Episode 34 – Chris O’Meara on Necessity and Proportionality

In this episode I speak Chris O’Meara, Lecturer at Exeter University Law School, about his new book, Necessity and Proportionality and the Right of Self-Defence in International Law. Chris describes his novel taxonomy for dividing the principle of necessity between general and specific necessity, and his blending the quantitative and teleological approaches to the principle of proportionality, and goes on to explain how the relationship among necessity, proportionality, and imminence should be properly understood. We delve into some of the more potentially controversial claims he makes, such as: on how he thinks necessity operates as a limiting principle; why the gravity threshold for armed attack should be lowered; whether the principles of self-defence are modified in responses to non-state actors; why the assertions and actions of a minority of powerful states, particularly in relation to clearly unlawful uses of force, and the corresponding silence of other states, should be considered so heavily in thinking about custom – and so much more! A fascinating conversation.


Necessity and Proportionality and the Right of Self-Defence in International Law (2021).

– “The Relationship Between National, Unit and Personal Self-Defence in International Law: Bridging the Disconnect,” 4 Journal on the Use of Force and International Law 273 (2017).

– “Reconceptualizing the Right of Self-Defence Against Imminent Armed Attacks,” 9 Journal on the Use of Force and International Law 278 (2022).

Recommended Reading:

– Craig Forcese, Destroying the Caroline: The Frontier Raid that Reshaped the Right to War (2018);

– Tom Ruys et al., The Use of Force in International Law: A Case-Based Approach (2018);

– Jay Kristoff, Nevernight (2016).

Episode 16 – Terry Gill on the Use of Force Against Non-State Actors

In this episode, I speak with Terry Gill, the Professor of Military Law at the University of Amsterdam, Center for International Law, and the Netherlands Defence Academy, and also the Director of the Netherlands Research Forum on the Law of Armed Conflict and Military Operations (LACMO). We discuss his recent article (co-authored with Kinga Tibori-Szabó) on the use of force against non-state actors (NSAs) within the territory of states that that are not substantially involved with, or exercising significant control over, the NSA, but which also do not consent to the use of force against the NSA within their territory – a familiar but still hot subject of ongoing debate. Terry explains why a strict understanding of the principle of necessity should be at the center of the analysis of these issues, and thus offers some perspectives on the so-called unwilling or unable doctrine that are quite different from others who support the right to use force against NSAs. We also revisit his much earlier work on the Nicaragua v. USA judgment of the ICJ, and how its formulation of attribution should be understood in this context.


“Twelve Key Questions on Self-Defense Against Non-State Actors,” 95 International Law Studies 468 (2019) (with Kinga Tibori-Szabó).

Reading Recommendations:

– Kinga Tibori-Szabó, Anticipatory Action in Self-Defence (2011).

– Sir Humphrey M. Waldock, “The Regulation of the Use of Force by Individual States in International Law,” 81 Hague Academy of International Law Lectures (1962).

– Jack Vance, Suldrun’s Garden: Lyonesse Trilogy Vol. 1 (1982).