What’s Happening in International Law: Are Pre-Emptive Strikes by Israel Legal?

On 13^th June, 2025, Israel launched a major pre-emptive air campaign under the banner of “Operation Rising Lion” targeting the nuclear and military sites of Iran. The rationale behind the operations was to cripple the rising enrichment capabilities of Iran which Israel views as a threat.

What followed were a series of serious ballistic missile attacks from Iran as retaliation. Subsequently, the United States intervened by attacking three key nuclear sites in Iran using B2 Bombers. Iran retaliated once again, attacking a U.S military base in Qatar with missile strikes. 

Now, after nearly 12 days of conflict, the warring countries of Israel and Iran have announced and accepted ceasefire as proposed by US President Donald Trump. While this may be a moment of relief, the recent trend of pre-emptive strikes and the wars that follow them raise some pressing legal questions. The most prominent among them being- Whether such pre-emptive strikes are even legal under international law?

The commonly cited answer lies in a combined reading of Article 51 of the United Nation's (UN) Charter and the Caroline Test ("Caroline Doctrine") under customary international law.

Article 51 of the UN Charter states: “Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security.”

Simply understood, Article 51 recognises the inherent right to self-defence but only after an armed attack has occurred. A strict reading points to the fact that the Article does not allow anticipatory self-defence.

Despite this limitation, some states argue that Article 51 must be interpreted alongside customary international law. States like Israel and USA especially and more particularly argue in favor of the Caroline Doctrine. This doctrine justifies anticipatory self-defence when the threat is “instant, overwhelming, and leaving no choice of means, and no moment for deliberation.”

To fully understand this doctrine, one must look at its historical roots. During the 1837 Canadian Rebellions, British forces crossed into U.S. territory and destroyed the American steamboat “Caroline”, which was allegedly aiding Canadian rebels. In response, U.S. Secretary of State Daniel Webster wrote a letter to the British government which articulated the principle that anticipatory self-defence is lawful only when necessity is of an immediate and overwhelming nature (as stated above) leaving no time for deliberation. The Caroline Doctrine has since been invoked to justify pre-emptive strikes. To take an example, in 1981, Israel relied on it to justify its attack on Iraq’s Osirak nuclear reactor. Similarly in 2007, it invoked the doctrine after bombing a suspected nuclear facility in Syria.

However, this interpretation has not found acceptance in international courts. In the landmark case of Nicaragua v. United States (1986), the International Court of Justice (ICJ) held that while customary law and the UN Charter can be read together, any use of force must still fall within the strict limits of Article 51 which only permits self-defence in response to an actual armed attack. 

Two key criticisms arise from this legal status quo:

In today’s world of cyberwarfare, nuclear threats, and terrorism, the Caroline test feels outdated. Moreover, terms like instant and overwhelming are vague and open to broad, often biased interpretation.

On the other hand, the UN Charter’s strict requirement of an “armed attack” before action along with the ICJ’s refusal to recognise anticipatory self-defence are also problematic. They portray a priority given to reaction over prevention which often leaves states vulnerable to catastrophic threats like nuclear or large-scale terrorist attacks. In such scenarios if the law demands that states wait to be attacked first, then it renders the very concept of self-defence meaningless. As a result, states may often be left with two unsatisfactory options: either do nothing and risk grave harm or act unilaterally and face condemnation for breaching international law.

Both the Caroline Doctrine and the UN/ICJ’s strict interpretation of Article 51 suffer from equal flaws. While the former is vague and historically outdated, the latter is failing to reflect the complexities of modern strategic threats.

Thus, the need of the hour is a more balanced legal framework. This would entail retaining a high threshold for anticipatory self-defence along with recognition to limited scenarios where pre-emptive action may be necessary to prevent catastrophic harm. The legal vacuum surrounding pre-emptive strikes needs urgent attention. The international community must push for a well-recognised framework on pre-emptive strikes before it is too late.

Blog dated 24th June, 2025 is an original work of Gayatri Sawant (Student at Government Law College, Mumbai).