There has been much focus on Israeli violations of international humanitarian law (jus in bello) and possible genocide in Gaza. Less attention has been paid to Israel’s claim to self-defence (jus ad bellum) against the terrorist attack on 7 October 2023. However, the rules on self-defence address the legality of the overall purpose of the operations and the choice of military strategy. This is different from the lawfulness of the targeting in individual operations as governed by international humanitarian law or of a possible genocidal purpose of the operations.
Marko Milanovic [here] has doubted whether the UN Charter prohibition against the use of force and the right to self-defence is applicable, as well as the usefulness of the customary international law restrictions of necessity and proportionality. The content of these restrictions has also been debated by Adil Ahmad Haque [here and here] and Charles Kels [here] and by other authors. I will discuss, in the absence of universal recognition of Palestine as a state, the relevance of the rules on self-defence and point out their implications for restrictions on the Israeli military operations.
Prohibition against the use of force
The UN Charter Art. 2(4) prohibits the use of force in inter-state relations. There are convincing arguments that Palestine fulfils the legal requirement for statehood, especially after being accepted as observer state to the United Nations, and becoming party to several treaties, most notably the ICC Statute. However, there are different opinions on the extent to which Palestine should be considered a state under general international law, or only for specific purposes (‘functional statehood’), see here, here and here.
But even if Palestine should not possess statehood under general international law, the ICJ has confirmed that the Palestinian territory, based on customary international law, enjoy territorial integrity and thereby protection against the use of military force. This customary prohibition has in the Israel/Palestine conflict found expression in the Wall case (2004) where the ICJ stated that ‘the principles as to the use of force incorporated in the Charter reflect customary international law’ (para. 87). The Court also noted that ‘the principle of self-determination of peoples has been enshrined in the United Nations Charter and reaffirmed by the General Assembly in resolution 2625 (XXV) […], pursuant to which “Every State has the duty to refrain from any forcible action which deprives peoples referred to [in that resolution] … of their right to self-determination“‘ (para. 88, emphasis added).
This means that Israel does not have the right to use force on territory on which the Palestinian people is entitled to exercise its right of self-determination unless Israel can show a specific legal basis to do so. In that regard it is noteworthy that Security Council Resolution 2720 (2023) stressed that ‘[t]he Gaza Strip constitutes an integral part of the territory occupied in 1967’ and the Council was ‘reiterating the vision of the two-State solution, with the Gaza Strip as part of the Palestinian State’.
Given that Israel withdrew from Gaza in 2005, it cannot legally re-enter the territory with military forces unless such renewed territorial control can be based on the exercise of the right to self-defence. What is more, Israel claimed prior to the events on 7 October 2023 that Gaza did not constitute occupied territory. Accordingly, in Israel’s own view, its military operations could not be based on the rights of an occupying power under international humanitarian law [here and here].
Right to self-defence
Substance-wise, there can be no doubt that the attack on 7 October did constitute an ‘armed attack’ in terms of the threshold required by Art. 51. However, the ICJ, in its Wall opinion, denied Israel the right of self-defence against terrorist attacks for two reasons. First, it stated that Art. 51 governs the relationship between states, and that Israel had not claimed that the attacks came from a state. Second, it noted that Israel exercises control in the Occupied Palestinian Territory (OPT) and that the threats came from that territory (para. 139). Nevertheless, the Court acknowledged that Israel has the right, and even the duty, to protect its citizens, within the bounds of international law (para. 141).
The acceptance of Palestinian statehood has widely increased in the 20 years since the Wall opinion. What is more, a fundamental difference between the legal status of the West Bank and Gaza today is that Israel continues to exercise territorial jurisdiction over the former territory but since its withdrawal in 2005, not over Gaza. The underlying reason for the Court denying Israel the right of self-defence in the Wall must be explained by Israel’s jurisdictional control over the West Bank. This is different in Gaza where Israeli authorities have not been physically present after 2005. Therefore, the prohibition against self-defence on occupied territory should not apply in Gaza, regardless of whether Gaza generally is considered occupied.
The ICJ recognised in Wall that ‘the existence of a “Palestinian people” is no longer in issue’. It further noted that this has been accepted by Israel in an exchange of letters of 1993 with the PLO (para. 118). PLO has represented Palestine as observer in the UN General Assembly, see UNGA Resolution 67/19 (2012) [here]. Hamas won the Palestinian parliamentary elections in 2006 and has territorial control over Gaza. Nevertheless, it is the PLO that generally represents Palestine at the international level [here and here], including in territorial issues, peace and security.
Therefore, the Hamas attack on 7 October cannot be attributed to Palestine, whether it should be considered a state or a ‘self-determination unit’. This raises the question of the extent to which a state (Israel) has a right to self-defence against attacks from a non-state actor (Hamas). The rejection of self-defence against non-state actors in the Wall was criticized by a minority of the judges and the question was left open in Armed activities (2005) (para. 147). The scholarly debate has continued under the label of the ‘unable or unwilling’ doctrine, see e.g. here, here and here. I will not go into the debate about the extent to which a state has the right to self-defence against non-state actors, but in the following only assume that states have such a right.
Restrictions on the right to self-defence
In any case, the exercise of the right to self-defence must respect the customary international law requirements of necessity and proportionality. Proportionality is generally seen as comprising four elements, i.e. the legitimacy of the reason for rights limitation; the suitability of a measure for obtaining the purpose; the necessity in the sense that the least restrictive measure should be chosen; and, finally, the balancing of the benefit of the measure relative to the importance of protecting the obligation (the stricto sensu analysis) [here and here]. The principle of proportionality is generally accepted as the appropriate approach in the balancing of protected rights and, on the other hand, other legitimate interests [here].
The Israeli military operations should be questioned in relation to these proportionality elements. First, Israel was clearly allowed to halt and repel the Hamas attack. Moreover, the liberation of the hostages is a legitimate purpose. Self-defence arguably also allows the prevention of reasonably foreseeable future threats. However, many have challenged the reasons for and overall effect of the massive operations. They may be seen as expressions of illegal punishment or revenge. The ICJ has, in its provisional measures in the case raised by South Africa [here], not even excluded a genocidal purpose.
We do not have clear guidance from the ICJ and state practice about how to operationalize the stricto sensu balancing in different contexts. But there is general agreement among scholars that proportionality in jus ad bellum, as expressed by Kretzmer, ‘includes (but is certainly not confined to) damage to combatants and military objects’. Recent scholarship by Tams and Brückner, Henderson and O’Meara also shows that states and scholars have condemned the Israeli military intervention in Lebanon in 2006 and earlier military actions in Gaza (2009, 2012 and 2014) as disproportionate. In the Gaza context, it is, on the one hand, not obvious that the massive Israeli attack, with the extensive loss of life and destruction, is well suited to secure the release of the remaining hostages. It is also difficult to imagine that Israel would once again face a surprise attack comparable to what happened on 7 October. On the other hand, the losses and damages in Gaza are strikingly more dramatic than the ones experienced in Lebanon in 2006. If the destructions in Lebanon could be considered disproportionate, Gaza is clearly beyond the limits of lawful ad bellum use of force.
Marko Milanovic [here] has doubted whether the UN Charter prohibition against the use of force and the right to self-defence is applicable, as well as the usefulness of the customary international law restrictions of necessity and proportionality. The content of these restrictions has also been debated by Adil Ahmad Haque [here and here] and Charles Kels [here] and by other authors. I will discuss, in the absence of universal recognition of Palestine as a state, the relevance of the rules on self-defence and point out their implications for restrictions on the Israeli military operations.
Prohibition against the use of force
The UN Charter Art. 2(4) prohibits the use of force in inter-state relations. There are convincing arguments that Palestine fulfils the legal requirement for statehood, especially after being accepted as observer state to the United Nations, and becoming party to several treaties, most notably the ICC Statute. However, there are different opinions on the extent to which Palestine should be considered a state under general international law, or only for specific purposes (‘functional statehood’), see here, here and here.
But even if Palestine should not possess statehood under general international law, the ICJ has confirmed that the Palestinian territory, based on customary international law, enjoy territorial integrity and thereby protection against the use of military force. This customary prohibition has in the Israel/Palestine conflict found expression in the Wall case (2004) where the ICJ stated that ‘the principles as to the use of force incorporated in the Charter reflect customary international law’ (para. 87). The Court also noted that ‘the principle of self-determination of peoples has been enshrined in the United Nations Charter and reaffirmed by the General Assembly in resolution 2625 (XXV) […], pursuant to which “Every State has the duty to refrain from any forcible action which deprives peoples referred to [in that resolution] … of their right to self-determination“‘ (para. 88, emphasis added).
This means that Israel does not have the right to use force on territory on which the Palestinian people is entitled to exercise its right of self-determination unless Israel can show a specific legal basis to do so. In that regard it is noteworthy that Security Council Resolution 2720 (2023) stressed that ‘[t]he Gaza Strip constitutes an integral part of the territory occupied in 1967’ and the Council was ‘reiterating the vision of the two-State solution, with the Gaza Strip as part of the Palestinian State’.
Given that Israel withdrew from Gaza in 2005, it cannot legally re-enter the territory with military forces unless such renewed territorial control can be based on the exercise of the right to self-defence. What is more, Israel claimed prior to the events on 7 October 2023 that Gaza did not constitute occupied territory. Accordingly, in Israel’s own view, its military operations could not be based on the rights of an occupying power under international humanitarian law [here and here].
Right to self-defence
Substance-wise, there can be no doubt that the attack on 7 October did constitute an ‘armed attack’ in terms of the threshold required by Art. 51. However, the ICJ, in its Wall opinion, denied Israel the right of self-defence against terrorist attacks for two reasons. First, it stated that Art. 51 governs the relationship between states, and that Israel had not claimed that the attacks came from a state. Second, it noted that Israel exercises control in the Occupied Palestinian Territory (OPT) and that the threats came from that territory (para. 139). Nevertheless, the Court acknowledged that Israel has the right, and even the duty, to protect its citizens, within the bounds of international law (para. 141).
The acceptance of Palestinian statehood has widely increased in the 20 years since the Wall opinion. What is more, a fundamental difference between the legal status of the West Bank and Gaza today is that Israel continues to exercise territorial jurisdiction over the former territory but since its withdrawal in 2005, not over Gaza. The underlying reason for the Court denying Israel the right of self-defence in the Wall must be explained by Israel’s jurisdictional control over the West Bank. This is different in Gaza where Israeli authorities have not been physically present after 2005. Therefore, the prohibition against self-defence on occupied territory should not apply in Gaza, regardless of whether Gaza generally is considered occupied.
The ICJ recognised in Wall that ‘the existence of a “Palestinian people” is no longer in issue’. It further noted that this has been accepted by Israel in an exchange of letters of 1993 with the PLO (para. 118). PLO has represented Palestine as observer in the UN General Assembly, see UNGA Resolution 67/19 (2012) [here]. Hamas won the Palestinian parliamentary elections in 2006 and has territorial control over Gaza. Nevertheless, it is the PLO that generally represents Palestine at the international level [here and here], including in territorial issues, peace and security.
Therefore, the Hamas attack on 7 October cannot be attributed to Palestine, whether it should be considered a state or a ‘self-determination unit’. This raises the question of the extent to which a state (Israel) has a right to self-defence against attacks from a non-state actor (Hamas). The rejection of self-defence against non-state actors in the Wall was criticized by a minority of the judges and the question was left open in Armed activities (2005) (para. 147). The scholarly debate has continued under the label of the ‘unable or unwilling’ doctrine, see e.g. here, here and here. I will not go into the debate about the extent to which a state has the right to self-defence against non-state actors, but in the following only assume that states have such a right.
Restrictions on the right to self-defence
In any case, the exercise of the right to self-defence must respect the customary international law requirements of necessity and proportionality. Proportionality is generally seen as comprising four elements, i.e. the legitimacy of the reason for rights limitation; the suitability of a measure for obtaining the purpose; the necessity in the sense that the least restrictive measure should be chosen; and, finally, the balancing of the benefit of the measure relative to the importance of protecting the obligation (the stricto sensu analysis) [here and here]. The principle of proportionality is generally accepted as the appropriate approach in the balancing of protected rights and, on the other hand, other legitimate interests [here].
The Israeli military operations should be questioned in relation to these proportionality elements. First, Israel was clearly allowed to halt and repel the Hamas attack. Moreover, the liberation of the hostages is a legitimate purpose. Self-defence arguably also allows the prevention of reasonably foreseeable future threats. However, many have challenged the reasons for and overall effect of the massive operations. They may be seen as expressions of illegal punishment or revenge. The ICJ has, in its provisional measures in the case raised by South Africa [here], not even excluded a genocidal purpose.
We do not have clear guidance from the ICJ and state practice about how to operationalize the stricto sensu balancing in different contexts. But there is general agreement among scholars that proportionality in jus ad bellum, as expressed by Kretzmer, ‘includes (but is certainly not confined to) damage to combatants and military objects’. Recent scholarship by Tams and Brückner, Henderson and O’Meara also shows that states and scholars have condemned the Israeli military intervention in Lebanon in 2006 and earlier military actions in Gaza (2009, 2012 and 2014) as disproportionate. In the Gaza context, it is, on the one hand, not obvious that the massive Israeli attack, with the extensive loss of life and destruction, is well suited to secure the release of the remaining hostages. It is also difficult to imagine that Israel would once again face a surprise attack comparable to what happened on 7 October. On the other hand, the losses and damages in Gaza are strikingly more dramatic than the ones experienced in Lebanon in 2006. If the destructions in Lebanon could be considered disproportionate, Gaza is clearly beyond the limits of lawful ad bellum use of force.