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Iran war: The legality, or illegality, of killing a foreign leader, explained

March 03, 2026 7 min read International Relations GS2 (International Relations International Law Bilateral Agreements)
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What Happened

  • Reports emerged that Israeli operations during the February 28, 2026 strikes on Tehran included targeting Iran's Supreme Leader Ali Khamenei, who was reportedly killed — raising urgent international legal questions about whether killing a foreign head of state or supreme leader is permissible under international law.
  • The question is not merely academic: the legal framework governing such acts determines whether the striking state can claim lawful belligerency, whether surviving officials retain diplomatic immunity, and whether the act constitutes an assassination under international law.
  • Israeli officials framed the targeting of the Assembly of Experts on March 3 — the body electing Khamenei's successor — as a continuation of the same military objective.
  • The issue intersects multiple domains of international law: the prohibition on assassination of heads of state (customary law), the law of armed conflict (jus in bello), the UN Charter's prohibition on force (jus ad bellum), and diplomatic/heads-of-state immunity.

Static Topic Bridges

The prohibition on the assassination of foreign heads of state has deep roots in the Westphalian system of sovereign states (1648 onwards), which established the principle that states' security must be guaranteed and that their representatives hold a special protected status. In peacetime, the prohibition is near-absolute. During armed conflict, the legal position is more nuanced but still significantly constrained.

  • The Convention on the Prevention and Punishment of Crimes against Internationally Protected Persons (New York Convention, 1973) criminalises attacks on heads of state, heads of government, foreign ministers, and their family members — even during peacetime.
  • "Internationally Protected Persons" (IPPs) under the 1973 Convention include any head of state, any member of a collegial body performing head-of-state functions, and any head of government.
  • Article 2 of the 1973 Convention requires states to criminalise murder, kidnapping, and attacks on IPPs and to either prosecute or extradite perpetrators ("aut dedere aut judicare").
  • The prohibition on assassination of foreign leaders in US domestic law was established by Executive Order 11905 (Ford, 1976), later continued as Executive Order 12333 (Reagan, 1981) — though subsequent administrations have interpreted this narrowly to exclude wartime targeted killings.
  • The norm against state-sponsored assassination is considered a jus cogens norm — a peremptory norm of international law from which no derogation is permitted.

Connection to this news: Iran's Supreme Leader is both a constitutional head of state (under the Iranian Constitution, the Supreme Leader is above the President and Commander-in-Chief) and an internationally protected person under the 1973 Convention. The legal question is whether the existence of an armed conflict between Israel and Iran alters this protected status.

Targeted Killing Under the Law of Armed Conflict (LOAC)

The law of armed conflict (also called international humanitarian law, or IHL) governs how parties may conduct hostilities. During an armed conflict, the deliberate targeting of an enemy commander or political leader is not per se unlawful — the principle of distinction holds that military objectives (including military command structures) are lawful targets, while civilians and civilian objects may not be directly targeted.

  • The Hague Regulations of 1907 (annexed to the Fourth Hague Convention) prohibit "assassination" in the sense of treacherous or perfidious killing — but do not prohibit direct combat attack on enemy leadership.
  • Article 37 of Additional Protocol I (1977) prohibits "perfidy" — feigning civilian status, using a flag of truce, or disguising oneself as a non-combatant to kill — but not open military attack on lawful targets.
  • The US legal framework for targeted killing (developed post-9/11) distinguishes between lawful targeted killing in armed conflict (governed by LOAC) and unlawful assassination in peacetime (prohibited by Executive Order 12333 and the 1973 Convention).
  • The US Department of Justice's 2010 memorandum on targeted killing concluded that a US citizen who was an operational leader of an enemy force was a lawful military target — a principle extended to foreign nationals.
  • The ICJ's Nicaragua v. US (1986) and Congo v. Uganda (2005) rulings affirmed that even in armed conflict, proportionality and distinction apply and cannot justify attacks that are indiscriminate or disproportionate to military advantage.

Connection to this news: The legality of targeting Khamenei during an active armed conflict between Israel and Iran turns on whether the conflict itself was lawfully initiated (jus ad bellum) and whether the targeting complied with IHL principles — particularly whether Khamenei's role as supreme commander of Iran's armed forces made him a lawful military target.

State Sovereignty and Non-Intervention in International Law

The principle of state sovereignty — the supreme authority of a state within its territorial boundaries — is the foundational principle of the international system. Non-intervention is its corollary: states may not interfere in the internal affairs of another state, including through acts intended to change its government or political leadership.

  • UN General Assembly Resolution 2131 (1965), the Declaration on the Inadmissibility of Intervention in the Domestic Affairs of States, explicitly prohibits states from organising or supporting subversion or armed action aimed at overthrowing the government of another state.
  • UN General Assembly Resolution 3314 (1974), the Definition of Aggression, identifies "acts of aggression" including armed attacks by one state on the territory of another — aggression being the most serious form of the unlawful use of force.
  • The ICJ held in Nicaragua v. US (1986) that support for armed groups aimed at overthrowing a government violated the principle of non-intervention, which is part of customary international law binding on all states.
  • The Responsibility to Protect (R2P) doctrine, adopted at the 2005 UN World Summit, allows the international community to intervene when a state manifestly fails to protect its population from genocide, war crimes, ethnic cleansing, or crimes against humanity — but this has never been interpreted to justify regime change or leadership targeting.
  • R2P was invoked in Libya (2011) under UNSC Resolution 1973, but NATO's execution — which extended to supporting regime change — was seen by Russia, China, and India as a violation of the original mandate.

Connection to this news: The targeting of Khamenei and efforts to prevent Iran from selecting a new Supreme Leader (by striking the Assembly of Experts) represent the most explicit attempt at externally-imposed leadership decapitation in the post-WWII era, raising fundamental questions about the continued viability of the non-intervention principle.

Heads-of-State Immunity Under International Law

Sitting heads of state enjoy absolute immunity from criminal jurisdiction in foreign courts under customary international law. This immunity is personal and status-based: it exists as long as the individual holds office. The rationale is functional — effective state representation and diplomacy require that foreign officials be able to travel and conduct diplomacy without fear of arrest.

  • The ICJ Arrest Warrant Case (Congo v. Belgium, 2002) held that a sitting foreign minister enjoyed absolute immunity from criminal jurisdiction abroad — including for alleged war crimes and crimes against humanity — while in office.
  • The International Criminal Court (ICC) Statute does not recognise immunity for heads of state (Article 27), but this only applies to ICC proceedings, not to the actions of other states.
  • Customary international law on immunity distinguishes between: immunity ratione personae (personal immunity of heads of state, heads of government, foreign ministers — absolute while in office) and immunity ratione materiae (functional immunity for official acts — survives the end of tenure but covers only official acts).
  • The killing of a foreign head of state by military action is distinct from criminal prosecution: IHL governs the former, ICJ immunity doctrine governs the latter.

Connection to this news: Even within a declared armed conflict, the deliberate targeting of a foreign head of state is unprecedented in the modern era and raises layered questions across multiple legal frameworks simultaneously — none of which clearly authorises such an act.

Key Facts & Data

  • New York Convention on Internationally Protected Persons: adopted 1973; covers heads of state, government, and foreign ministers
  • Hague Regulations 1907: prohibit perfidy/assassination but not direct combat targeting of enemy commanders
  • Additional Protocol I, Article 37 (1977): prohibits perfidy; Article 43: defines lawful combatants and military objectives
  • US Executive Order 12333 (Reagan, 1981): prohibits US personnel from engaging in or conspiring in assassination
  • ICJ Congo v. Belgium (Arrest Warrant Case, 2002): sitting foreign ministers have absolute immunity while in office
  • ICJ Nicaragua v. US (1986): non-intervention in customary international law
  • UN General Assembly Resolution 3314 (1974): Definition of Aggression
  • R2P adopted at 2005 UN World Summit; invoked in Libya under UNSC Resolution 1973 (2011)
  • ICC Statute Article 27: no immunity for heads of state in ICC proceedings
  • Iran's Supreme Leader: constitutional Commander-in-Chief; above the President in hierarchy under Iran's 1979 Constitution