Vendredi 21 novembre 2025: Lizaveta Tarasevich

Résumé:

This thesis examines the legal significance of armed groups’ practice in the formation and identification of customary international humanitarian law (IHL) applicable to non-international armed conflicts. Although the issue has been widely discussed since the publication of the ICRC's 2005 Study on customary IHL, the topic has to date not been examined in a comprehensive and systematic manner.

To fill this gap, the thesis identifies and addresses the key limitations of the discussions on the legal significance of armed groups’ practice in the formation and identification of customary international humanitarian law. It does so, first, by analysing the nature of customary law as a source of law and exploring whether this analysis can shed light on the ratione personae scope of its potential contributors. Furthermore, it examines the underexplored relationship between the binding force of customary international law and the extent of actors’ participation in its formation. Finally, the thesis also assesses whether it is at all conceptually and practically feasible to accommodate the contribution of armed groups to customary IHL within the state-centric reality of international law.

In addition to clarifying the legal significance of armed groups’ contribution to customary IHL, the study offers a broader reflection on the suitability of customary law as a source of legal obligations for armed groups in non-international armed conflicts. Beyond this, in the absence of a coherent theoretical framework explaining how customary international law obligations evolve and apply to new contexts and actors beyond states, the study aims to contribute to developing a realistic account of the operation of customary international law in circumstances where its reach extends beyond states.

2025