On April 21, 2026, Reed Rubinstein, the Legal Adviser at the U.S. Department of State, issued the Trump administration’s lengthiest explanation of its views on the international law justification for the U.S. war against Iran, Operation Epic Fury. Both the timing and presentation of this statement were unusual in terms of the U.S. government’s past practices. The statement arrived almost two months after the president started the war. To its credit, the statement was presented as an opinion of the Legal Adviser, posted publicly on the State Department’s website. Publicly articulating the U.S. government’s international legal arguments on highly contested issues is a positive development that should be embraced. Unfortunately, the substance of this new justification is both legally unpersuasive and analytically confused.
The core legal arguments of the Rubinstein statement are that:
“Epic Fury is only the latest round of an ongoing international armed conflict with Iran. …[T]he United States is engaged in this conflict at the request of and in the collective self-defense of its Israeli ally, as well as in the exercise of the United States’ own inherent right of self-defense.”
But the bottom line remains that the United States has failed to show that either Israel or the United States suffered an armed attack by Iran, which is necessary to justify the use of force in self-defense. The Rubinstein statement’s repeated claim of an ongoing armed conflict is a true red herring. As with the March 10th Article 51 letter to the UN Security Council, this U.S. statement fails to establish that President Donald Trump’s war of choice is anything other than what it appears—a manifestly illegal use of force in violation of the UN Charter. The Trump administration needed to bring something else to the discussion to overcome that conclusion. The statement reveals there is nothing there.
Although this statement provides transparency – and may serve as a rebuttal to recent critiques (such as a letter from international law experts and my own prior analysis – this defective and overly permissive justification risks further eroding legal constraints on the use of force.
Legal Background
Under international (and domestic) law, the UN Charter sharply restricts the use of force by States. Article 2(4) of the treaty prohibits “the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.”
Article 51 of the Charter in turn specifies, in relevant part, that
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 measures necessary to maintain international peace and security. Measures taken by Members in the exercise of this right of self-defence shall be immediately reported to the Security Council
Thus, notwithstanding the prohibition on the use of force imposed by Article 2(4), the forcible measures by States in individual or “collective self-defense” (acting to defend another State) are permissible and must be reported to the UN Security Council.
Critically, the text of the Article 51 requires an “armed attack” as a prerequisite for the use of force in self-defense. Beyond that, the United States and other States have endorsed the concept of anticipatory self-defense in response to an imminent threat of armed attack as customary international law. While some have advocated for a right of States to use force in preventative self-defense against more inchoate threats, consistent with the weight of State opinio juris and expert opinion, the U.S. government has never adopted this theory of preventative self-defense.
To the contrary, in 1981, in response to a preventative Israeli attack on an Iraqi nuclear facility at Osirak, the United States joined a unanimous UN Security Council resolution in “strongly condemn[ing] the military attack by Israel in clear violation of the Charter of the United Nations .” In the view of the United States, Israel’s actions violated Article 2(4) due to the
“absence of any evidence that Iraq had launched or was planning to launch an attack that could justify Israel’s use of force. … [T]he presence in a State of the military capacity to injure or even to destroy another State cannot itself be considered a sufficient basis for the defensive use of force.”
Further, the possession of nuclear weapons (which, to be clear, Iran did not and does not possess) by itself would not even constitute an unlawful threat of the use of force, much less entitle other States to actions in self-defense. The United States took the position before the International Court of Justice (ICJ) in the Nuclear Weapons case. The United States submitted: “With respect to a threat to use nuclear weapons in a particular case, such a threat may or may not be lawful – just as a threat to use conventional weapons may or may not be lawful – depending on the circumstances in question.” Consistent with this view, in its advisory opinion (para 47-48), the ICJ declined to endorse the argument that possession of nuclear weapons by itself constituted an unlawful threat of the use of force. More broadly, the mere possession of weapons, conventional or otherwise, does not justify the resort to armed force absent an imminent threat of armed attack.
Also of potential relevance in the case of Iran, in some circumstances a State’s support to a non-State actor engaging in an armed attack gives rise to a right of self-defense against the supporting State (in addition to the non-State actor). As articulated by the ICJ in the Paramilitary Activities case, the right of self-defense may be engaged by “‘the sending by or on behalf of a State of armed bands, groups, irregulars or mercenaries, which carry out acts of armed force against another State of such gravity as to amount to’ (inter alia) an actual armed attack conducted by regular forces, ‘or its substantial involvement therein.’”
As Michael Schmitt and Alexander Hernandez have noted, in the context of Iran’s support for regional armed groups, a key issue is not just whether a State “sends” armed bands but whether State support amounts to “substantial involvement” in armed attacks by the armed groups. In the view of the ICJ, the mere arming and equipping of an armed group, or the provision of logistical or other support, does not amount to an armed attack giving rise to the right to use of force in response.
Any use of force in the exercise of self-defense is also subject to the customary international law requirements of necessity and proportionality. For the use of force in self-defense to be lawful, it must be necessary. As explained by the State Department’s Legal Adviser in 2016, the “international law of self-defense requires that such uses of force be necessary to address the threat giving rise to the right to use force in the first place.” As articulated in the Caroline correspondence between the United States and the United Kingdom, the “necessity of self-defence” requires “no choice of means.” Thus, in order for the use of force to be necessary, peaceful alternatives to addressing the supposed threat—including diplomacy—must be unavailable or exhausted.
“Oceania had always been at war with Eastasia”—The Ongoing Armed Conflict Theory
The Rubinstein statement asserts that Operation Epic Fury was launched in the context of ongoing international armed conflicts between the United States and Israel with Iran. “The operations recommenced in late February were part of an armed conflict with Iran that has been ongoing for years and, at the least, since June 2025.” This ongoing armed conflict legal theory echoes the Trump administration’s revisionist historical narrative that the United States has been at war with Iran for 47 years, since the 1979 hostage crisis—an Orwellian rewriting of the past that may have come as a surprise to many Americans.
There are layers of problems with the administration’s ongoing armed conflict theory.
In the first place, the claim of an ongoing armed conflict is directly at odds with the Trump administration’s own prior statements. The administration repeatedly stated that the June 2025 war with Iran is over and ended, contrary to the statement’s assertion that the “parties did not make unilateral declarations concerning an end to hostilities.” For example, in June 2025 President Trump himself declared the 12 Day War with Iran to have come to an “Official END.” And in October 2025, the State Department proclaimed on social media that Trump, the “PRESIDENT OF PEACE” had ended “8 wars in 8 months” and listed the “Iran and Israel” as one of the conflicts supposedly ended.
Second, the statement’s central thesis continues to conflate the body of rules determining when States are in an “armed conflict” for purposes of applying the Geneva Conventions (jus in bello) with the body of rules for when a State may resort to force in self-defense (jus ad bellum). This problem is obvious to international lawyers (see Adil Haque’s discussion of “Armed Attack and Armed Conflict”). A telltale sign of the error is the statement’s reliance on commentaries by the International Committee of the Red Cross for rules governing the end of armed conflict – despite the well known fact that the ICRC avoids any analysis of jus ad bellum as outside its organization’s mandate. What’s more, the legal threshold for an international armed conflict is exceedingly low: the ICRC commentaries themselves note, relying on U.S. practice, that a state of armed conflict may be created “after the capture of just one member of their armed forces” (emphasis added). It is thus nonsensical to claim there is no need to assess jus ad bellum in an ongoing armed conflict (which may be triggered by a single ongoing detention), and yet the statement makes that claim throughout.
Third, the Rubinstein statement does not specify with precision when either Israel’s or the United States’ supposedly ongoing armed conflicts with Iran began. Instead, with respect to both countries, the statement hedges by claiming that hostilities have been ongoing since at “least” certain dates (with alternate dates given in different parts of the statement). Such ambiguity obscures the issue of how these armed conflicts began and whether it was in fact Iran that launched the predicate armed attack—or whether Israel and the United States attacked first. By way of comparison, Russia may be engaged in an ongoing armed conflict with Ukraine but that does not alter whether Russia’s attack upon Ukraine was illegal in the first place. Nor would anyone even suggest Russia’s invasion of Ukraine in February 2022 was not a violation of the UN Charter because Russia and Ukraine were already in an armed conflict following Russia’s invasion of Crimea and occupation through proxies of parts of Eastern Ukraine. It would be a laughable argument.
Fourth and relatedly, through invoking a supposed ongoing armed conflict, the Rubinstein statement seeks to skirt the jus ad bellum requirements of necessity and proportionality. The statement asserts that “[a]s a matter of international law, there is no requirement to continually reassess jus ad bellum principles of necessity and proportionality in the context of an ongoing armed conflict.” It cites instead a prior speech by then-State Department Legal Adviser Brian Egan, which makes a very different claim (namely, that “once a State has lawfully resorted to force in self-defense against a particular armed group following an actual or imminent armed attack by that group, it is not necessary as a matter of international law to reassess whether an armed attack is imminent prior to every subsequent action taken against that group, provided that hostilities have not ended.”) (emphasis added). The statement cites no other authority for this proposition regarding necessity and proportionality — a position which is inconsistent with international law, including as interpreted by the United States.
As the U.S. government explained in a 2016 framework produced after extensive interagency consultation by career subject matter experts, “the use of force in self-defense in an ongoing armed conflict is limited by respect for States’ sovereignty and the considerations discussed above, including the customary international law requirements of necessity and proportionality when force could implicate the rights of other States.” In other words, States do need to reassess the jus ad bellum requirements of necessity and proportionality even in an ongoing armed conflict. And as explained below, the Trump administration has failed to establish that the use of military force is necessary.
Finally, if the United States had been engaged in an ongoing armed conflict with Iran since at least June 2025 (as the statement claims), then the Trump administration would be using military force in violation not only of the U.S. Constitution, which explicitly grants Congress the authority to decide when the nation goes to war, but also of the 1973 War Powers Resolution. The War Power Resolution (amongst other things) imposes a 60-day time deadline for the removal of U.S. armed forces from hostilities not authorized by Congress. President Trump’s attacks against Iran in 2025 and 2026 lacked congressional authorization and the 60-day clock for this supposedly ongoing armed conflict would have long expired.
No Predicate Armed Attacks against Israel or the United States
The Rubinstein statement’s ongoing international armed conflict theory therefore does not obviate the jus ad bellum requirement of a prior armed attack or threat of an imminent armed attack for the exercise of lawful self defense. But the statement also fails to establish that specific armed attacks provide the predicates for either the exercise of individual or collective self defense.
The legal justification (correctly) states that “[a]ny serious legal assessment of U.S. combat activities must be anchored in the relevant material facts.” Yet, the statement’s factual narrative is imprecise, omits critical information, and is inconsistent with prior claims by the first and second Trump administrations. Moreover, the justification devotes considerable space to a catalogue of legally extraneous details of Iran’s rhetoric, ideology, and bad acts, including with respect to its support for non-state actors such as Hizballah, Hamas, the Houthis, and paramilitaries. Without establishing that those facts bear on the exercise of individual or collective self defense, the factual recitation reads as an airing of grievances rather than substantiation for rigorous legal arguments.
With respect to armed attacks against Israel, the statement seems to suggest that Hamas’ atrocities of October 7th, along with Iran’s own drone and missile attacks of April and October 2024 may provide the predicates for the use of force against Iran. There are several holes in any such theory.
In terms of Hamas’ attack of October 7th, the statement does not explain how that assault constitutes an attack by Iran under international law. As for Iran’s barrages against Israel in 2024, both followed attacks by Israel on Iran. In April 2024, Israel conducted a fatal attack against Iranian officials in an Iranian government facility in Damascus, Syria. As for Iran’s October fusillade against Israel, Tehran justified it by reference to preceding Israeli attacks inside Iran against a Hamas official in Tehran and an Iranian general in Lebanon.
Regarding attacks on the United States, the statement recites a litany of attacks on U.S. personnel and armed forces in the Middle East since 1979. But apart from the sacking of the U.S. Embassy in Tehran and taking of U.S. diplomats as hostages, it fails to specify how these attacks are imputable to Iran so as to give rise to a right of self defense against Iran. (Notably absent from this list of misdeeds is President Trump’s allegation of Iranian responsibility for the attack on the USS Cole.)
The Rubinstein statement identifies no attacks by Iran against Israel or the United States since the end of the 12 day war in June 2025. Nor, contrary to other rhetoric by the administration, does the statement rely on a theory that Iran posed an imminent threat of an armed attack. (The abandonment of this imminent threat argument follows a similar progression in Trump’s first term of shifting and inconsistent justifications for the Soleimani strike.)
No Necessity
I wrote in March with respect to the Trump administration’s earlier justification of Operation Epic Fury in its Article 51 letter to the United Nations:
The fundamental problem with any attempt to justify Operation Epic Fury on the basis of self-defense is that the U.S. attack was unnecessary. Far from being a war of necessity, the Iran War is a war of choice. And it was Trump’s choice.
The Rubinstein statement does nothing to alter this assessment.
In addition to failing to specifically identify the armed attacks that could give rise to a right of self defense, the statement does not establish that the use of military force was necessary as a matter of jus ad bellum—that the United States had exhausted all peaceful means to address whatever threat Iran posed.
The selective history presented in the statement omits that the United States had successfully employed diplomacy to tightly constrain Iran’s nuclear program, subject to international verification—until President Trump withdrew from the nuclear deal known as the Joint Comprehensive Plan of Action (JCPOA) in 2018. Moreover, it is not plausible for the administration to argue it had exhausted diplomacy with Iran in either 2025 or 2026. The Trump administration did not mount a serious diplomatic effort remotely on par with that which the Obama administration used to negotiate the JCPOA or the interim deal that preceded it. The administration’s 2025 negotiations with Iran were terminated not because they were futile, but due to Israel’s surprise attack on Iran in the midst of the talks. Similarly, rather than the February 2026 negotiations having reached a dead end, according to the Omani mediators speaking shortly before the U.S. attack on Iran, negotiations were due to continue the following week with technical discussions.
More fundamentally, these U.S. negotiations with Iran were not aimed at stopping an armed attack or imminent threat of armed attack. Even if they had failed after extensive good faith efforts, the inability to reach a diplomatic arrangement satisfactory to the United States (or Israel) on Iran’s nuclear program does not give rise to a right of self defense against Iran absent an actual or imminent armed attack.
Unfortunately, it is clear that the United States attacked Iran not because of the necessity of self defense, diplomacy having been exhausted, but judging from his own repeated statements, because President Trump sought to do a “Venezuela” in Iran. Emboldened by the tactical success of the decapitation raid into Caracas, Trump hoped for another short and sweet military spectacle that decapitated the regime, resulting in a new more pliant leader taking the helm. It turns out, of course, that Iran is not Venezuela.
A Standard to be Met, for Critical Reasons
As explained in the opening words of the UN Charter, the “Peoples of the United Nations [agreed to the Charter] to save succeeding generations from the scourge of war, which twice in our lifetime has brought untold sorrow to mankind.”
Yet like all laws, the UN Charter and its prohibition on the use of force is not self implementing. The treaty therefore requires human beings—U.S. government officials, including the President of the United States and his advisors—to faithfully execute its provisions. The principal and vital objective of the Charter—avoiding the ruinous bloodshed and destruction of war—depends on the senior government lawyers advising Trump and his Cabinet to treat the law as a standard to be met even when their policy counterparts are pressing for a particular outcome.
As with the U.S. Constitution, the UN Charter sharply limits recourse to force for very good reasons. We are currently witnessing the consequences of the failure of the President’s advisors and senior most lawyers to adequately convey these rationales—thousands of dead (including U.S. servicemembers), millions displaced, global economic pain , a vital waterway obstructed, and a U.S. President flailing to extricate himself from a mess of his own making.
