Introduction:

To counter the growing menace of cross-border terrorism and the recent Pahalgam attack, India launched Operation Sindoor as a military response against terrorist havens purportedly based in Pakistan-occupied territories. Although the operation has received broad domestic public acclaim, it also provokes important questions in international law, most notably the principles of necessity, proportionality, and civilian protection under the Law of Armed Conflict (LOAC) or International Humanitarian Law (IHL). This article examines the legal aspects of the operation using a thoughtful approach.

Operation Sindoor is a turning point where the strictures of orthodox international legal principles come up against the changing imperatives of national security against contemporary asymmetric threats. It calls into question, on the one side, the traditional norms of state sovereignty and the ban on the unilateral employment of force—doctrines long preserved by legal conservatism under the UN Charter.

This operation, therefore, is not just a military manoeuvre but a legal and diplomatic assertion that the international legal order must adapt to contemporary security realities.

Why Name Operation Sindoor?

Sindoor, or vermilion powder, is an old symbol of the marital status of Hindu women. Married women place it either in their hair parting or on their foreheads, and they smear it off if they are widowed. In the terrorist attack on April 22, there were many women who lost their husbands, who were targeted because they were Hindus. But hardly any got the kind of media attention that Ms. Narwal has after a photo of her standing by her husband’s side became viral.

The Indian government’s decision to name the operation Operation Sindoor indicated that it wanted revenge for the widowed women.[1]

The Catalyst Behind This Operation:

In retaliation for the Pahalgam massacre that had taken away the lives of 26 civilians, India had carried out precision military attacks on terrorist infrastructure in Pakistan and Pakistan-occupied Kashmir (PoK) under “Operation Sindhoor”.[2]

Though India termed its moves as “measured and non-escalatory,” Pakistan called them a “blatant act of war.”

The episode prompts questions regarding the legality of India’s response under international law and new global doctrines for state actions towards cross-border terrorism.

The Legal Threshold: ‘Armed Attack’ By Non-State Actors

Under Article 51 of the UN Charter, states enjoy an “inherent right of individual or collective self-defence if an armed attack occurs.” For decades, there was controversy over whether attacks by non-state actors, such as terrorist organisations, could activate this right. But post-9/11 state practice has moved radically on from that.[3]

Tom Ruys, in “Armed Attack” and Article 51 of the UN Charter: Evolutions in Customary Law and Practice, observes a discernible trend towards states claiming self-defence against major terror attacks even when not directly imputable to a state. Ruys identifies that customary international law has evolved to accept that non-state actors can commit “armed attacks” if the scale and effects are comparable to traditional military attacks. The 9/11 attacks and subsequent U.S. intervention in Afghanistan, supported by Security Council Resolutions 1368 and 1373, solidified this view. Ruys’ references state reactions following 9/11 as proof that “armed attacks” do not necessarily have to come from a state to activate the right of self-defence.

India, therefore, has a clear legal ground on which it can contend that when outfits like Lashkar-e-Taiba or Jaish-e-Mohammed carry out mass, coordinated attacks like the 2001 Parliament attack or the 2008 Mumbai massacre, these constitute armed attacks under Article 51.

Attribution And State Responsibility:

Whereas attacks by non-state actors will mobilize self-defence, attribution, i.e., connecting the host state to the activities of the group, is essential. India’s case stands strengthened here as well.

International Court of Justice (ICJ) in the Nicaragua case (Case Concerning Military and Paramilitary Activities in and Against Nicaragua, 1986) held that conferring “substantial involvement” funding, training, or equipping armed groups is tantamount to indirect use of force.[4] Although the ICJ drew back from equating this with “armed attack,” subsequent practice has undermined this constraint. Ruys points out an increasing recognition that when a state is “unwilling or unable” to stop attacks emanating from its territory, and is doing so by tacit or active cooperation, self-defence is legitimate. This is the criterion used by the US in Afghanistan, Turkey in Syria, and Israel in Lebanon. If India can demonstrate active Pakistani complicity or habitual failure to prevent groups from operating with impunity, it might be able to justify proportionate defensive action.

This is not an abstract argument. The 26/11 Mumbai attacks were led back to handlers based in Pakistan. Hafiz Saeed, the supposed mastermind, functioned openly for decades. Indian dossiers submitted at the United Nations and FATF show ongoing safe havens for terror infrastructure on the other side of the border. In the event of another 26/11-style attack, India would have a robust case to assert a violation of Article 2(4) by Pakistan and invoke self-defence under Article 51.

Necessity, Proportionality, And Reporting Obligations:

Even if a state legitimately resorts to self-defence, it is subject to two conventional preconditions: necessity and proportionality. Necessity entails that there are no reasonable alternatives, diplomatic or otherwise, to halt the threat. In light of Pakistan’s continued failure to act on actionable intelligence and refusal to acknowledge complicity, this threshold may well be deemed satisfied by another egregious attack. Proportionality entails that India’s response is proportionate in scale to the armed attack. This does not mean symmetry, i.e., a terrorist ambush does not require a response in the form of an ambush, but the response has to be focused and restricted to disabling the threat.

Second, India would be obligated under Article 51 to notify the UN Security Council. Although the ICJ in Nicaragua found that non-reporting did not render self-defence unlawful, reporting adds legitimacy and conforms to global expectations.

Precedents And Indian Record Of Restraint

Indian historical behavior is an exemplary restraint. Following the 2001 Parliament attack and the 2008 Mumbai attacks, India did not immediately retaliate with kinetic action. Even the 2016 Uri attack was met only with a limited “surgical strike” across the Line of Control, not all-out war. Likewise, the 2019 Balakot airstrike after Pulwama was measured to ensure that it did not escalate.[5]

India has not misused or exploited the doctrine of self-defence. Its ultimatums now are a result of a series of provocations in international law that arguably reach the “armed attack” threshold. The 2006 Israeli attack on Hezbollah in Lebanon, Turkish action against Kurdish fighters in Syria, and even French air strikes in Mali following terror attacks—all set precedents in which countries acted in self-defence against non-state actors beyond territorial boundaries.

Case Law:

The International Court of Justice in “Nicaragua v. United States”[6] (1986) emphasized that only attacks of sufficient scale and gravity qualify as “armed attacks”.

Conclusion: A Lawful And Measured Posture

India’s statement that any subsequent act of terrorism from Pakistan will be considered an act of war is not just a piece of rhetorical flair but a careful and calculated legal position. The new policy conforms to the changing interpretations of international law, especially after 9/11. Legal thinkers like Tom Ruys have pointed out that practice by states and opinio juris after 2001 have broadened the acceptable scope of self-defense from classical state-to-state violence to retaliation against non-state actors in instances where there is proof of state complicity or negligence. India’s stance marks this evolution in law, marking a break with strategic restraint doctrines in the past. By making the claim that future terrorist attacks won’t be taken diplomatically, India is stressing its willingness to invoke its right to defend itself under Article 51 of the United Nations Charter, which allows for states to defend themselves against armed attacks, including those staged by non-state actors with state sponsorship.

This change in policy is highlighted by recent developments, like the Pahalgam terror attack, which caused major casualties and was blamed on Pakistan-based terrorist outfits.

India, in turn, launched Operation Sindoor, hitting terror infrastructure in Pakistan and Pakistan-occupied Kashmir. These moves demonstrate India’s seriousness in adopting its new policy of declaring acts of terrorism acts of war and taking all steps necessary. The international community hasn’t missed this change, and India’s actions have been framed as self-defense and acts against terror. In addition, India’s stand has been maintained through international diplomacy, such as UN declarations, where it has called for the implementation of a universal zero-tolerance policy against terrorism and highlighted the role Pakistan supposedly plays in supporting terrorist organizations. Pakistan is increasingly falling under attack from criticism at the international level for being suspect of supporting terrorist groups operating in the country. India’s warning is, therefore, a call to Pakistan to take immediate steps against dismantling terrorist networks and to prevent future attacks.

Failing to do so has legal implications in the sense of potential military intervention justified on the basis of international law. India’s policy is to enforce the universal rule of law by holding states accountable for hosting or facilitating terrorist activities. This policy not only discourages but also tries to uphold the high standards of international law by immunizing states from avoidance of responsibility for acts of terrorism contracted out of their territories. In this regard, India’s policy is not a contravention of international norms but an upholding of the legal responsibilities that all states have in fighting terrorism.

[1] Mujib Mashal, Hari Kumar, Salman Masood, ‘India Strikes Pakistan but Is Said to Have Lost Aircraft’ (2025) The New York Times https://www.nytimes.com/2025/05/06/world/asia/india-strikes-pakistan.html.

[2] Ekata Deb, ‘Operation Sindoor: India’s Cross-Border Strike in the Eyes of International Criminal Law – [Part-01]’ (2025) LinkedIn https://www.linkedin.com/pulse/operation-sindoor-indias-cross-border-strike-eyes-criminal-ekata-deb-2kx0c.

[3] Apurva Neel, ‘Operation Sindoor and the Law of Armed Conflict: Proportionality, Necessity, and Civilian Safety’ (2025) Legal Bites https://www.legalbites.in/international-law/operation-sindoor-and-the-law-of-armed-conflict-proportionality-necessity-and-civilian-safety-1140630.

[4] Shashank Maheshwari, ‘Operation Sindoor and the legal case for India’s right to self-defence’ (2025) The Times of India https://timesofindia.indiatimes.com/blogs/voices/operation-sindoor-and-the-legal-case-for-indias-right-to-self-defence/.

[5] Juris Hour, ‘Operation Sindoor: India’s Precision Strikes Against Terror Camps in Pakistan and PoK’ (2025) https://www.jurishour.in/columns/operation-sindoor-india-terror-pakistan-pok/.Jurishour+4

[6] Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. United States of America), 1986 I.C.J. 14.

By: Devangi Jaiswal