The commencement of Israel’s military offensive against Iran, focused on Iran’s nuclear program, has given rise to a resurgence of discourse surrounding the boundaries of the right of self-defence under international law. According to Israel’s prime minister Netanyahu and the letter to the UNSC, the attack was the last option to counter the existential threat to the survival of the Israeli state posed by Iran arising from the possibility to acquire nuclear strike capability. This action, given the assumption, that it was undertaken under the guise of self-defence, is a violation of international law.
Another view sees the appropriate legal framework not in the right of self-defence, but rather classifies the Israeli attacks as part of an ongoing armed conflict. Notwithstanding the potential, that the letter to the UNSC can be interpreted in this manner, it is not evident, that this is the case. Israel asserts its right of self-defence in a relatively ‘natural’ manner in public declarations, such as those made by Netanyahu, and also in parts of the aforementioned letter. This assertion of invoking self-defence as justification is evidenced, for instance, by the part of the letter to the UNSC that states the attack was the ‘last window of opportunity’ after diplomacy had been unsuccessful; a wording similar to that used in the context of preventive acts of self-defence. Furthermore, the diplomatic efforts were not aimed at ending an ongoing armed conflict, but rather at containing the Iranian nuclear weapons program as a further threat. The justification for the attacks that have taken place since 13 June with the aim of destroying the Iranian nuclear program is difficult to objectively assess as a further act in an assumed ongoing armed conflict, since these new qualitative attacks are primarily not intended to ward off the attacks that have already taken place (through Iran’s proxies) in the sense of military necessity that characterises proportionality.
Therefore, not only is there evidence of a qualitative transgression of the boundaries of the right of self-defence through the Israeli actions, as was evidenced by the threat for the residents in Tehran, but also a temporal one:
The right of self-defence
The individual and collective right of self-defence is mentioned in Art. 51 UN-Charter and also recognised as customary international law.
It is seen as a legitimate right of response to restore one’s own sovereignty and security ‘if an armed attack occurs’. This formulation is deliberately narrow so that not every minor hostile border incident or mere hostile intention should trigger the unilateral right of self-defence. This is also due to the fact that this right is one of the few exceptions of the general prohibition of the use of force in the Art. 2 (4) UN-Charter. This strict requirement of the existence of an armed attack is also applied in customary international law – as decided by the ICJ in various cases (ICJ Advisory Opinion on the threat of use of nuclear weapons, Nicaragua Case and Oil Platform Case).
The temporal threshold for the right of self-defence
The decisive factor in terms of time and quality for triggering the right of self-defence is an actual, objective manifested armed attack.
It is not completely predetermined at what point in time such an armed attack can be categorised as occurring, if the attack is not currently taking place.
According to (not undisputed) customary international law, defence measures in the sense of preventive action are permissible but only if the armed attack is imminent – a ‘point of no return’ must have been passed or reached. It is in these cases more a question of chance whether the preventive act of defence or the imminent attack takes effect first.
In the absence of an occurring specific attack or an imminent attack by Iran on Israel, Israel is not able to invoke a preventive act of defence under international law (see also Payandeh).
Although Iran has already produced 400kg of uranium with an enrichment level of 60% and thus potentially has the material for around 9 nuclear weapons if further enrichment takes place, Iran still needs to enrich the uranium to around 90% and to show the willingness to use them against Israel and not only in a defensive manner.
Pre-emptive self-defence as a dissolution to the right of self-defence
Furthermore, the temporal threshold requirement for the occurrence of an armed attack cannot be further extended to encompass pre-emptive self-defence. A pre-emptive self-defence act intends to deter non-imminent threats, whose existence and timing are uncertain and could manifest at an unknown point in the distant future, but a self-perceived threat situation has already been identified as guiding action. While the aforementioned preventive self-defence is often recognised in customary international law, this does not apply to pre-emptive self-defence (e.g. UK statement). The prevailing international legal framework does not currently recognise such a defence against potential future threats in the form of the right of self-defence – not even regarding the acquiring of nuclear strike capability. The US’s view, set out in the Bush-Doctrine on the US’s War on Terror, considering pre-emptive action to be permissible against states under the guise of self-defence, has not been uniformly accepted by the international community.
While the existential threat to Israel from a nuclear-armed Iran cannot be underestimated, the mere prospect of Iran acquiring nuclear strike capability does not inherently constitute a justification for the exercise of the right of self-defence: in the absence of imminent use of (nuclear) force, the demonstration of a concrete nuclear strike capability, or a discernible escalation dynamic with an attack that can be expected in the shortest possible time. Evidence of this phenomenon can be found in the condemnation of Israel’s bombardment of a Iraqi nuclear reactor as a violation of the UN-Charter. This condemnation was made despite a possible threat posed to Israel if Saddam Hussein’s would have acquired nuclear strike capability. Therefore, the mere possibility of acquiring such WMDs, in the absence of an actual threat of use, does not constitute an armed attack.
Reshaping the UN-Charter
The Israeli attacks evince a congruence in the conceptualisations of the right of self-defence, aligning with the precepts established in the Bush-Doctrine. In view of the fact that, according to publicly available information, a nuclear attack was not imminent, Israel is claiming pre-emptive self-defence in this Bush-Doctrine-manner – shown by the statements of Netanyahu and the IDF. The letter to the UNSC also states that ‘Israel is acting to defend its security and very existence’ and that Operation Rising Lion was taken as a ‘measure of last resort’ to counter the danger of an imminent Iranian attack using nuclear weapons.
The shift in the temporal threshold of armed attack can be understood as a reinterpretation of the UN Charter:
The general prohibition of violence is superseded by the broadly defined right of self-defence, in which each state itself can determine the temporal threshold of the existence of an armed attack. The right of self-defence is reinterpreted from a legitimate right of reaction to a far-reaching right of defence against danger (Gefahrenabwehr).
Outlook
It must be recognised that Israel is extending the temporal boundaries of the threshold for the applicability of the right of self-defence. The fundamental principle of international law, the prohibition of the use of force in Art. 2 (4) UN-Charter, is showing signs of erosion. This is jeopardising the stability of the international legal order and the geopolitical landscape of the Middle East.
Assuming the attacks being tried to justify as acts of self-defence, Israel’s attacks on Iran exceed the limits of this instrument. There is no general right of self-defence in the sense of a comprehensive abstract defence against danger or self-defence against possibilities. The pre-emptive prevention of the use of force that has not yet materialised as an imminent threat is not covered by international law.
Even if it is unacceptable that Iran possesses such nuclear strike capability because of the threat it poses to Israel, there is no justification for the military action according to international law. In this respect, it is irritating when the EU and other states such as Germany recognise Israel’s right of self-defence in this case.
The fundamental principle of the prohibition of the use of force is not a negotiable instrument based on the subjective ideas of individual states; rather, it is a fundamental pillar of the international legal order and security. Any attempts to undermine it must be firmly rejected.
Citation: Studt, Tjorben, Dismantling the prohibition of the use of force by removing the boundaries of self-defence, JuWissBlog No. 57/2025, 25.06.2025, https://www.juwiss.de/57-2025/
This work is licensed under CC BY-SA 4.0.
