India’s ‘Operation Sindoor’ targeting “terrorist infrastructure” in Pakistan and Pakistan-occupied Kashmir following the Pahalgam terrorist attack presents a complex scenario for analysis under international law. The legality of such an operation involves consideration of both the law governing the resort to force between States (jus ad bellum) and the law governing the conduct of hostilities within an armed conflict (jus in bello), also known as International Humanitarian Law (IHL). These two branches of law are distinct, although they may operate in parallel or even interact in certain contexts.

I. Operation Sindoor

According to available statements, India conducted targeted strikes against nine specific sites described as “terrorist infrastructure” on 7 May 2025, in response to a terror attack that killed 26 civilians two weeks prior. India characterised its actions as “focused, measured and non-escalatory,” emphasising that no Pakistani military facilities were targeted, demonstrating “considerable restraint in selection of targets and method of execution”.

Pakistan, however, described the Indian action as a “flagrant violation of the UN Charter, international law, and established norms,” claiming that India targeted six sites, resulting in 24 impacts, killing eight Pakistanis, including a child, and injuring 35 others. Pakistan also stated the attack posed a “grave threat to commercial air traffic”. Pakistan reserved the right to respond under Article 51 of the UN Charter.

II. Jus ad Bellum: The Right to Use Force

The jus ad bellum governs when a State may lawfully use force. The general prohibition on the unilateral use of force is enshrined in Article 2(4) of the UN Charter. Exceptions include self-defence, codified in Article 51 of the UN Charter.

India’s operation was explicitly framed as a response to a terrorist attack. This immediately raises complex jus ad bellum questions regarding self-defence against non-State actors operating from the territory of another State, an issue the International Court of Justice has approached cautiously. Pakistan’s statement reserving its right to respond under Article 51 of the UN Charter indicates it views the situation through the lens of self-defence.

Assuming jus ad bellum permits a State to use force in self-defence against a non-State actor like a terrorist group operating from another State’s territory (a debated point in international law), the response must satisfy the conditions of necessity and proportionality. Jus ad bellum proportionality is not assessed against the original attack suffered, but in relation to what is necessary to halt or repel the armed attack and to recover territory. It can involve considering the scale of the overall operation, its scope relative to the target State’s territory, and the types of weapons used. There are different views on whether jus ad bellum proportionality is assessed quantitatively or qualitatively, focusing on the objective of stopping hostile activities. Some argue that civilian casualties may play a role in this assessment, while others claim they do not. The strategic-level jus ad bellum analysis might even consider avoiding future civilian suffering as a military advantage.

India’s description of the operation as “focused, measured and non-escalatory” and demonstrating “considerable restraint” speaks to the necessity and proportionality considerations under jus ad bellum. Whether the scale, duration, and target selection of Operation Sindoor were necessary and proportionate to the objective of halting the threat from cross-border terror planning is a matter of jus ad bellum assessment, distinct from the IHL assessment of individual strikes.

III. Jus in Bello (IHL): Conduct of Hostilities

Even if the resort to force is deemed legal under jus ad bellum, all military operations must comply with IHL. A key principle of IHL is the principle of proportionality in attack. This principle, reflected in Article 51(5)(b) of Additional Protocol I and accepted as customary international law, prohibits attacks which may be expected to cause incidental loss of civilian life, injury to civilians, or damage to civilian objects which would be excessive in relation to the concrete and direct military advantage anticipated. This prohibition applies even when attacking a legitimate military objective.

Assessing compliance with IHL proportionality requires examining several components:

1. Legitimate Military Objective: The attack must be directed at a specific military objective. India stated it targeted “terrorist infrastructure”. Legitimate military objectives are generally defined as objects which, by their nature, location, purpose, or use, make an effective contribution to military action and whose total or partial destruction, capture, or neutralisation, in the circumstances ruling at the time, offers a definite military advantage.
2. Anticipated Civilian Harm: The commander must assess the expected incidental civilian casualties and damage to civilian objects. This assessment is crucial and must be made from the perspective of the attacker at the time the attack was ordered or decided upon, not with hindsight based on the actual outcome. The danger depends on various factors like location, weapon accuracy, weather, and the nature of the objective. India described its operation as “precise and restrained”, suggesting an attempt to minimise civilian harm, which is relevant to this assessment and the obligation to take precautions.
3. Anticipated Military Advantage: The commander must assess the concrete and direct military advantage expected from the attack. This advantage can be considered at various levels (tactical, operational, strategic), although the term “concrete and direct” primarily points to tactical advantage. However, State declarations and practice, as well as analyses of cases like the North Korean artillery attacks, suggest that considering operational or strategic advantages is common. Disrupting “cross-border terror planning” could be considered an operational or strategic military advantage.
4. Excessiveness: The core of the IHL proportionality test is balancing the anticipated civilian harm against the anticipated military advantage. The attack is prohibited if the expected civilian harm is excessive in relation to the expected military advantage. This balancing is inherently difficult and depends on the specific circumstances of each case. The standard is excessiveness, which is stricter than the “clearly excessive” standard used for war crimes prosecution under the Rome Statute. While the sheer magnitude of civilian damage (“extensiveness”) does not automatically make an attack disproportionate if the military advantage is sufficiently large, it is suggested that extensive civilian damage would normally be excessive.

IV. Application to Operation Sindoor

Determining whether Operation Sindoor complied with IHL proportionality is challenging based solely on the public information provided in the sources.

• Target: India claims to have targeted “terrorist infrastructure”. Whether these specific sites qualify as legitimate military objectives under IHL requires further information about their “nature, location, purpose, or use”.
• Proportionality Assessment: The key is India’s ex ante assessment. What level of civilian harm did Indian commanders expect from striking the nine sites, and what concrete and direct military advantage did they anticipate? India’s statement about precision and restraint suggests an effort to minimise expected civilian harm. The military advantage is likely related to disrupting future attacks, which could be considered at an operational or strategic level. Pakistan’s claims of civilian deaths are ex post outcomes. While tragic, the fact that civilian deaths occurred does not automatically prove that India’s ex ante proportionality assessment was unlawful. An IHL violation occurs only if the expected civilian damage was excessive when the attack was planned. Assessing this requires knowing the information India had at the time.
• Precautions: IHL requires taking feasible precautions to minimise civilian harm. India’s emphasis on “precise and restrained” execution and target selection is relevant to the precautions taken. Whether all “feasible precautions” were taken is a factual inquiry.
• Individual Responsibility: The proportionality rule applies at all levels, including potentially individual soldiers. While the operational decision may be made by commanders, those executing the attack also bear responsibility.

V. Conclusion

Assessing the legality of Operation Sindoor under international law requires applying both jus ad bellum and jus in bello.

Under jus ad bellum, the legality depends on whether the operation constitutes a lawful act of self-defence against a non-State actor and whether the overall response was necessary and proportionate to halt the threat. India’s framing of the operation as a “measured and non-escalatory response” is relevant here.

Under jus in bello, the legality of each strike depends on whether the targets were legitimate military objectives and whether the anticipated civilian harm was excessive in relation to the anticipated concrete and direct military advantage, assessed at the time of the attack from the attacker’s perspective. India’s claims of precision and restraint are relevant to its compliance with IHL. Pakistan’s claims of civilian casualties, while serious and potentially triggering duties to investigate, are ex post results and do not, in themselves, prove an ex ante violation of the IHL proportionality rule.

A definitive legal assessment cannot be made without more detailed information regarding India’s planning process, intelligence available at the time of the attack, specific targeting decisions, and the ex ante proportionality assessments conducted for each strike.

In conclusion, Operation Sindoor illustrates the ongoing challenges of applying international law, particularly the proportionality principle, in the context of responses to terrorism involving non-State actors and cross-border operations.

Mohit Kumar Manderna & Kritika Vatsa are BBA LL.B. (Hons.) students at Jindal Global Law School, O.P. Jindal Global University. Interests include International Relations, Sociology, Economics and History.