India’s BrahMos missile was used during Operation Sindoor, May 2025.
In the light of the Security Council's press statement, India's actions are justified under international law. Under Article 51, India has the right to self-defence when faced with an armed attack. Given the repeated cross-border terrorist incidents, India’s military response aligns with established legal principles of necessity and proportionality. Since Pakistan failed to prevent the actions of terrorist groups based in Pakistan and PoK, India could invoke state responsibility principles to justify counterterrorism operations. The unwilling or unable doctrine further supports India’s stance, allowing action when a host state fails to curb terrorist activities.
Can a state lawfully use force against non-state actors?
Traditionally, the law governing the use of force has focused on regulating armed conflicts between states. However, the rise in attacks by non-state actors in recent decades has called into question the adequacy of this framework in addressing modern security threats. This issue gained significant international attention following the 9/11 attacks on the World Trade Center, carried out by al-Qaeda1. In response, the UN Security Council adopted Resolution 1373 on 28 September 20012, which introduced broad measures to combat terrorism. Textual analysis of the resolution suggests that the Security Council unequivocally condemned terrorist attacks as a threat to international peace and security. The resolution reaffirmed the right to self-defence under the UN Charter and called on all states to cooperate in bringing the perpetrators to justice. It urged the international community to strengthen efforts to prevent and suppress terrorism through enhanced cooperation and implementation of relevant conventions. The Security Council also expressed its readiness to take necessary measures to combat terrorism.
Although Article 51 of the UN Charter does not indicate the nature of the attacker, the ICJ maintains the position expressed in the Nicaragua Case judgment, that only acts attributable to a state can constitute an ‘armed attack’. However, Judge Higgins in her dissenting opinion strongly opposed this view and contended that when force is employed by non-state actors, such as insurgent groups or terrorist organizations, the targeted state may invoke the right to self-defence in response to the attack.
This statement highlights a very contentious issue in modern international relations, namely the use of force in self-defence against non-state actors. Higgins relied on the definition outlined in Article 3(g) of the Definition of Aggression, annexed to General Assembly Resolution 3314 (XXIX)3. The provision states that, the sending by or on behalf of a State of armed bands, groups, irregulars or mercenaries, which carry out acts of armed force against another State of such gravity as to amount to the acts listed above, or its substantial involvement therein" constitutes an act of aggression.
This definition remains a significant provision in international law. It establishes that a State's direct or substantial involvement in supporting armed groups that engage in force against another State constitutes aggression. While the provision reinforces state responsibility for indirect uses of force, its practical application has been limited. The Security Council, which holds primary authority in determining acts of aggression, has rarely invoked this definition explicitly.
Additionally, the evolving nature of conflicts, especially those involving non-state actors, has led to differing interpretations of what constitutes "substantial involvement."
State responsibility and host nations' liability in cases of cross-border terrorism
State responsibility is a fundamental principle that holds a state legally accountable for internationally wrongful acts, including breaches of treaties, violations of customary international law, or non-compliance with international obligations. When a state engages in such conduct, it may be required to cease the wrongful act, provide reparations, or face consequences under international legal mechanisms. Its application is crucial in dealing with state involvement in armed conflicts, cross-border aggression, and support for non-state actors.
Article 1 of United Nations member states on the responsibility of states for internationally wrongful acts was adopted by the UN General Assembly in its 53rd session in 2001, establishes the principle that every internationally wrongful act by a state entails the responsibility of that state. Under International law, a state can be held responsible if it knowingly allows its territory to be used for acts that violate the rights of other states. This principle is reinforced by various treaties and conventions, including the International Convention for the Suppression of the Financing of Terrorism4 and UN Security Council Resolutions on Counterterrorism.
In Corfu Channel case (United Kingdom of Great Britain and Northern Ireland v. Albania)6, ICJ found that, ‘States have an obligation not to allow knowingly its territory to be used for acts contrary to the rights of other States’. The ruling affirmed that a state can be liable for wrongful acts within its territory, even in the absence of direct evidence. The Court permitted conclusions based on circumstantial proof, underscoring the obligation of states to exercise due diligence in preventing harm. This statement was reiterated in the case Congo v Uganda7.
Pakistan’s actions fall within the scope of Responsibility of States for Internationally Wrongful Acts 2001, which attributes responsibility to a state for the conduct of groups acting under its instruction, direction or control8. The persistent cross-border attacks targeting India over the past two decades reinforce the argument that Pakistan’s wrongful acts constitute an ongoing breach of its duty to cease and prevent the recurrence of such violations.
Changing global landscape in dealing with non-state actors
The terrorist attacks on September 11, 2001, fundamentally transformed the global security environment and U.S. counterterrorism policy. Prior to 9/11, international law was primarily oriented toward conflicts between sovereign states, where the use of force was heavily constrained by the UN Charter’s prohibition on aggression9. In the aftermath of 9/1110, the United States faced an unprecedented challenge: the decentralization of terrorist networks, which operate as non-state actors. This impetus forced policymakers to rethink long-held assumptions about the legal parameters that govern the use of force.
The attack on the Twin Towers in 2001, which initiated the US-led Global War on Terror.
In response, U.S. strategists began to rely on an emerging legal justification: the "unwilling or unable" doctrine11. The doctrine provides rationale for pre-emptive and retaliatory measures when a state does not effectively curb terrorist activities emanating from its territory12. This principle contends that if a state is either unwilling or incapable of preventing terrorist groups within its borders from launching attacks, then other nations have the right to exercise self-defence beyond conventional limits.
Essentially, it shifts the focus from state responsibility to a pragmatic assessment of threat, arguing that when a territorial power fails in its duty, the right to defend oneself transcends traditional barriers of sovereignty.
The application of the "unwilling or unable" doctrine has not been without controversy. Critics argue that it risks undermining the principles laid out in international law, especially the prohibition on the use of force enshrined in UN Charter Article 2(4). By granting an expansive interpretation of self-defence, there is concern that powerful states might bypass legal constraints and initiate military operations that could erode international stability. This debate intensifies when such doctrines are used to justify interventions in regions where attribution of responsibility to a state is ambiguous or where the legitimacy of evidence is in question.
Notably, the reliance on the "unwilling or unable" doctrine has had a profound impact on U.S. military operations in regions like Iraq and Syria13, where groups such as the Islamic State (ISIS) and affiliated networks have exploited power vacuums. These actions, while controversial, illustrate the ongoing struggle to craft a legal framework robust enough to address contemporary security challenges without compromising established international norms. The adoption of the "unwilling or unable"14 doctrine reflects a pragmatic response to a world where threats are no longer confined within clear state boundaries.
Conclusion
India has faced persistent security threats from Pakistan-based terrorist groups, particularly in Kashmir. Major incidents such as the 2008 Mumbai attacks, 2016 Pathankot airbase attack, 2019 Pulwama bombing and the April 2025 Pahalgam massacre have reinforced India’s argument that terrorism operating in Pakistan and PoK constitute an enduring threat to India.
The Security Council in its press statement dated 25 April 2025 condemned the Pahalgam terrorist attack. It reaffirmed that terrorism, in any form, poses a grave threat to international peace and security. The Council emphasised the need to hold perpetrators, organizers, financiers, and sponsors of this reprehensible act of terrorism accountable and bring them to justice. They emphasized the necessity of holding perpetrators accountable and called upon all States to fulfill their international legal obligations and adhere to relevant Security Council resolutions by actively cooperating with all relevant authorities in this regard.
Pakistan serves as a central hub for terrorist activities, hosting over 20 UN-designated extremist organizations while actively supporting cross-border terrorism. As detailed in “Country reports on terrorism 2023” published by the United States Government, India witnessed 94 terror-related events in Jammu and Kashmir, resulting in 117 fatalities, including 73 alleged terrorists, 30 security personnel, and 14 civilians.[1]
The official source of the United States Congress[2] states that U.S. officials have identified Pakistan as a base for numerous armed non-state militant groups, some of which have been active since the 1980s. These groups fall into five main categories: globally oriented, Afghanistan-focused, India- and Kashmir-centric, domestically driven, and sectarian (anti-Shia). Out of 15 listed groups, 12 are designated as Foreign Terrorist Organizations (FTOs) under U.S. law, with most adhering to Islamist extremist ideology.
In the light of the Security Council's press statement, India's actions are justified under international law. Under Article 51, India has the right to self-defence when faced with an armed attack. Given the repeated cross-border terrorist incidents, India’s military response aligns with established legal principles of necessity and proportionality. Since Pakistan failed to prevent the actions of terrorist groups based in Pakistan and PoK, India could invoke state responsibility principles to justify counterterrorism operations. The unwilling or unable doctrine further supports India’s stance, allowing action when a host state fails to curb terrorist activities.
US forces have invoked the “unwilling or unable”[3] rationale to justify repeated cross-border strikes against Taliban elements in Pakistan. Under President Bush, these actions comprised at least one covert ground raid in September 2008 alongside ongoing drone operations targeting militants on Pakistani soil[4]. Washington maintained that both the special-operations incursions and the UAV strikes fell within its right of self-defence, given Pakistan’s inability or reluctance to suppress the irregular fighters attacking U.S. troops in Afghanistan. This policy framework was carried forward into the Obama Administration.
India’s reliance on the unwilling or unable doctrine reflects the evolving nature of self-defence in international law. While the doctrine remains legally ambiguous, India’s actions align with its principles, particularly in response to cross-border terrorism. As security threats continue to challenge traditional legal frameworks, the doctrine’s legitimacy will depend on consistent state practice, judicial recognition, and multilateral consensus on its appropriate scope and limitations[5].
India’s response is consistent with international legal frameworks, including self-defence, state responsibility, and Security Council directives. By taking decisive action, India reinforces its commitment to counterterrorism, ensuring national security while adhering to international law.
The emergence of the “unable or unwilling” doctrine reflects a pragmatic adaptation of Article 51’s self-defence right to modern threats posed by non-State actors. Given the evolving security landscape, international courts play a pivotal role in shaping the doctrine’s contours. A purposive, teleological interpretation of Article 51, one that acknowledges non-State threats and the realities of cross-border terrorism, would harmonize the Charter’s prohibition on force with States’ duty to defend themselves.
By embracing a broader, context-sensitive reading, tribunals can ensure that self-defence law remains robust, coherent, and responsive to contemporary challenges.
(Exclusive to NatStrat)
Endnotes:
Revitalising the Tulbul Navigation Project for Jammu and Kashmir’s Development
