Ernst Dijxhoorn is Assistant Professor at Leiden University's Institute of Security and Global Affairs (ISGA). His research focusses on the nexus of international law and contemporary war and warfare, with a particular interest in how non-conventional and 'non-obvious' forms of warfare confront established legal categories.

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Ernst Dijxhoorn is Assistant Professor at Leiden University's Institute of Security and Global Affairs (ISGA). His research focusses on the nexus of international law and contemporary war and warfare, with a particular interest in how non-conventional and 'non-obvious' forms of warfare confront established legal categories.

He previously worked on the ESRC- and DSTL-funded project SNT Really Makes Reality: Technological Innovation, Non-Obvious Warfare and the Challenges to International Law, whose findings he developed in the co-edited Routledge Handbook of War, Law and Technology (with James Gow, Rachel Kerr, and Guglielmo Verdirame, 2019). His monograph Quasi-state Entities and International Criminal Justice: Legitimising Narratives and Counter-Narratives (Routledge, 2017) sets out his account of how unrecognised armed actors construct and contest legitimacy in statehood conflicts. With James Gow and Funmi Olonisakin he co-edited Militancy and Violence in West Africa: Religion, Politics and Radicalisation (Routledge, 2013). He did extensive fieldwork in South Sudan, Lebanon, and Kenya. Adjacent work on contested-territory diplomacy and on the legitimacy of armed groups has appeared in The Hague Journal of Diplomacy and other outlets.

In 2026 Dijxhoorn is among the conveners on the Leiden University side of NEXT GEN: The Hague Security Conference (27–28 May 2026), the inaugural edition of an annual gathering organised jointly with the Atlantic Commission and the Clingendael Institute.

Dijxhoorn obtained his PhD in War Studies from King's College London in 2014 and holds an MA in International Peace and Security (King's) and an LLM in International Public Law (University of Amsterdam). Before joining ISGA he taught in the Department of War Studies at King's, and held visiting positions at the Dickson Poon School of Law and at Royal Holloway, University of London. 

Dijxhoorn’s main interest lies in teaching all aspects of contemporary armed conflict to graduate and post graduate students. He convened the Minor in Global Affairs and was the director of the MSc Crisis and Security Management for four years, he currently  contributes to the BSc Security Studies and the MSc Crisis and Security Management programmes.