Khamenei killing puts limits of self-defence under UN Charter to the test

The Israeli and United States air strikes on Iran this weekend which killed its supreme leader Ayatollah Ali Khamenei have triggered debate on whether they represent a lawful exercise of anticipatory self-defence or a departure from the United Nations Charter’s limits on the use of force.

Iranian state television confirmed Khamenei was killed early on Saturday in an operation which has since widened into missile exchanges across the region. The strikes also killed at least 115 schoolchildren in the southern city of Minab, where a girls’ elementary school was hit during the broader aerial assault. Iranian authorities say more than 200 people have been killed nationwide and more than 700 wounded across 24 provinces. 

The scale of civilian harm has sharpened scrutiny of both the decision to use force and the conduct of specific strikes.

Israeli and US officials described the operation as pre-emptive, saying it was aimed at degrading imminent Iranian ballistic missile and nuclear threats. No detailed public evidence of imminence has been presented. The legal question is whether that justification satisfies Article 51 of the United Nations Charter.

At issue is whether the strike represents a lawful exercise of anticipatory self-defence or a departure from the Charter’s limits on the use of force.

Article 2(4) of the Charter prohibits the use of force against the territorial integrity or political independence of another state. The only recognised exception is self-defence in response to an armed attack. The dispute turns on how narrowly or broadly that exception is interpreted.

Anticipatory self-defence has traditionally been confined to situations where an armed attack is imminent in a strict sense, said Chris Gevers, an associate professor of international law at the University of the Witwatersrand.

“The requirement is not that a state has dangerous capabilities,” Gevers said. “It is that an armed attack is imminent. If imminence is stretched to include long-term or speculative threats, then the prohibition on the use of force weakens in practice.”

The threshold has historically been high and evidence-based, he added. “If capability alone is treated as sufficient, states effectively decide for themselves when the Charter constraints apply. That moves the system away from collective security.”

Article 51 was drafted to limit the circumstances in which force may be used, said 

professor Mahmoud Patel of the University of the Western Cape.

“Self-defence is triggered by an armed attack,” Patel said. “It is not a general authorisation to strike first because a state believes a threat may materialise in the future.”

Statements by Israeli Prime Minister Benjamin Netanyahu that the objective of the campaign was regime change complicate the legal assessment, Patel said.

“Self-defence must be directed at stopping or repelling an armed attack. If the stated aim extends to political transformation, that raises questions about necessity and proportionality,” he said.

Legal analyst Diana Buttu rejected the characterisation of the operation as pre-emptive.

“It’s called an illegal attack, not a pre-emptive attack,” she said, arguing that no public evidence has been presented of an imminent Iranian armed assault that would meet the Article 51 threshold.

The reported deaths of at least 115 schoolchildren in Minab have intensified scrutiny of the conduct of the strikes. Under international humanitarian law, parties to a conflict must distinguish between military objectives and civilian objects, and civilian harm must not be excessive in relation to the anticipated military advantage.

While legal debate gathered momentum, the military exchange widened.

Within an hour of the strikes on Tehran, Iran launched missiles toward Israel. Explosions were reported in Tel Aviv, Jerusalem and Haifa as air defence systems intercepted incoming projectiles. Israeli emergency services said dozens were treated for minor injuries.

Tehran expanded its response beyond Israeli territory. Missiles and drones were directed at US-linked military installations across the Gulf, with reported strikes near facilities in Bahrain, Qatar, Kuwait and the United Arab Emirates. Several states closed or restricted their airspace as flights were diverted.

Iran’s Foreign Ministry described the Israeli-US operation as a declaration of war.

The escalation followed stalled diplomacy. Indirect negotiations between Washington and Tehran, mediated by Oman, had been under way. On Friday evening, Oman’s foreign minister said a peace deal was “within our reach”. Hours later, the air strikes began.

As the exchange intensified, Iran moved to close the Strait of Hormuz, halting commercial transit through one of the world’s most important energy corridors. The strait carries roughly one fifth of global oil supply and a significant share of liquefied natural gas exports from Gulf producers. Energy benchmarks rose sharply as traders assessed the likelihood of sustained disruption.

Insurance premiums for vessels transiting the Gulf increased. Shipping operators recalculated risk exposure and some charter contracts were paused pending security assessments. For import-dependent economies, prolonged disruption would translate into higher fuel costs and broader inflationary pressure.

President Cyril Ramaphosa reiterated that anticipatory self-defence is not permitted under international law and called for renewed diplomatic efforts. The African Union warned that further escalation threatens global stability and carries implications for energy markets and food security.

At the United Nations, Iran’s ambassador described the strikes as a war crime. An emergency session of the Security Council convened as member states debated the legality of the operation and the risks of wider conflict.

The killing of Khamenei introduces further uncertainty. As Supreme Leader, he held ultimate authority over Iran’s military and strategic decisions. His death raises questions about succession, command continuity and internal stability at a moment of external attack.

Israel has continued additional strikes on missile and air defence sites in central Iran. Tehran signalled that further retaliation would follow, warning that any additional strikes would be met with a “much stronger” response.

How governments interpret the self-defence claim may shape more than the trajectory of this conflict. If the threshold for imminence is broadened, the space for unilateral force expands in practice. If it remains narrow and evidence-based, the constraints embedded in Article 51 endure.

The confrontation now tests not only regional stability, but the boundaries of lawful force under the Charter system.