Written by Samantha Johnson

Introduction

Under Article 2(4) of the United Nations (“U.N.”) Charter, all Member States have an obligation to refrain from the threat or use of force against another State.¹U.N. Charter art. 2(4). Despite this, on June 22, 2025, the United States (“U.S.”) conducted its first act of military involvement in the conflict between Israel and Iran by striking three nuclear facilities in Iran.²See Elena Moore & Megan Pratz, U.S. Strikes 3 Nuclear Sites in Iran, in Major Regional Conflict Escalation, NPR (June 22, 2025, at 9:28 AM), https://www.npr.org/2025/06/21/nx-s1-5441127/iran-us-strike-nuclear-trump (describing U.S. involvement as a rapid escalation of conflict between Iran and Israel). The attack was conducted in response to lobbying efforts by Israel in the U.S., as President Netanyahu argued that Iran’s nuclear program posed risks for both Israel and the U.S.³ Id. President Trump’s objective was to destroy Iran’s nuclear capabilities to stop the alleged nuclear threat.⁴ Id. Therefore, the attack appears to be one of self-defense against Iran and the country’s nuclear facilities.  

Background  

Despite the prohibition on the use of force against another State, Article 51 of the U.N. Charter allows for the use of individual or collective self-defense if an armed attack occurs against a Member State.⁵U.N. Charter art. 51. For a State to invoke an action of self-defense, the State must have been victim of an armed attack and the subsequent attack must respect the principles of necessity and proportionality.⁶Military and Paramilitary Activities in and Against Nicaragua (Nicar. v. U.S.), Judgement, 1986 I.C.J. 14, ¶¶ 193–94 (June 27). Under international law, an “armed attack” can be shown through the scale and effects of an attack conducted by armed forces.⁷Id. ¶ 195.  

Since 1979, Iranian forces have conducted a number of attacks against the U.S. which have resulted in damages against U.S. military bases and the deaths of many Americans.⁸See Tzvi Kahn, Iranian and Iranian-Backed Attacks Against Americans (1979-Present), Found. for Def. Democracies (June 19, 2025), https://www.fdd.org/analysis/2025/06/19/iranian-and-iranian-backed-attacks-against-americans-1979-present (providing attacks by Iranian forces against the U.S. from 1979-present). While these attacks may be enough to show that the U.S. was able to use force against Iran, the attack in question was conducted against nuclear facilities that could possibly be used for a future attack.⁹See Moore & Pratz, supra note 1 (describing U.S. strikes against Iran nuclear facilities, June 22, 2025). Thus, this attack against Iran could be classified as a preemptive attack, which is not widely accepted to allow self-defense unless the possible attack is “ . . . instant, overwhelming, leaving no choice of means, and no moment for deliberation.”¹⁰See Hunter Miller, British-American Diplomacy The Caroline Case, Yale L. Sch.: Avalon Project, https://avalon.law.yale.edu/19th_century/br-1842d.asp (providing the materials of the “Caroline Case” with notes) (quoting Dan Webster’s letter to Lord Ashburn, Apr. 24, 1841). With the present facts, Iran has not been threatening to use its nuclear weapons to attack the U.S., nor was there any actual attack occurring when the U.S. dropped bombs destroying the nuclear facilities.11 Accordingly, the requirement of an armed attack cannot be met due to the preemptive nature of the strike against Iran. 

Analysis  

The principle of necessity requires that the act of self-defense is the last alternative and the necessity does not impair the obligations of the State.¹¹Responsibility of States for Internationally Wrongful Acts, Int’l L. Comm’n, Rep. on the Work of Its Fifty-Third Session, U.N. Doc. A/56/49, art. 26 (2001) [hereinafter ARSIWA] (codifying state responsibility and legal consequences for breaching international obligations).  In this case, diplomacy could have been used with a nuclear deal with Iran, replacing the Obama-era agreement abandoned by President Trump.¹²See Moore & Pratz, supra note 1 (discussing why U.S. conducted strikes against Iran despite President Trump initially seeking to negotiate new nuclear deal with Iran). However, despite initially seeking negotiation for a new nuclear deal, President Trump resorted to the use of force.¹³Id.  Furthermore, the argument for necessity will be difficult to justify because the most recent attempt at attacking U.S. forces failed due to the bombs being intercepted, meaning there was no actual attack.¹⁴See Bill Roggio & Joe Truzman, Iran-backed Militias Attack 3 U.S. Bases in Syria, Found. Def. Democracies’ Long War J. (June 18, 2025), https://www.longwarjournal.org/archives/2025/06/iran-backed-militias-attack-3-us-bases-in-syria.php (addressing Iran-backed militias attempt to attack U.S. bases in Syria).  Consequently, the principle of necessity cannot be met because diplomacy was a viable option, and there have been no recent successful attacks against the U.S.¹⁵Id.; see also Moore & Pratz, supra note 1 (addressing President Trump’s initial desire to create new nuclear deal with Iran).

The principle of proportionality requires that any countermeasures taken by a State be measurable to the injury suffered.¹⁶ARSIWA supra note 11.  Because the U.S. has suffered a number of attacks by Iranian forces on multiple occasions, the attacks against the nuclear facilities could be seen as proportional.¹⁷See Kahn, supra note 8 (providing Iran attacks against U.S. timeline).  While the attack conducted likely cannot be considered one of individual self-defense, there could be an argument that the attack was collective self-defense. Collective self-defense requires the same elements of individual self-defense but also that the State to benefited from the act to declare itself to be the victim of an armed attack and make a request to a third State for collective self-defense.¹⁸Nicar. v. U.S., 1986 I.C.J. ¶¶ 195-96.  However, an overarching issue in this regard is the lack of a formal request from Israel for collective self-defense.¹⁹See Barak Ravid, Israel Urges U.S. to Join War With Iran to Eliminate Nuclear Program, Axios: Pol. and Pol’y (June 14, 2025), https://www.axios.com/2025/06/14/israel-iran-war-us-nuclear-program-trump. Thus, unless it is proven that Israel formally requested aid for collective self-defense, the attacks made by the U.S. cannot be considered self-defense.²⁰See Nicar. v. U.S., 1986 I.C.J. ¶ 195.

Conclusion 

Given the failure to meet the requirements of self-defense, it may be presumed that the U.S. violated its obligations under the U.N. Charter’s prohibition on the use of force. Alternatively, the U.S.’ actions may be seen as an act of aggression against Iran.²¹ Rome Statute of the International Criminal Court art. 8(2), July 17, 1998.

If the strikes against Iran are acts of aggression, then the next steps would be holding the U.S. accountable. However, the International Criminal Court (“ICC”) is currently the only international tribunal with jurisdiction to prosecute for the crime of aggression and the U.S. is not under the jurisdiction of the ICC.²²Id. art. 5.  With no ICC jurisdiction to hold the U.S. accountable, despite the possible violation of international law, further research must be conducted to consider any actions of accountability for the attack. Some possibilities could include creating an ad hoc tribunal through a UN Security Council resolution or a hybrid-tribunal. Nevertheless, research will need to be conducted to understand the viability of these options and whether they could hold the U.S. accountable.