satisfied, as discussed above.


It should perhaps be said, in closing, that it seems very unlikely that Israel is, as a matter of law, in an ongoing international armed conflict with Iran. But that was the assumption underlying the initial question, which raised interesting issues worth exploring. A number of steps in this analysis have relied upon conclusions that are themselves the subject of ongoing and vigorous debate, and there was not room here to fully defend or explain each of them. But it is my understanding that these conclusions reflect the more widely accepted position in each case. And if this is right, the foregoing analysis would suggest that even if it were the case that Israel is in an ongoing international armed conflict with Iran, it would not significantly alter the analysis, and that Israel would still be required to show that the use of force against both Lebanon and Iraq was a justifiable exercise of the right of self-defense. And Israel has certainly made no effort thus far to explain how the strikes were necessary and proportionate responses to actual or imminent armed attacks. On the facts as currently known, it is hard to see how the Israeli strikes could be lawful.


Image: Popular Mobilization Forces members stand by a burning truck after a drone attack reportedly by Israel near Qaim border crossing, in Anbar province, Iraq Sunday, Aug. 25, 2019 (AP Photo).