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Unpacking Jus Ad Bellum Proportionality And Examining Its Relationship With The Jus In Bello In Light Of The Equal Application Principle, Jared Dass

International Law Studies

The jus ad bellum is one of the most important areas of international law, with the prohibition on the use of force forming the cornerstone of the UN Charter. However, a lack of doctrinal clarity, especially regarding the jus ad bellum proportionality principle, undermines its ability to meaningfully regulate the use of force by States in self-defense. There is further lack of understanding as to how the jus ad bellum interacts with the jus in bello, in particular as between the two proportionality principles found in both bodies of law. The orthodox view rejects any such interaction, for fear …

Military Ai And The Specter Of The Limitless War, Yuval Shany, Yahli Shereshevsky

International Law Studies

Legal and extra-legal factors related to the development of international humanitarian law (IHL) support the exercise of strategic restraint during armed conflicts. We claim, however, that technological developments in the area of military artificial intelligence (AI) fundamentally do away with many of the technological constraints that limited the capacity of militaries to fully utilize the “license to kill” afforded to them by IHL. Such a violence-enhancing effect can become even more dramatic in cases where other restraining factors are less effective. The upshot of our analysis is that the implicit assumption that IHL would be applied in a context of …

Symposium—Introduction, Russell Buchan

International Law Studies

In March 2025 the University of Reading and the U.S. Naval War College convened a workshop at the University of Reading in the United Kingdom to examine the application of the jus ad bellum, jus in bello, and international criminal law to the use of military AI. This is the introduction to the symposium, published as Volume 107 of International Law Studies.

Assessing The Role Of Ai In Determining The Necessity And Proportionality Of The Exercise Of Self-Defense Against An Armed Attack, Marco Roscini

International Law Studies

This article explores whether artificial intelligence (AI) constitutes an asset or rather a challenge in assessing the necessity and proportionality of a State’s response to an armed attack in the context of self-defense. Two central arguments are advanced. First, while AI may assist in detecting incoming threats of armed attacks, abstract and highly context-driven notions like necessity and proportionality would be very difficult to encode into algorithms. Second, even assuming that this were possible, relying on AI to determine the necessity and proportionality of a self-defense response would present as many challenges as it does advantages and, therefore, should be …

Artificial Intelligence And The Prohibition On The Use Of Force: Intention And Causation, Russell Buchan

International Law Studies

This article explores the application of Article 2(4) of the United Nations Charter to AI-enabled systems that carry out unintended engagements involving the use of force. First, it analyzes whether State responsibility for a breach of the prohibition on the use of force is defined in subjective or objective terms. Most commentators maintain that a State must intend to use force against the victim State in order for the prohibition to apply. However, through an examination of State practice, this article demonstrates that the prohibition is based on objective responsibility. Second, this article assesses whether a State must cause the …

Artificial Intelligence And The “Armed Attack” Threshold In International Law, Katie A. Johnston

International Law Studies

This article argues that the deployment of artificial intelligence, even in its strong fully autonomous form, does not have significant consequences for the application of the jus ad bellum framework, and in particular the armed attack threshold. As with all new weapons technologies, the deployment of artificial intelligence in the resort to force requires consideration of what “imminence” means in this context. However, artificial intelligence is fundamentally a means of making decisions to resort to force or contributing to the reasons for which such decisions are made by humans. Unlike the jus in bello, the jus ad bellum is …

Classification Of The Armed Conflicts In The Near East, Marco Sassòli

International Law Studies

This article explores the proper classification of Israel’s current conflicts with Hamas and Hezbollah as international or non-international armed conflicts. It discusses the different possibilities of how the international humanitarian law of international or non-international armed conflict applies to those conflicts and whether and to what extent the international humanitarian law of military occupation applies to the conduct of Israel Defence Forces in the Gaza Strip and Lebanon. It also explains why the proper classification of the conflicts still matters and is not only an intellectual exercise for scholars or students. While every conflict has its specifics, the article deals …

Iran And Its Proxies: Attribution And State Responsibility, Jennifer Maddocks

International Law Studies

Iran has invested heavily in proxy militias since the regime's founding in 1979. In the decades that followed, groups such as Hezbollah in Lebanon, Shi'a militias in Iraq and Syria, and the Houthis in Yemen have projected Iran's influence across the region. Today, Iran's proxy network is considerably weakened due to Israel's military actions following October 7, 2023, and the fall of the Assad regime in Syria. Yet the Houthis' attacks on Israel and against Red Sea shipping demonstrate how Iran's support to these groups continues to facilitate their conduct in violation of international law. This article examines Iran's potential …

Commander, U.S. Indo-Pacific Command, Remarks At The 2025 Military Law And Operations Conference, Samuel J. Paparo

International Law Studies

Admiral Samuel J. Paparo, Commander, U.S. Indo-Pacific Command, Remarks at the Military Law and Operations Conference, September 8, 2025

Cosmic Force: A Framework For Applying The Prohibition Of The Use Of Force In Outer Space, Erin Pobjie

International Law Studies

Outer space is becoming increasingly contested and existing approaches to identifying prohibited force in outer space lack a systematic foundation, hindering their application to novel challenges such as temporary interference with critical satellites or threats involving commercial space actors. This article addresses this gap by developing the first comprehensive, multifactorial legal framework for identifying a prohibited use of force in outer space. This framework provides a structured method for analyzing non-kinetic actions, temporary effects, and persistent hazards like space debris. It fundamentally advances existing legal approaches in three ways. First, it establishes when States can be implicated in a violation …

Newport Manual On The Law Of Naval Warfare, Second Edition, Newport Manual Expert Group

International Law Studies

The Newport Manual on the Law of Naval Warfare, Second Edition, is a continuing effort to restate the law of naval warfare as a purely lex lata exercise. Like the first edition of 2023, it is designed to provide a practical guide for commanders and seafarers, lawyers and officials, and educators and students. In doing so, the Manual includes developments in warfighting technologies in recent decades, which have significantly influenced the nature of war at sea. This second edition has been edited by four of the original authors following an extensive review and revision process.

Safeguarding Submarine Cables And Pipelines In Times Of Peace And War, Raul (Pete) Pedrozo

International Law Studies

Incidents involving damage to undersea infrastructure illustrate the vulnerability of submarine cables and pipelines. While damage can occur accidentally in peacetime, recent incidents suggest cables and pipelines are being systematically targeted and that the resulting damage is not accidental or the result of poor seamanship. Most undersea infrastructure can also be attacked as a military objective in wartime. Peacetime adversaries or opposing belligerents during an armed conflict can easily damage undersea infrastructure to further their political, strategic, or wartime objectives. These incidents also highlight the inadequacy of coastal State authority under international law to take measures against foreign-flagged vessels intentionally …

Maritime Incidents In The South China Sea: Measures Of Law Enforcement Or Use Of Force?, Aurel Sari

International Law Studies

China has sought to extend its control over the South China Sea at the expense of neighboring countries. In pursuing its goals, Beijing adopts a “power and law” approach, claiming extensive territorial and maritime rights in contravention of the UN Convention on the Law of the Sea and asserting these rights through coercive action in disputed waters. A key element of China’s strategy involves the use of coast guard and maritime militia vessels in an effort to portray its operations as measures of law enforcement, rather than displays of coercive power.

This article argues that the Chinese narrative of law …

Narrowing “The Gap”: Counter Gray Zone Operations, Raul (Pete) Pedrozo

International Law Studies

China is exploiting "The Gap" by conducting provocative Gray Zone operations to challenge its neighbors' sovereignty and sovereign rights, as well as their navigational rights and freedoms, in waters off their coast in the East China Sea, Taiwan Strait, and South China Sea. By engaging in malign activities that fall below the threshold of an "armed attack," China anticipates it can incrementally advance its interests without eliciting a military response from the targeted States. Diplomatic protests and third-party dispute settlement have not convinced China to halt its aggressive behavior. This article suggests States should use non-lethal counter-piracy tactics, techniques, and …

The Defense Of Taiwan: Possible Legal Justifications, Raul (Pete) Pedrozo

International Law Studies

This article examines four possible interconnected legal arguments that can be used by the United States and its allies and partners to justify the defense of Taiwan in the event of a Chinese invasion of the island. First, the United States could recognize Taiwan as an independent nation. Second, the three joint communiqués between the United States and China are premised on an understanding that the Taiwan issue will be resolved by “peaceful” means. A Chinese invasion of Taiwan would certainly breech that understanding and allow the United States to recognize Taiwan as a sovereign State. Third, a Chinese invasion …

Cyberspace And The Jus Ad Bellum: The State Of Play, Michael N. Schmitt, Anusha S. Pakkam

International Law Studies

This article examines how States are interpreting one aspect of the international law governing cyber activities, the jus ad bellum. The article focuses on two issues: (1) the prohibition on the use of force found in Article 2(4) of the UN Charter, and (2) the right of self-defense in Article 51. The critical unsettled question regarding the first issue is the threshold at which a hostile cyber operation can be characterized as a “use of force” subject to the prohibition of Article 2(4). Concerning the second issue, a number of unresolved questions plague the application of the right of …

“Unwilling Or Unable”, Lucy V. Jordan

International Law Studies

Critics of the unwilling or unable doctrine suggest that it could undermine the United Nations collective security system and argue that it requires an unacceptable ceding of a State’s territorial sovereignty. Increased reliance on the doctrine following the terrorist attacks of 9/11, particularly in relation to the use of force against ISIL in Syria since 2014, has caused the doctrine to face significant scrutiny. The purpose of this article is to ascertain whether the unwilling or unable doctrine has reached customary international law status. If found to be the case, the doctrine would confirm the right of States to act …

The Black Sea Grain Initiative: Russia’S Strategic Blunder Or Diplomatic Coup?, Raul (Pete) Pedrozo

International Law Studies

On July 22, 2022, Ukraine, the Russian Federation, Türkiye, and the United Nations signed a groundbreaking agreement to allow for the safe transport of grain, related foodstuffs, and fertilizer from three Ukrainian ports to global markets. Concurrently, a second (lesser known) agreement was concluded between the United Nations and Russia that would allow the unimpeded export of Russian food and fertilizer (including raw materials to produce fertilizers) to world markets. These agreements were hailed as a critical solution for the impending global food crisis and the safety and security of neutral shipping in the Black Sea resulting from the Russia-Ukraine …

Aid And Assistance As A “Use Of Force” Under The Jus Ad Bellum, Michael N. Schmitt, W. Casey Biggerstaff

International Law Studies

Although the prohibition of the use of force is a cornerstone of international law, our understanding of what constitutes a “use of force” under Article 2(4) of the UN Charter nonetheless continues to evolve. While the term was traditionally understood to mean armed force, emerging interpretations are expanding our understanding of the prohibition’s breadth. The Charter’s text, travaux préparatoires, and subsequent interpretations and practice by States, reinforced by the persuasive reasoning of the International Court of Justice, all confirm that the notion of force extends to indirect force, which includes military support provided to parties to a conflict. Yet, to …

Some Reflections On The Threshold For International Armed Conflict And On The Application Of The Law Of Armed Conflict In Any Armed Conflict, T.D. Gill

International Law Studies

This essay discusses the threshold of application of international humanitarian law (IHL) in both international (IAC) and non-international armed conflicts (NIAC). In relation to IAC it questions whether the International Committee of the Red Cross (ICRC) “first shot” approach is the most appropriate, since it opens the way for the intensification of conflicts beyond what is necessary in relation to relatively minor armed incidents and argues that the humanitarian protection clauses of IHL should be separated from the rules governing hostilities and makes a case for the application of ad bellum considerations of necessity and proportionality to act as a …

International Child Law And The Settlement Of Ukraine-Russia And Other Conflicts, Diane Marie Amann

International Law Studies

The Ukraine-Russia conflict has wreaked disproportionate harms upon children. Hundreds reportedly were killed or wounded within the opening months of the conflict, thousands lost loved ones, and millions left their homes, their schools, and their communities. Yet public discussions of how to settle the conflict contain very little at all about children. This article seeks to change that dynamic. It builds on a relatively recent trend, one that situates human rights within the structure of peace negotiations, to push for particularized treatment of children’s experiences, needs, rights, and capacities in eventual negotiations. The article draws upon twenty-first century projects that …

Double Classification Of Non-Consensual State Interventions: Magic Protection Or Pandora’S Box?, Pauline Lesaffre

International Law Studies

The classification under international humanitarian law of certain cross-border armed conflicts against an organized armed group remains controversial. More specifically, cross-border armed conflicts resulting from a non-consensual State intervention, such as the United States’ intervention in Syria (without Syrian consent) against the Islamic State, still divide legal scholarship regarding their appropriate classification. One theory argues for a single classification of non-international armed conflict between the intervening State and the organized armed group; another theory relies on a double classification of non-consensual State interventions, adding to the non-international armed conflict an international armed conflict between the intervening State and the territorial …

The Prohibition On Intervention Under International Law And Cyber Operations, Ori Pomson

International Law Studies

Given that cyber technologies have made way for attempts to influence the affairs of other States in novel and unique ways, scholars have turned to the international legal rule which is prima facie most relevant in addressing such meddling; namely, the prohibition on intervention. Moreover, there appears to be quite a wide-ranging consensus in scholarship that the prohibition on intervention applies to a broad range of cyber operations. In contrast to such scholarship, this article argues that, under the lex lata, the prohibition on intervention only applies to acts amounting to a use of force or constituting support for …

Islamist Terrorism And The Classical Islamic Law Of War, Joseph Hoelz

International Law Studies

Islamist terrorists have had a large influence on U.S. foreign and domestic policy for more than twenty years, and yet policy makers, legal practitioners, and the public know very little about what motivates these violent extremist organizations. A primary unifying principle among the various Islamist terrorist groups is their desire to return to a religiously ordered State, justified and based upon their interpretation of the Shari’a, or Islamic law. This article explores the Islamist terrorist interpretation of Shari’a law and how it generally contradicts that of mainstream Islamic scholars. The article begins with a review of the primary and secondary …

Revisiting Ad Bellum Proportionality: Challenging The Factors Used To Assess It, Yishai Beer

International Law Studies

Traditionally, international law has established a binary distinction between jus ad bellum and jus in bello. The former relates to the right to exercise military force. The latter regulates the conduct of adversaries engaged in an armed conflict. However, the prevailing legal approach doesn't accept this dichotomy. It wants to reduce war's hazards by applying the ad bellum rules, including the proportionality requirement, continuously throughout the conduct of armed conflict. To that end, it has established factors that define the essence of the continuing ad bellum proportionality requirement. This article challenges the near-unanimous consensus regarding these factors. It argues that …

Booty, Bounty, Blockade, And Prize: Time To Reevaluate The Law, Andrew Clapham

International Law Studies

This article considers the so-called belligerent rights of States in times of war. In particular it focuses on booty of war, blockade, and the capture of merchant ships and their cargo. It is suggested that, while the rules may not often be applied today, they nevertheless continue to exert a certain influence, contributing to confusion about the boundaries of the legitimate use of force and a blurring of the distinction between military objectives and civilian objects.

Considering that the UN Charter has outlawed the use of force, the article also questions why such rules concerning capture should continue to have …

The International Law Of Prolonged Sieges And Blockades: Gaza As A Case Study, Eyal Benvenisti

International Law Studies

In 2007, after Hamas’ takeover of the Gaza Strip, the area was subjected to an Israeli land siege, complemented in 2009 by a sea blockade. Since then, the already-dire living conditions in the Strip have declined consistently and the area’s dependence on external aid has grown. This essay examines the duties of a military power in imposing what is effectively a years-long confinement of people and outlines a general argument for expanding the obligations of a party that imposes a prolonged siege or blockade. I consider these obligations in light of three potentially relevant legal frameworks: the law of occupation; …

Transformative Disarmament: Crafting A Roadmap For Peace, Louise Arimatsu

International Law Studies

Notwithstanding their absence in the formal structures of power, women have engaged actively with disarmament for over a century. Their activism has been rich and complex. It is, however, not a history that is generally familiar to those outside the world of feminist activism and scholarship. This article tells the story of feminist activism and scholarship and how women have sought to overcome exclusion, marginalization, and silencing in both policy and law in pursuit of what the author describes as a transformative disarmament agenda. It is concerned not only with women’s political activism and the struggle for equal participation in …

Military Action To Recover Occupied Land: Lawful Self-Defense Or Prohibited Use Of Force? The 2020 Nagorno-Karabakh Conflict Revisited, Tom Ruys, Felipe Rodriguez Silvestre

International Law Studies

In September 2020, heavy fighting erupted between Armenia and Azerbaijan in and around Nagorno-Karabakh, a region of Azerbaijan long controlled by Armenia. After two months of military confrontations, a tripartite ceasefire was concluded, drastically altering the pre-existing territorial status quo.

The "Second Nagorno-Karabakh War" brings to light a fundamental question for international law on the use of force—and one that has received limited attention in legal doctrine. The question is this: when part of a State’s territory is occupied by another State for an extended period of time, can the former still invoke the right of self-defense to justify …

Developing International Guidelines For Protecting Schools And Universities From Military Use During Armed Conflict, Steven Haines

International Law Studies

One consequence of armed conflict, especially that of a non-international character, is serious damage done to vital societal infrastructure. Education–schools and universities–can be severely disrupted, even subject to attack. Targeting of schools may not invariably be unlawful if educational facilities are being put to military use. Such use may itself not be unlawful but it can result in schools being transformed from civilian objects into military objectives–and subject, therefore, to lawful targeting. This was a problem highlighted by humanitarian NGOs a decade ago and led to the formation, by both NGOs and United Nations agencies, of the Global Coalition to …