The Best Available Self-Defense: Article 51 and the 2026 Iran War

[Davit Khachatryan is a lecturer at American University of Armenia and Russian-Armenian University]

There is something almost ritualistic about restating the law of self-defense. Article 51 has been parsed, contested, stretched, and invoked in nearly every major armed conflict since 1945. Few provisions of international law are at once so settled in principle and so contested in application. Yet the war between Iran on one side and the United States and Israel on the other has done something to the doctrine that the familiar debates about its scope do not capture.

The Charter’s default is prohibition. Article 2(4) is a rule of jus contra bellum. The maintenance of international peace and security is entrusted to the Security Council acting for the collectivity. Against that default, self-defense is the single natural escape, and the Charter admits it narrowly. The right is hedged by necessity, proportionality and immediacy, the Caroline conditions absorbed into the Article 51 framework, and it is above all provisional. It runs only until the Council has taken the measures necessary to restore peace, at which point the individual right yields to the collective organ. Self-defense in this conception is disciplined to the point of being almost chivalric: a holding action, exercised on trust, until the custodian of the global interest arrives to take the matter in hand.

That is the concept the ritual maintains. What the 2026 war reveals is that neither belligerent is fighting the disciplined, provisional, other-regarding war. Both are doing something older, and this piece argues that the something older has quietly become the operative category, while the Charter version survives only as vocabulary.

Lawful Response

The war opened on 28 February 2026 with close to nine hundred strikes in twelve hours across Iranian territory, killing the Supreme Leader and much of the senior military command, in an operation American officials described as major combat operations and justified as anticipatory self-defense against a nuclear programme. That justification asks the Charter to accommodate a preventive self-defense doctrine it has never accommodated. The strikes were a use of force against the territorial integrity and political independence of another state, and the Definition of Aggression identifies conduct of this kind, at its gravest, as a crime against international peace. The gravity threshold the International Court of Justice (ICJ) set in Nicaragua for an armed attack (para 195) is plainly crossed.

Iran’s immediate response against Israeli military installations and against United States forces in the region therefore began inside Article 51, and Iran said so, telling the Security Council that the aggression met none of the criteria of lawful self-defense and that it would exercise the same right. Washington had filed its own Article 51 letter in the opening days. Two states, two invocations of the same provision, and at the outset one of them was right: there is no right to defend against an act of self-defense, and force used by an aggressor to repel the victim’s response continues the original wrong. Had the war stopped there, it would have been an ordinary, if grave, Article 51 case. It did not stop there.

The Custodian Does Not Come

The provisional character of self-defense depends on a promise: that the Council will arrive, identify aggressor and victim, and assume the burden the defending state was only holding.

On 11 March the Council adopted resolution 2817 (2026) by thirteen votes to none, China and the Russian Federation abstaining, demanding that Iran cease attacks against Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, the United Arab Emirates and Jordan. It said nothing about 28 February. Iran’s representative called the text a manifest injustice against the principal victim of aggression, and on that point the objection is sound: the asymmetry is the familiar work of the veto rather than a finding that the original strikes were lawful. The organ meant to name aggressor and victim named only one, and named it wrongly.

The reason is fatal to the doctrine. The United States is a permanent member exercising the veto while itself using illegal force, and it shares the bench with four others, each entangled by its own interests and armed with the same veto. When the holder of the collective interest is a party to the conflict, the provisional structure of Article 51 has nothing to be provisional toward. What remains available to a state in that position is not the disciplined right of Article 51. It is self-help: the older, unmediated defense of one’s own interests, exercised because no one will exercise it on the collectivity’s behalf. The rest of this war is the working out of that reversion, and it is visible in four episodes.

The Wrong Targets

Self-defense runs against the author of the armed attack. Oil Platforms requires a state invoking Article 51 to identify the specific attacks and show the target’s connection to them (paras 51, 61, 72). Iranian missiles aimed at Al Udeid in Qatar, at the Fifth Fleet headquarters in Bahrain and at Al Dhafra in the UAE struck United States military objectives, and their legality turns on precautions owed to the host population. Iranian drones striking the Habshan gas complex in Abu Dhabi, a Saudi pipeline, facilities in Kuwait and a hotel in Dubai are different. No theory of self-defense reaches the territory of states that did not attack Iran. As a defensive matter, the strikes are indefensible.

The Tolled Strait

Iran closed the Strait of Hormuz in early March and laid mines it now appears unable to locate; the International Maritime Organization has recorded twenty-one attacks on non-belligerent merchant ships. The ICJ in Corfu Channel fixed the duty to notify shipping of a known minefield in elementary considerations of humanity (Merits, 22); Nicaragua treated unnotified mining as an unlawful use of force and a breach of maritime commerce (paras 80, 215, 292(8)); Hague Convention VIII requires the same precautions by treaty. None of it is suspended because the mining state was itself attacked. During the April ceasefire, Iran permitted passage along a coordinated route while charging reported fees in the millions per vessel, a jurisdiction the Law of the Sea Convention denies to strait states, which may not hamper or suspend transit passage (Articles 38 and 44). Charging for passage is not a defense; it is the monetisation of a chokepoint, coercion of third states priced by the vessel.

The Blockade

The United States announced a blockade of Iranian ports on 13 April, hours after the Islamabad talks collapsed. The commentary has measured it against the San Remo conditions and against the crowd of naval operations now in the Gulf, and those conditions matter, but they answer a different question. Blockade is a belligerent act; conducting it lawfully is not the same as lawfully resorting to it, a distinction the enforcement against neutral shipping has made hard to miss. The blockade was imposed because a negotiation failed, retained in April as pressure, and now sits on the table as the concession Washington would trade for a reopened strait. Necessity in self-defense is measured against halting an attack. Leverage in a bargain is a different object, pursued by force, which is what Article 2(4) forbids.

The Breach Treated as an Attack

A ceasefire took effect on 8 April and was extended indefinitely on 21 April; terms for a sixty-day cessation were agreed on 12 June; the two presidents signed a memorandum on 17 June. On 7 July, Iranian forces struck three tankers off Musandam, and the United States bombed Iran the same night and declared the ceasefire over, the President later calling the instrument a test Iran had failed. A ceasefire ends the armed attack for Article 51 purposes, so immediacy can no longer be satisfied by reference to February, and force months later requires a fresh armed attack. A breach of a ceasefire or memorandum is a breach of an undertaking, engaging state responsibility and the law of treaties, whose responses stop at non-forcible countermeasures (Articles on State Responsibility, art 50(1)(a)). Force answering a completed breach rather than an ongoing attack is a reprisal, and armed reprisals are prohibited (Nuclear Weapons, para 46). The move is symmetrical: Iranian strikes on Israel answering Israeli operations in Lebanon, conducted beside a parallel negotiation with Beirut, meet the identical objection. Each side treats the other’s breach as authority, which is to say each has replaced the defensive claim with a bare assertion of its right to answer injury as it sees fit.

Two Concepts, One Name

Read together, the four episodes are evidence that the provision has stopped describing the war. Nothing in the conduct on either side is disciplined by necessity, proportionality and immediacy; nothing is provisional, because there is no custodian to be provisional toward; nothing is other-regarding, because the collective organ that made self-defense other-regarding is itself a combatant.

Call it the best available self-defense: subjective, unqualified, sovereignty-first, the defense of the self and its interests undertaken because the global alternative has failed or turned hostile. It is, in a sense, the honest one. Faced with an armed attack, a closed strait, a blocked Council and an adversary who is also the system’s custodian, a state defends what it can with what it has. The impulse is understandable, and in the face of a threat to existence and to grave national interests it is perhaps even reasonable. But it is not the right the Charter conferred. Article 51 exists precisely to attach conditions to that impulse and to bind it to a collective order.

This is not a defense of self-help. The claim is diagnostic, not normative. The best available self-defense is not lawful, and describing its logic is not endorsing it. The point is that this, and not the disciplined Article 51 right, is what the belligerents are actually reasoning with. The structure meant to keep them inside the disciplined right has collapsed at its centre.

Settlement

Iran and Oman are negotiating a regime for the Strait under which vessels would enter the Gulf by an Iranian route and leave by an Omani one, against fees for security and environmental protection, conditional on the United States lifting its blockade; earlier in the war the administration floated a share of the proceeds.

Article 52 of the Vienna Convention voids a treaty procured by the threat or use of force in violation of the Charter, and whatever these instruments are called, they are being negotiated under continuing armed coercion by both sides, their content tracking what force has produced: a strait Iran can close and a blockade the United States can hold. Transit passage belongs to all states; two littorals cannot divide and price it between themselves. The shipping states that bore the closure and the Gulf states whose infrastructure was struck are not at the table. The non-recognition duty in Article 41(2) of the Articles on State Responsibility can be extended to entitlements, because a fee regime born of mining and coercion will be very hard to unwind once accepted in practice.

How the Rule Dies

International law survives being broken. What it does not survive is being redefined by the states that invoke it, until self-defense means whatever a government believes its grievance entitles it to do. Whatever the speeches say about civilisation, nuclear peril and the destiny of a region, the conduct reads as rough national and commercial interest. 

More than half a century ago, it was asked who killed Article 2(4). This war suggests a quieter and less answerable ending. The prohibition is not being killed in a contest of visions; it is being spent, transactionally, in the ordinary course of business. There will be no ceremony at which Article 2(4) is pronounced dead. If there is an onus in this, it falls first on the states that opened the war, and heaviest on the one bestowed a permanent seat and holding the greater share of accumulated might. 

The arrangement now assembled in the Strait of Hormuz is simply a routine instalment. Should its terms stand as the legal position, the strongest guarantee of freedom of navigation will be a willingness to pay whoever mined the water. A rule dies this way, quietly and on commercial terms, with each state defending only itself because it has concluded, not without reason, that no one else will. 

Photo attribution: Photo by Abolhassan Neghabi on Unsplash