In this ePaper, Mara Ebbers asks which options are available for third states under the law of neutrality. In a theoretical discussion of the application of neutrality law, Ebbers rejects the theories of compulsorily applicable, qualified, and obsolete neutrality due to their conceptual flaws and inadequate incorporation of the emergence of a third option for third states. Based on Rebecca Ingber’s work and the guidance of Andrew Clapham and Evelyne Schmid, she argues that third states are not — and have never been — under an obligation to stay neutral in an international armed conflict.
By analysing the state practice and opinio juris of Austria and Germany in the Russo-Ukrainian war, Ebbers illustrates how customary neutrality law is changing and how harmful the related legal uncertainty is for states. To contribute to more legal clarity, she continues to describe the options available for third states in detail — neutrality, non-belligerency, co-belligerency, and their illegal counterparts.
Ebbers concludes that, “especially in a time of declining multilateralism and more international (armed) conflicts, a multilateral agreement on neutrality and non-belligerency is essential for third states and belligerents. The answer to declining multilateralism can only be increased attempts to act multilaterally.”
This ePaper, The Shifting Concepts of Neutrality and Non-Belligerency in the 21st Century, is based on Mara Ebbers’ master’s dissertation, which was awarded the Mariano Garcia Rubio Prize for the best Master’s dissertation in international law in September 2025.
Apart from a Master’s in International Law from the Geneva Graduate Institute, Mara Ebbers holds a Bachelor’s in International Relations from Dresden University of Technology. Her research interests include International Humanitarian Law, Human Rights, and jus ad bellum. She has gained experience as a research assistant at the International Law Commission as well as in several German governmental and research institutions. Following her research on statelessness law, she joined UNHCR as a statelessness fellow with the Carlo Schmid Program.
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The applicability of neutrality law is a contested area of modern international law. Because it determines the options third states are facing in an international armed conflict, the Russo-Ukraine war lends it new urgency. This ePaper analyses these options from a conceptual and practical perspective. First, it theoretically discusses the applicability of neutrality law, rejecting the theories of compulsorily applicable, qualified, and obsolete neutrality based on their conceptual flaws and inadequate incorporation of the emergence of a third option for third states. It embraces optional neutrality based on the finding that it has always been optional. The second part examines the changing customary neutrality law and the related legal uncertainty for states. It finds that this uncertainty reproduces itself and is reflected in the German and Austrian debates and their opinio juris. To encounter this legal uncertainty, the third part details the options available for third states — neutrality, non-belligerency, co-belligerency, and their illegal counterparts.
How to cite:
Ebbers, Mara. The Shifting Concepts of Neutrality and Non-Belligerency in the 21st Century: A Legal Analysis with Focus on the German and Austrian State Practice. Graduate Institute ePaper 60. Graduate Institute Publications, 2026. https://doi.org/10.4000/15vlm.
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