Israel (and the United States) vs. Iran: Self-Defence and Forcible Counterproliferation
A number of experts have set out their position on whether Israel has a credible claim to self-defence as a legal basis for its recent and ongoing series of strikes against Iranian nuclear facilities. I would like to add a few comments to this discussion and offer my view as to why the Israeli airstrikes (recently joined by the United States) do not qualify as lawful self-defence. I will also discuss a number of possible alternative justifications or mitigations of responsibility for using force in the context of counterproliferation of weapons of mass destruction (WMD). The opinions and positions put forward are based on the available facts as of 23 June 2025.
Preventive War vs. Anticipatory Self-Defence
Various authors, including Michael N. Schmitt, Marko Milanovic, and Nicholas Tsagourias, have recently described different approaches to self-defence ranging from a restrictive view that allows no room for anticipatory or pre-emptive action to forestall an incipient attack to a very permissive interpretation that allows for preventive action to neutralize the capacity of a potential attacker to be able to mount an attack at some indeterminate point in the future.
According to one school of thought, this wider interpretation would be particularly applicable to situations where a potential attack with the use of WMD would be possible if a number of other considerations seem to have been fulfilled. These include: a record of hostile acts and or posture over a period of time; the capability of the hostile actor to mount such an attack within the reasonably foreseeable future; and whether or not other alternatives are available (a.k.a. “last window of opportunity”).
Another possibility, put forward by Cohen and Shany, is that the latest series of strikes is part of an ongoing armed conflict. I will not address this view here because others have already put forward arguments why this is not the most persuasive way to view the current conflict.
There seems to be broad agreement among these commentators and in general that self-defence does not bar anticipatory action in situations where there is clear evidence of an impending armed attack in the reasonably proximate future. Where a handful of States and experts differ from the mainstream view is that they take the position that in situations where a terrorist attack or an attack with the use of WMD is potentially possible and a particular actor poses a threat, the temporal consideration that the attack must be likely to take place within a reasonably proximate timeframe is not realistic and therefore should be rejected.
Needless to say, acceptance of such an interpretation would make self-defence virtually synonymous with preventive war. A potential attack that has not yet materialized and which might be conducted at some indeterminate point in the future is a long way from the prevailing reading of either Article 51 of the Charter or the customary law on anticipatory self-defence based on the Caroline criteria even if one does not take the temporal criterion of imminence literally. Consequently this interpretation neither reflects the overwhelming majority view on the legal considerations relating to self-defence, nor any controlling interpretation of how international opinion has reacted to this “brand” of self-defence in relation to inter alia the 2003 invasion of Iraq and the “global war on terror” (p. 130-40).
Even if narrowed down to situations where a particular actor has engaged in (repeated) hostile acts in the past and continues to remain an adversary with a hostile stance and is engaged in attempts to gain access to WMD, there must be at least persuasive evidence that the actor in question is capable of launching a potentially serious attack in the foreseeable future, that the actor has taken concrete steps (at least to prepare) to engage in such an attack and that other options to prevent the attack are not available or would not be capable of forestalling the attack.
On the basis of publicly available evidence regarding the current conflict, there is a lack of consensus on whether Iran is close to developing a nuclear weapon and the means to deliver it. And there is no open sign that it is engaged in or even about to engage in concrete preparations to mount a nuclear attack on Israel or anyone else. Finally, it does not seem persuasive that all alternatives to a military strike on Iran’s nuclear facilities were exhausted at the time Israel commenced its aerial campaign against Iran, followed a few days later by direct U.S. intervention in the form of aerial bombardment of three Iranian nuclear facilities. Most notably, negotiations were still ongoing when Israel (followed by the United States) commenced military action.
Hence, the military action by Israel and the United States does not qualify as self-defence on the basis of prevailing interpretations of what constitutes self-defence in response to an imminent armed attack (even if defined broadly) which would justify measures aimed at forestalling such an attack. The Israeli and U.S airstrikes have much more in common with preventive war to a strategic challenge than with any current reading of self-defence.
Other Alternatives to Self-Defence?
Assuming the Israeli and U.S. strikes do not qualify as lawful self-defence, the question may be posed as to whether there are any alternative legal justifications for them. The quick answer to this is that there are only two accepted legal bases for the use of force between States or by a State across an international border or demarcation line and neither of these applies in the case at hand.
However, is it possible to see the wide interpretation of self-defence to cover potential attacks that have yet to materialize but which might be conducted by a hostile actor sometime in the future—even months from the time action is taken—as a new “exception” to the Charter prohibition? The fact that some States and experts have embraced this interpretation in relation to situations where a hostile actor is attempting to gain access to WMD raises the question whether a right of “forcible counterproliferation” has emerged or is emerging. If so, how would such a right fit into the current legal framework regulating the use of armed force?
Past episodes of such armed action to prevent a hostile actor gaining access to WMD do not point in the direction of the emergence of such a new right. The Israeli bombardment of the Osirak reactor in 1981 was generally deemed unlawful at the relevant time, even by Israel’s close ally, the United States. In 2007, Israel again engaged in a preventive strike against a suspected nuclear reactor in Syria, this time without much public outcry due to the secrecy of Israel in conducting the attack and of the Syrian regime in relation to the destruction of an unreported nuclear facility. Neither case shows any appreciable support for the proposition that armed action aimed at preventing a hostile actor from gaining access to WMD has emerged as a new legal justification for the use of force. No attempt was made to cloak the action in such a justification at the relevant time and there is no sign that such a justification has subsequently gained general acceptance.
It should be pointed out that silence or expressions of “understanding” do not qualify as evidence of opinio juris in support of a new rule or interpretation of customary law. Moreover, it would be difficult, if not impossible, to fit such a new “exception” to the prohibition on the use or threat of force into the Charter framework relating to the use of force. The prohibition is widely accepted as a peremptory norm which means that the entirety, or at least the overwhelming majority of the international community would have to accept such a new legal claim for the use of force for it to be lawful. That is hardly likely, to say the least, so the possibility can be safely dismissed.
Finally, the possibility should be considered that such preventive action, while lacking an accepted legal basis, could be deemed acceptable or at least not subjected to more than symbolic condemnation on grounds of overriding necessity or public policy aimed at curbing the proliferation of nuclear weapons and preventing them coming under the control of a hostile actor. Proponents of humanitarian intervention, without a clear legal basis in the form of a UN Security Council mandate, have long argued that such action is or should be deemed acceptable, even if not lawful. The same could possibly be said of certain other forms of the use of force that do not neatly fit into either recognized legal basis for the use of force.
There are dangers in accepting quasi-legal justifications for the use of force, but at the same time there have been situations where force has been used in the absence of a clear legal basis that have escaped condemnation or even garnered a reasonable degree of acceptance without the entire legal framework on the use of force having been overturned.
The naval quarantine of Cuba in 1962 (p. 206-08) the use of force by NATO in the Kosovo crisis of 1999 (see The Kosovo Report: Conflict, International Response, Lessons Learned), and perhaps the abovementioned Israeli strike on the Syrian nuclear reactor at Al Kibar in 2007 are all potential candidates for such excusable if not lawful action. But in all these cases, the possibility of a negotiated settlement was virtually non-existent at the time the measures were taken. Moreover, the force was calibrated to address the emergency situation without exacerbating the situation beyond what was required to address the emergency. Only under these conditions would an unlawful action qualify for some degree of acceptance or tolerance.
Whether that would be the case with regard to the recent bombing campaign against Iran is questionable. Firstly, it is not clear that there were no other avenues to address the problem and potential threat posed by Iran’s nuclear program in view of the fact that negotiations were ongoing when the bombing campaign commenced. Secondly, the degree of force that has been employed seems clearly excessive if the aim was to simply degrade the Iranian nuclear program and induce Iran to engage in negotiations leading to the (drastic) reduction of its enrichment capacity. The use of “bunker buster” bombs to “obliterate” nuclear facilities, the targeting of the Iranian military leadership and nuclear scientific establishment and demands for “unconditional surrender,” accompanied by implicit threats of regime change do not readily qualify as carefully calibrated emergency measures that can be deemed as unavoidable and excusable, if not lawful.
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Terry D. Gill is Professor Emeritus of Military Law at the University of Amsterdam, having held the chair from September 2001 until September 2020.
The views expressed are those of the author, and do not necessarily reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense.
Articles of War is a forum for professionals to share opinions and cultivate ideas. Articles of War does not screen articles to fit a particular editorial agenda, nor endorse or advocate material that is published. Authorship does not indicate affiliation with Articles of War, the Lieber Institute, or the United States Military Academy West Point.
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