Legal Challenges of Hybrid Warfare: Accountability of Mercenaries and Private Military Companies - Acta Universitatis Sapientiae

Acta Univ. Sapientiae, Legal Studies, 14, 2 (2025) 283–304

DOI: 10.47745/AUSLEG.2025.14.2.11

Abstract. Hybrid warfare, which combines conventional and unconventional tactics and often relies on proxies, has become a defining feature of modern conflicts. This study examines its connection with international criminal law, focusing on the role of mercenaries and private military companies (PMCs). It argues that these actors are used as tools of ‘plausible deniability’, hiding accountability and complicating the enforcement of international law. After defining hybrid warfare, the paper places mercenaries and PMCs within this framework and analyses their status under international humanitarian law. Although they are usually excluded from lawful combatant status, they remain personally responsible for criminal acts. The Russo-Ukrainian war, especially Russia’s use of PMCs such as the Wagner Group, demonstrates the legal and moral challenges of identifying responsibility and prosecuting violations. The analysis reveals significant legal gaps and difficulties in proving individual responsibility, which allow mercenary actors to operate with impunity and weaken the effectiveness of international criminal law. The study concludes by proposing reforms to close these gaps, clarify legal definitions, expand jurisdiction, and strengthen accountability for both individuals and states in order to better address the threats posed by hybrid warfare to international peace and security.

Keywords: hybrid warfare, mercenaries, private military companies, international humanitarian law, international criminal law, Wagner Group, state responsibility, war crimes, deniability