Striking first: when is a preventive strike really legal - Iran, US and Israel

On the 27th February 2026, the United States and Israel launched a series of coordinated military strikes onto Iranian territory aimed at further destabilizing Iran's military infrastructure. The targets included air-defense batteries, missile facilities and multiple sites linked to nuclear activity such as installations near Natanz. In the following hours both Donald Trump and Netanyhu described these operations as indispensable and carefully conducted acts of “ preventive self-defense” against the seemingly increasing threats of Iranian missile strikes. In turn. Iran quickly denounced the strikes as blatant and gross violations of both its sovereignty and the UN Charter, warning that it would retaliate and respond accordingly.

These events alongside plenty of images of burning military sites and smoke resurfaced an age-old yet increasingly relevant question: when, if ever, is a preventive strike really legal?

Under the UN charter, specifically art.2(4), countries are bound by an absolute prohibition on the use of force against another state and its territory. Whilst worded and regarded in absolute terms, there is one clear and necessary exception - self- defence whereby a state may employ force to repel an imminent armed attack. In practice, even this invocation is strictly regulated under the canons of necessity and proportionality and must only be in response to a real and immediate threat - although the understanding of armed attack is subject to continuing debate. Many legal scholars and international experts stress that self-defense is not a license to act upon hypothetical threats or strategic ambitions but rather is a narrow, crisis-dependent remedy.

Therefore when both the US and Israel engage in so-called “preventive” strikes, they actively extend the notion of self-defence beyond its literal codifications. A preventative strike by nature is aimed at preempting a threat that has not yet materialised - thus not capable of being classified as imminent in the classical sense. Such actions risk blurring the boundaries of what is considered legally permissible. For governments, international experts and the law itself, the distinction between “imminent” and "preventive" are not just simple semantics. If states begin to commonly engage the use of force to prevent hypothetical or future threats, it risks not only a surge of forceful actions but threatens to erode the very core of the UN charter: that force shall remain the exception in foreign policy.

This risk is mirrored by international law experts, UN officials and several foreign ministers that all communicate that such “ preventive” self-defence is not formally recognised under the UN Charter and is therefore widely regarded as unlawful. Continuous reference is made to the hallmark 1986 Nicaragua case, in which ICJ judges underlined that self-defence is directly linked to an actual armed attack. The strikes also echo the 2002-2003 debates surrounding the US invasion of Iraq, which in retrospect was largely condemned as a “preventive war” and effectively weakened the credibility of the Charter and the

international legal order.

Against this background, the recent Iran strikes paint an increasingly concerning image to many experts. Whilst US-Israeli intelligence presented information about planned Iranian attacks, none of these were proven to be readily materialising thereby making it difficult to frame these strikes as self-defense but rather as a preventive campaign - thus sitting well outside the classic orthodoxy of international law.

Beyond the legal concerns, these events carry with them a concerning political angle: if powerful states routinely justify such “preventive” strikes, smaller states may feel pressured to adopt the same language, resulting in a framework where the prohibition on the use of force is quietly replaced by a puzzle of competing self-defense claims. Unsurprisingly, the international reaction is largely divided. Following the strikes on the 27th February the Secretary-General warned of a potential wider regional war, stressing the strict limits of the Charters. Similarly UN human rights and international law experts, add that whilst

nuclear-related sites are, in large, of military nature, their targeting still raises questions under the law of armed conflict and relevant obligations to protecting the environment. Conversely, whilst many western governments, most notably Germany Chancellor Friedrich Merz, focus on the “necessary” de-escalation argument, others quietly signal to the underlying illegality of “preventive” strikes, reflecting a mix of political caution and legal discomfort.

On the Iranian side, officials use language of “aggression” and “war crimes” in an attempt to garner both domestic support and appeal to international-law based forums such as the UN Human Rights Council. Iranian officials argue that these strikes cement their long-standing perspective of being unlawfully targeted Western powers accusing them of claiming to uphold international law whilst bypassing its delineations when politically convenient.

Whilst for many these strikes seem like a distant abstract conflict, legal debates allude to a much older and far-reaching question: how to balance security against the rule of law.

As previously noted, the normalisation of military acts under the label of “preventive” use of force risks encourages other states to cite similar justifications in other political conflicts. Already now, several othercountries in the Middle East such as the UAE and Qatar but also regional players such as Turkey and Pakistan have increasingly invested into their missile and drone reservoirs. The more the international community sees powerful global players freely use force to target foreign infrastructure, the more tempting and feasible such pathways appear.

Nevertheless, the strong reactions from UN officials and other states reflect the otherwise strong consensus around the necessity and absolute character of the prohibition on the use of force. The way these strikes will be remembered, either as justified exceptions or as illegal and dangerous precedents, will certainly shape the next decade of international conflicts.

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Cover image:

John Samuel, “United Nations Headquarters, Geneva”, via Wikimedia Commons, licensed under CC BY-SA 4.0.