On 28 February 2026, the United States and Israel assassinated the supreme leader of Iran, Ali Khamenei. The joint operation marked the first time either state has directly killed a sitting head of state. As with the US’s January 2026 operation against Nicolás Maduro, what stands out is not only the gravity of the act but the manner in which it was justified. Public statements emphasised Khamenei’s record and the sophistication of US-Israeli intelligence cooperation, but they did not articulate a credible legal basis for the strike.

Khamenei’s assassination represents a new stage in the erosion of the international norm against assassination. This norm has long been understood as part of a broader framework protecting sovereignty and prohibiting the use of force outside armed conflict. Under international law, the killing of a state official outside an armed conflict will almost invariably violate the prohibition on the use of force, state sovereignty, and/or international human rights law. In an influential piece written two decades ago, Ward Thomas observed that “the directly targeted killing of foreign adversaries, once rejected as beyond the pale, has become a prominent issue in debates over U.S. security policy”. For Thomas, the shortsighted policies driving the US’s so-called “global war on terror” were undermining the norm and risked spilling over to justify the killing of state officials. Yet, in 2005, he wrote with some relief that “the word ‘assassination’ itself still carries a considerable stigma”. In the wake of Khamenei’s assassination, this statement no longer seems to hold true.

Since the early 2000s, the gradual normalisation of state-sponsored assassination has lessened the stigma attached to the practice to the point that assassinating a sitting head of state without any legal justification has now become a reality. While the international norm against assassination may not yet be fully dead, its recent trajectory offers little hope for its restoration.

A gradual normalisation of assassination

The norm’s erosion was already visible in the January 2020 killing of Qassem Soleimani. The Trump administration initially invoked self-defence and imminence, before shifting to claims that Soleimani had “American blood on his hands”. International reactions were limited: a joint statement by France, Germany, and the United Kingdom focused on regional stability without directly condemning (or indeed mentioning) the killing. Subsequent cases reinforced this pattern. The Biden administration justified the 2022 killing of Ayman al-Zawahiri with the assertion that “justice has been delivered”, without any articulation of its compatibility with international law.

This apparent normalisation of assassination as a tool of statecraft rests on two interrelated mechanisms: routinisation and legitimation. Prior to the attacks of 11 September 2001, the United States was a vocal critic of Israel’s practice of assassinating Palestinian activists. After 9/11, however, it quickly adopted the practice and slowly began to legitimate it. With the US adoption of the practice, now strategically renamed “targeted killings”, assassination became increasingly routinised as a tool of statecraft.

Today, both democratic and authoritarian states employ it, and targets have expanded beyond suspected terrorists to include scientists, political opponents, bloggers, journalists, state officials, and sitting heads of state during armed conflict. Alongside covert poisoning and car bombs, methods have evolved to include drone strikes and AI-assisted targeting. The practice now spans objectives of counterterrorism, deterrence, regime security, and strategic signalling. What was once treated as an exceptional and contested measure has been bureaucratised and normalised as a tool of policy within self-proclaimed liberal democracies such as the United States and Israel. The definitional move from “assassination” to “targeted killing” facilitated this process by situating such operations within the vocabulary of armed conflict after 9/11.

In parallel, legitimation has become possible through a reinterpretation of the applicable legal framework. Since the early 2000s, the United States and Israel have been more vocal in advancing expansive readings of self-defence, imminence, and the existence of non-international armed conflicts beyond traditional battlefields to justify targeting individuals that could not be regarded as lawful targets under stricter legal interpretations. The lack of strong condemnation by other states allowed the legal justifications, however implausible, to provide a precedent for further action.

As this effort at legal justification provided a veneer of legitimacy for the routinised assassination of suspected terrorists, it became increasingly easy to rely on the newfound legitimacy of the practice to assassinate other “enemies of the state”, such as nuclear scientists or state officials like Soleimani, as well as to abandon legal justification altogether, as for al-Zawahiri.

The assassination of Khamenei as a rupture

The assassination of Ali Khamenei differs from the killings of the past two decades insofar as sitting heads of state have historically occupied a distinct normative category. As explained by Thomas, as early as the seventeenth century, “a complex combination of material and ideational factors contributed to the rise of the norm against assassinating foreign leaders” in wartime and, a fortiori, in peacetime. Even when states plotted against foreign leaders during the Cold War (for instance, the US repeatedly attempted to assassinate Fidel Castro), they always did so covertly and rarely acknowledged responsibility when exposed. In later decades, when the US targeted foreign leaders such as Muammar Gaddafi and Saddam Hussein, it was careful to claim that their deaths would have been an inadvertent consequence of a strike undertaken in self-defence. Such was the stigma against targeting heads of state that, as late as 2022, some authors argued that the norm erosion triggered by targeted killings would remain “compartmentalised” to the targeting of non-state actors.

It must therefore be emphasised that the US-Israeli strike of 28 February 2026 deliberately targeted and killed the sitting head of state of a sovereign state. In addition, Khamenei’s killing was publicly embraced, and its justification was framed in moral rather than legal terms.

Despite repeated violations of the international norm against assassination, its resilience depended on states either concealing their involvement or defending their conduct through appeals to legal exemptions such as self-defence or combatant status. Both practices signalled that assassination remained normatively problematic in the international order.

When assassination is openly acknowledged and only minimally justified in legal terms, as was recently the case with Soleimani, al-Zawahiri, Haniyeh, or Nasrallah, that signal weakens. The threshold then shifts from whether the act can be legally justified to whether the target is sufficiently “bad” to warrant elimination. Whether the targets of recent assassinations “deserved” their fate is, however, less important than the implication of this shift from legality to morality for the international order. While legal arguments can be rebutted, moral claims about worthiness are less susceptible to meaningful contestation.

Alongside Jeremy Waldron, one may therefore begin to ask:“Do we want [assassination] to become a permanent capability available in principle to any of the 192 [now 195] sovereign states in the world that think of themselves as having particular persons as enemies?”

Is the international norm against assassination dead?

The systemic effects of recent assassinations, from drone strikes in Yemen to the assassinations of Soleimani and Nasrallah, are cumulative. Each muted reaction by states that style themselves as the guardians of the “international rule-based order” lowers the political cost of the next strike; each public acknowledgement unaccompanied by legal argument lowers the justificatory threshold for other states and future assassinations. Combined with the widespread availability of drone and long-range strike technologies, assassination becomes both politically easier to defend and materially easier to replicate. As a result, the practice of state-sponsored assassination, which once required covert modalities and plausible deniability, is increasingly conducted openly.

This does not mean that the norm is formally extinguished. Even under the most expansive readings of international law, as advocated by the US and Israel in recent decades, the “targeted killing” of a state official outside an armed conflict still violates the prohibition on the use of force, state sovereignty, and international human rights law. Many states continue to denounce assassination when they consider themselves as victims, and legal scholarship remains largely sceptical of expansive doctrines of imminence or “globalised armed conflict” that would render such killings lawful.

The more difficult question is whether the norm still meaningfully constrains powerful states. Norms do not disappear simply because they are violated. They erode when violations become routine, when justificatory standards decline, and when adverse reactions diminish. The 28 February 2026 assassination of Ali Khamenei features as the culmination of these three dynamics. It suggests that, at least for some states, assassination has moved from a covert and contested practice to an overt, politically defensible, and even desirable instrument of policy.

Should other states emulate this model, and should international responses remain muted, the norm will continue to hollow out. Conversely, sustained contestation, coordinated sanctions, and renewed insistence on legal justification could restore its constraining force. As such, whether the norm against assassination will effectively disappear depends less on the existence of prohibitive rules than on future practice.

Reactions by other states to Khamenei’s assassination will be decisive for the norm’s future trajectory. At present, however, that trajectory points much less toward a restoration of the stigma than toward a full normalisation of assassination as a tool of statecraft.

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