This academic chapter explores the concept of hybrid threats and warfare below the threshold of war from a legal perspective. It highlights how hostile measures short of open conflict—including disinformation, cyber operations, economic coercion, and political interference—are used to destabilize opponents without triggering armed war. The chapter discusses the ambiguity, non-kinetic methods, incrementalism, and multidomain nature of such measures and how they exploit gaps in international law. It surveys key debates around the interpretation of the use-of-force rules under the UN Charter, sovereignty violations in cyber operations, and evolving state practices on hybrid threats. The chapter also notes how international law serves as a normative framework limiting certain hybrid actions, provides legal grounds for countering them, and is itself a target and instrument of hybrid threats. Examples include Ukraine’s ICJ cases against Russia, Russia and China’s joint declarations influencing international legal order, and strategic instrumentalization of law in hybrid competition. Several ongoing legal controversies are identified, such as the threshold intensity for use of force, the expansion of sovereignty principles to cyberspace, and legal disinformation challenges. The chapter situates hybrid threats in geopolitical rivalry contexts such as Ukraine conflict, Sudan civil war, South China Sea naval confrontations, and Belarus's weaponization of migration against the EU. Published by Edward Elgar Publishing on January 20, 2026, authored by Aurel Sari.

This academic chapter explores the concept of hybrid threats and warfare below the threshold of war from a legal perspective. It highlights how hostile measures short of open conflict—including disinformation, cyber operations, economic coercion, and political interference—are used to destabilize opponents without triggering armed war. The chapter discusses the ambiguity, non-kinetic methods, incrementalism, and multidomain nature of such measures and how they exploit gaps in international law. It surveys key debates around the interpretation of the use-of-force rules under the UN Charter, sovereignty violations in cyber operations, and evolving state practices on hybrid threats. The chapter also notes how international law serves as a normative framework limiting certain hybrid actions, provides legal grounds for countering them, and is itself a target and instrument of hybrid threats. Examples include Ukraine’s ICJ cases against Russia, Russia and China’s joint declarations influencing international legal order, and strategic instrumentalization of law in hybrid competition. Several ongoing legal controversies are identified, such as the threshold intensity for use of force, the expansion of sovereignty principles to cyberspace, and legal disinformation challenges. The chapter situates hybrid threats in geopolitical rivalry contexts such as Ukraine conflict, Sudan civil war, South China Sea naval confrontations, and Belarus's weaponization of migration against the EU. Published by Edward Elgar Publishing on January 20, 2026, authored by Aurel Sari.