Israel’s Operation Rising Lion and the Right of Self-Defense
On Friday morning, June 13, the Israel Defense Forces (IDF) launched Operation Rising Lion, a major strike against Iranian nuclear infrastructure and ballistic missile capability. The IDF also degraded Iran’s air defenses and targeted senior Iranian military leaders. Iran condemned the attack, claimed a right of self-defense under Article 51 of the UN Charter, and responded with drone and ballistic missile attacks, including targeting Israeli cities. Both sides are continuing their attacks, and the United States has come to the aid of Israel in defending against the missile attacks, as it had during previous Iranian missile attacks in April and October of last year.
Publicly, Israel primarily justified Operation Rising Lion on the basis of the threat posed by the acquisition of nuclear weapons by Iran, although it has yet to provide a detailed explanation, such as an Article 51 notification to the UN Security Council that it is acting in self-defense. Rather, the justifications offered to date have been crafted in broad terms. For instance, Prime Minister Benjamin Netanyahu has stated, “[W]e are defending the free world from terrorism and barbarism that Iran fosters and exports across the globe.” For him, the threat is existential: “We can’t leave these threats for the next generation. If we don’t act now, there will not be another generation. If we don’t act now, we simply won’t be here.” Israel’s defense Minister, Israel Katz, also highlighted the urgency of the need to strike: “Iran is more exposed than ever to strikes on its nuclear facilities. We have the opportunity to achieve our most important goal – to thwart and eliminate the existential threat.” In fact, Israel has asserted that there is an actual military plan to destroy Israel.
As will be explained, the timing of the operation is of particular legal significance. It comes on the immediate heels of the June 12 (the day before Israel struck) International Atomic Energy Agency’s (IAEA) finding that Iran was in non-compliance with its safeguard obligations under the Treaty on the Non-Proliferation of Nuclear Weapons, and the associated Comprehensive Safeguards Agreement. According to a Board of Governors Resolution, “Iran’s many failures to uphold its obligations since 2019 to provide the Agency with full and timely cooperation regarding undeclared nuclear material and activities at multiple undeclared locations in Iran … constitutes non-compliance.” Thus, “the Agency is not able to verify that there has been no diversion of nuclear material required to be safeguarded under the Agreement to nuclear weapons or other nuclear explosive devices.”
It is also significant that the strike occurred while the United States was actively negotiating with Iran on the nuclear issue. Indeed, the sixth round of those talks, which began in April, was scheduled for yesterday (June 15) in Oman. And as the prospect of Israeli action grew, President Trump stated, “I don’t want them going in because, I mean, that would blow it.” However, after the IDF struck, the President seemed to suggest that the talks had become futile: “I gave Iran chance after chance to make a deal. I told them, in the strongest of words, to ‘just do it,’ but no matter how hard they tried, no matter how close they got, they just couldn’t get it done.”
This was not the first IDF operation targeting another State’s nuclear capacity. On the contrary, it is consistent with the policy sometimes referred to as the Begin Doctrine, according to which Israel is said to have a right to prevent regional adversaries from acquiring nuclear weapons. The first such operation was Israel’s 1981 attack on Iraq’s Osirak nuclear reactor (Operation Opera). Although Israel justified the operation on the basis of anticipatory self-defense, the UN Security Council unanimously condemned it as an international law violation in Resolution 487. In 2007, Israel mounted a similar operation into Syria against a nuclear reactor in Al-Kibar (Operation Outside the Box). Perhaps most famously, Israel and the United States are alleged to have conducted the Stuxnet cyber operation against Iranian centrifuges at Natanz between 2009 and 2010.
In this post, I examine whether Israel had a colorable legal basis for launching the strikes under the jus ad bellum, the law governing the resort to force as an instrument of national policy. In that regard, I will focus on the primary public justification Israeli officials have proffered—Iran’s nuclear program—rather than the broader threat Iran represents. It is the former that provides the best legal argument for forcible defensive action at this time.
Before turning to that topic, allow me two caveats. First, there are numerous law of armed conflict (LOAC) issues that merit consideration, such as the targeting of civilian nuclear scientists (and whether they qualify as direct participants in the hostilities, a question dependent on the attendant facts) and the Iranian missile attacks into civilian population centers. I leave the treatment of those to another time. Second, I am not commenting on the strategic wisdom of Operation Rising Lion. I leave that issue to the strategists. My analysis is strictly limited to international law.
Anticipatory Self-Defense
Defense Minister Katz has described the operation as a “preemptive strike,” although it is unclear if this term was used in the colloquial sense or as the legal term of art. By the prevailing view in international law, the sole basis for a factually preemptive strike is acting in “anticipatory self-defense” in response to an “armed attack” pursuant to Article 51 of the UN Charter and customary international law. Such operations must comply with the conditions of “necessity” and “proportionality” (Paramilitary Activities, paras. 194, 237; Nuclear Weapons, para. 41; Oil Platforms, paras. 43, 73-74, 76; U.S. Department of Defense (DoD) Law of War Manual, § 1.11.5). If they do not, the action will itself violate the customary law prohibition on the use of force reflected in Article 2(4) of the UN Charter.
The threshold question in every self-defense analysis is whether the action that the purported defensive operation is meant to preempt qualifies as an “armed attack.” That a nuclear attack against Israel would qualify as a use of force at the requisite level of severity is self-evident.
Also self-evident is Israel’s compliance with the proportionality criterion. Proportionality in the law of self-defense limits the scale and scope of the response to that required in the circumstances to avert attack (as distinct from the LOAC proportionality rule, which addresses civilian harm). Clearly, the targets selected by Israel were surgically designed to degrade Iran’s capacity to develop a nuclear weapons capability and use it against Israel. Other strikes impeded Iran’s ability to react effectively, including those targeting Iran’s ballistic missile program (the primary conventional weapon Iran uses against Israel) and the “decapitation strikes” on Iranian military leadership. Such operations were well within the boundaries of the jus ad bellum proportionality criterion.
Necessity represents a more challenging criterion in this case. By it, forcible action is only permitted in self-defense if non-forcible alternatives have been exhausted or are reasonably unlikely to prove successful. A key aspect of necessity in the context of acting in anticipation of an armed attack is “imminency” (DoD Law of War Manual, § 1.11.5.1). It is well accepted that there is no right to engage in “anticipatory self-defense” (preemptive self-defense in lay terms) until an armed attack is imminent.
Traditionally, imminency was understood temporally, that is, a use of force meant to preempt an armed attack could only be engaged in immediately before the armed attack was to be launched. This standard gave diplomacy and other non-forcible means the maximum opportunity to resolve the situation before the victim State resorted to force.
However, the 9/11 attacks motivated a sea change in the law governing anticipatory self-defense. As noted in the U.S. 2002 National Security Strategy (NSS), in the 21st century, a devastating armed attack could be launched without warning. In particular, the NSS pointed to the risk that a surprise attack could employ weapons of mass destruction. As a result, a number of scholars began to consider a more suitable interpretation of international law according to which States would be able to effectively defend themselves in the face of such threats. I set my own views out in 2003 in a Michigan Journal of International Law article.
[I]t would be absurd to suggest that international law requires a State to “take the first hit” when it could effectively defend itself by acting preemptively. This being so, the correct standard for evaluating a preemptive operation must be whether or not it occurred during the last possible window of opportunity in the face of an attack that was almost certainly going to occur. Restated, it is appropriate and legal to employ force preemptively when the potential victim must immediately act to defend itself in a meaningful way and the potential aggressor has irrevocably committed itself to attack. This standard combines an exhaustion of remedies component with a requirement for a very high reasonable expectation of future attacks – an expectation that is much more than merely speculative.
Of particular relevance to the current situation, not only must the putative attacker harbor the intent to attack, but it must also have the “capability” to attack; after all, if the adversary cannot attack, an attack cannot be imminent. Failure to satisfy all three requirements (intent, capability, last opportunity) renders a forcible action “preventive” rather than anticipatory. Absent a Security Council resolution under Chapter VII of the UN Charter, there is no legal basis for such an operation (see Schmitt and Goodman, Heller).
This “last window of opportunity” test found traction in U.S. legal policy. For instance, in 2012, Attorney General Eric Holder observed, “The evaluation of whether an individual presents an ‘imminent threat’ incorporates considerations of the relevant window of opportunity to act … and the likelihood of heading off future disastrous attacks against the United States.” He explained that there is no requirement for the “President to delay action until some theoretical end-stage of planning – when the precise time, place, and manner of an attack become clear. Such a requirement would create an unacceptably high risk that our efforts would fail, and that Americans would be killed.”
Israel’s situation on June 13 was not a paradigmatic example of those that the window of opportunity approach was meant to address, but neither was it unambiguously inapplicable. The first question is whether Iran had irrevocably committed itself to attacking Israel. Putting aside the issue of the recent escalation in hostilities between the two countries for later discussion, I would note that Iranian leaders have long threatened to destroy Israel. The Supreme Leader, Ayatollah Ali Khamenei, has been making such statements for a quarter of a century. For instance, in 2010, he claimed,” Israel is going downhill toward decline and fall, and God willing, its obliteration is certain.” Five years later, he warned, “Israel will not see the next 25 years.” And this May, he was to the point: “The Zionist regime that is a lethal, dangerous, cancerous tumor should certainly be eradicated, and it will be.”
In this regard, it has been suggested that although “[t]here are many public statements by various Iranian officials over the years calling, expressly or impliedly, for Israel’s destruction …[t]hat kind of rhetoric … is mainly meant for domestic political purposes in Iran and does not, without more, directly translate to an intention of the Iranian leadership to use a nuclear weapon against Israel.” However, it strikes me that if the leadership, both military and civilian, of one country repeatedly calls for the destruction of another and appears to be moving towards acquiring the capability to fulfill that objective, it is not unreasonable for the latter to conclude the former will carry out its threat.
Two factors bolster the reasonableness of finding the criterion satisfied in the current case. First, if there is a degree of uncertainty as to whether Iranian leaders mean what they say, the risk of being wrong should be shouldered by the side making the threatening statement. Second, surely, States have more leeway when the threat of being wrong is undeniably existential. After all, recall that even the International Court of Justice was unwilling to rule out the defensive use of nuclear weapons when a State’s “very survival would be at stake” (Nuclear Weapons Advisory Opinion, para. 97). Conceptually, this is also congruent with the so-called Bethlehem Principles, namely Principle 8, which allows consideration of the scale of harm likely to result from inaction.
Even when the intent to attack is manifest, the attacking State must be able to carry it out. Here, no one is claiming that Iran has a nuclear weapon, and Iran has repeatedly denied that it is building one. In fact, back in March, Director of National Intelligence Tulsi Gabbard observed, “[t]he IC [Intelligence Community] continues to assess that Iran is not building a nuclear weapon and Supreme Leader Khamenei has not authorized the nuclear weapons program he suspended in 2003.” That said, she quickly cautioned, “In the past year, we have seen an erosion of a decades-long taboo in Iran on discussing nuclear weapons in public, likely emboldening nuclear weapons advocates within Iran’s decision-making apparatus. Iran’s enriched uranium stockpile is at its highest levels and is unprecedented for a state without nuclear weapons.”
IAEA condemnation of Iran last week for failing to cooperate confirmed Gabbard’s concerns. The organization’s inability to rule out the possibility that Iran is in the process of building such a weapon was even more to the point. Iran certainly appears to be taking measures that can only be explained as engaging in such an activity.
The Israeli dilemma is that this development is taking place behind the curtain. Moreover, the process of building a nuclear weapon lends itself to quickly assembling one, again without Israel’s knowledge. And once that has been done, it could be rendered nearly impervious to attack by storing it underground; numerous Iranian facilities related to the nuclear program are already underground, making effective attacks against them very difficult. Again, given the risk posed by nuclear weapons, it is not unreasonable to extend the condition of capability to the likelihood of near-term acquisition of that capability, especially when it can be easily rendered immune to attack.
Finally, there is the last window of opportunity. The question is whether Israel had to act on June 13 lest it lose its ability to effectively defend itself against an Iranian nuclear attack. As just pointed out, Israel’s operational window to preempt an Iranian attack might have closed had it not acted, for once an Iranian weapon goes underground, it will be too late to act anticipatorily under most scenarios.
More problematic from the legal perspective is whether there were viable options short of using force that remained available to address the situation. President Trump had given Iran 60 days to “make a deal”; the Israeli strike occurred on the 61st. Yet, further U.S.-Iranian negotiations were nevertheless scheduled for June 15, so it would appear that at least the United States believed there was still some diplomatic light at the end of the tunnel (unless the meeting was scheduled as a coordinated U.S. and Israeli deception). And the IAEA’s condemnation of Iran’s lack of cooperation in the Agency’s work could be seen as likely to generate further diplomatic exchanges. Indeed, under Article XII.C of the IAEA Statute, the Board of Governors’ finding required referral to the UN Security Council and General Assembly for consideration.
The question is whether the door remained open to a diplomatic solution or whether further negotiations were a fool’s errand. In an interview on June 13, Israel’s Ambassador to the United States made it clear that Israel had concluded Iran was determined to acquire a nuclear weapon.
We were skeptical from the outset. We encouraged the talks because it’s important to try to pursue a path of negotiation, rather than a military one. But the fact of the matter is that the Iranians are ideologically and theologically committed to destroying Israel. And they have no intention whatsoever of drawing back their nuclear program, nuclear weaponization program.
And the IAEA condemnation could be seen as closing a door to further progress. Indeed, Iran’s reaction included assertions that it would build a new enrichment facility “in a secure location” and that “other measures are also being planned.”
If Israel was correct that diplomacy had proven fruitless, it was reasonable to conclude that the last window of opportunity was about to close, thereby opening the door to a forcible solution. And the fact that the negotiations were still underway between Iran and the United States presented an operational opportunity to strike, for Iran’s guard was likely somewhat lower during the ongoing talks. Yet, the situation on June 13 can also be interpreted as signaling that the window of opportunity remained open, and Israel acted precipitously.
To summarize, by the traditional temporal approach to imminency, Operation Rising Lion did not fulfill the preconditions for anticipatory self-defense. But that rigid standard has been supplanted by an interpretation more attuned to contemporary threats, one that allows States to use force anticipatorily when an adversary is committed to an armed attack using capabilities it wields, and the targeted State must act now lest it forfeit its ability to defend itself effectively. A colorable argument can be made that these criteria were satisfied on June 13, but such an argument requires a somewhat liberal interpretation of each. In my view, the nuclear (inter alia) nature of the threat Israel reasonably believes it is facing also bears on the appropriateness of such an interpretation. And if the operation was lawful, U.S. actions to defend against Iran’s retaliation are a lawful exercise of the right of collective self-defense.
Yet, a colorable argument also can be made that the situation Israel faced on June 13 fell short on one or more of the criteria, especially that allowing for action only when the defending State is liable to lose the opportunity to mount an effective defense. If so, Operation Rising Lion was, therefore, a use of force in violation of the prohibition resident in Article 2(4) of the UN Charter and customary law (see, e.g., Milanovic).
This interpretation would raise the question of the United States’ operation in defense of Israel. There is generally no right, individual or collective, to defend against actions undertaken pursuant to the jus ad bellum right of self-defense. Nevertheless, if reports that Iran is targeting population centers in addition to military targets are accurate, the United States is entitled to help Israel defend against them, for unlawful actions (targeting civilians and civilian objects in violation of LOAC) do not satisfy the necessity criterion of self-defense and therefore are themselves unlawful uses of force (armed attacks) triggering the right of individual and collective self-defense. Obviously, the analysis of the current situation is highly fact dependent.
An Ongoing Armed Conflict
Anticipatory self-defense is the proper topic upon which to base an analysis of the Israeli strike. However, an additional justification for the Israeli operation that is sure to surface is that there was already an ongoing international armed conflict between Israel and Iran at the time Operation Rising Lion was launched. This being so, some experts would suggest that the operation should be judged on the basis of the law of armed conflict; only the initial resort to force is subject to the jus ad bellum. By this approach, the law governing anticipatory self-defense is inapposite to the IDF’s current operations.
The key proponent of the view was the late Yoram Dinstein, who opined that “[t]he condition of necessity does not stand in the way of waging a war of self-defence until the enemy is utterly crushed and no longer poses an effective military menace,” and that “[o]nce war is raging, the exercise of self-defense may bring about the destruction of the enemy’s army regardless of the conditions of proportionality” (p. 282-83). Dinstein’s approach would certainly justify depriving the adversary of a potential nuclear capability.
In my estimation, there is no question that Israel and Iran had long been “at war” on June 13. To cite but a few noteworthy examples of qualifying hostilities, in April 2024, the IDF struck a building associated with the Iranian Consulate in Damascus, leading to an Iranian missile and drone attack on Israel that month, which was, in turn, replied to with an air strike on an Iranian radar site. In September, Israel killed a Hamas leader in Tehran, and the following month, Iran launched another ballistic missile salvo into Israel. Moreover, since Hamas’s October 7, 2023, attack (and even well before), there have been frequent exchanges between Israel and proxy groups directly supported by Iran, such as Hezbollah, the Houthis, and Hamas. For policy reasons, there may be hesitancy in acknowledging the ongoing armed conflict, but that does not detract from the factual reality that it has been underway on land, at sea, in the air, and in cyberspace for quite some time.
Although a Dinstein analysis should never be easily dismissed, I do not share his understanding in this case (see also Milanovic). Instead, I support the view preferred by most experts, according to which the jus ad bellum and the law of armed conflict are distinct bodies of law (see also Sassoli and Mačák) that apply in tandem.
I am not suggesting that every operation must be independently assessed against the self-defense criteria; such a standard would be operationally unworkable. Indeed, so long as future operations are reasonably foreseeable and hostilities have been relatively uninterrupted, there is a continuing right of self-defense. And the very existence of hostilities can bolster the case for satisfaction of the anticipatory self-defense criteria discussed above. But when a significant shift in the nature of the conflict occurs, as is the case with the targeting of Iran’s nuclear assets following a relative lull in the fighting, it is appropriate to reassess whether there is a basis for that particular use of force and whether it complies with the conditions of proportionality and necessity (see also Greenwood, p. 223).
Concluding Thoughts
This is a tough case on both the facts and the law, one about which reasonable lawyers can—and will—disagree. That Iran represents a significant threat to Israel is beyond doubt. The fact that the threat is nuclear renders it existential. It is not a threat that Israel can ignore, and, in my opinion, the severity of the threat affords Israel greater leeway under the jus ad bellum than would be the case with a lesser threat. But whether Operation Rising Lion comports with the right of anticipatory self-defense, even in light of the greater leeway merited by the nuclear factor and using the last window of opportunity test as the standard of assessment, is a question that will ultimately be judged against facts that likely will be long contested. For me, a claim that the operation was lawful is colorable, but not incontestable.
***
Michael N. Schmitt is the G. Norman Lieber Distinguished Scholar at the United States Military Academy at West Point. He is also Professor of Public International Law at the University of Reading and Professor Emeritus and Charles H. Stockton Distinguished Scholar-in-Residence at the United States Naval War College.
The views expressed are those of the authors, 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
Photo credit: IDF Spokesperson’s Unit
