On October 7, 2023, over 1,000 Hamas militants launched a deadly attack into southern Israel, killing around 1,200 civilians—including men, women, and children—and abducting 250 people who were taken into Gaza. This incident became the deadliest attack on Jews since the Holocaust. In response, Israeli Prime Minister Benjamin Netanyahu declared, “Israel is at war,” and the Israel Defense Forces (IDF) began a military campaign aimed at defeating Hamas and rescuing the hostages. Since then, the conflict has resulted in the deaths of more than 54,000 Palestinians, many of them women and children.

Israel has insisted that its military actions are justified under international law, particularly under the principle that every state has an inherent right to defend itself. Netanyahu reiterated this in early 2024, citing Article 51 of the United Nations Charter, which affirms that nations can defend themselves if attacked. Initially, the international community largely supported Israel’s right to defend itself, as long as its military actions complied with international humanitarian law. However, nearly two years after the initial Hamas attack, there is growing debate over whether Israel’s continued military operations can still be defended under the legal framework of self-defense.

The principle of self-defense in international law has a long history. It was notably discussed in the 1837 Caroline incident, in which the use of force in self-defense was required to be necessary and not excessive. The principle evolved further during World War II and has expanded in modern times to include threats from non-state actors such as al-Qaeda. As a sovereign state and member of the United Nations, Israel has the right to respond to threats from both countries and armed groups like Hamas. However, this right is not without limits. It must meet the legal standards of necessity and proportionality. The necessity of Israel’s initial response was widely acknowledged, given the brutality of the October 7 attacks and the hostage situation. At first, the proportionality standard was also seen as met, with military efforts focused on rescuing hostages and neutralizing Hamas’s immediate threat.

But questions have now arisen about whether Israel’s ongoing actions remain proportionate. Statements from Israeli officials, such as Defense Minister Israel Katz’s May 2024 comment that Hamas would be “annihilated” unless a ceasefire was accepted, suggest that the scale of Israel’s response may no longer align with the principles of self-defense. Proportionality must be maintained throughout a conflict, not just at its onset. International law allows military action until the aggressor is defeated, but it does not permit the total destruction of the territory from which the attack originated. Moreover, the law requires military actions to avoid excessive harm to civilians and to be aimed at enemy forces.

Although Israel has targeted Hamas operatives, the broader campaign has led to massive civilian casualties, widespread damage, and reports of famine-like conditions in Gaza. These consequences have led many to argue that Israel’s use of force has exceeded what is legally permissible under self-defense. While some might claim Israel is still acting to free hostages, such an argument is contentious. Though Israel previously carried out a high-profile hostage rescue in Entebbe in 1976, modern international law offers few precedents for treating hostage rescues as grounds for prolonged military campaigns, especially of this magnitude.

If self-defense can no longer justify Israel’s actions, then the legal framing may shift toward identifying them as acts of aggression. Israel might contend that it is operating as an occupying power responsible for maintaining security. However, the International Court of Justice has previously deemed Israel’s occupation of Gaza illegal, though it didn’t address developments after October 7. Despite not reoccupying Gaza entirely, Israel’s effective control over the territory suggests it is still functioning as an occupying force. Yet, the intensity and duration of its operations surpass what would be considered reasonable for such a role.

In the absence of a valid legal justification, Israel’s military campaign may be interpreted as an act of aggression under international law. The UN Charter and the Rome Statute of the International Criminal Court define aggression to include invasions, bombings, and blockades—all of which have occurred in Gaza. The global community has consistently condemned Russia’s invasion of Ukraine as an act of aggression. The pressing question now is whether it will apply the same legal and moral standards to Israel’s actions in Gaza.