In the current geopolitical environment, liberal democracies vie for influence and prosperity with autocratic governments, such as those of China and Russia. While the great powers do not shy away from using aggressive force, much of their rivalry today takes place below the threshold of armed conflict, in a conceptual and practical 'grey zone' between war and peace. Autocratic states operate in this grey zone to target the vulnerabilities of liberal democracies, creating hybrid threats that rely on instruments ranging from economic, diplomatic, legal, and informational pressure all the way to military coercion. Law plays a critical role in this context. In the ethically and legally ambiguous grey zone, international law serves as a normative, yet malleable, framework within which geopolitical rivals compete. State and non-State actors invoke the law as the source of authority, while simultaneously hoping to shape the international legal order in their own strategic interests. Hybrid Threats and Grey Zone Conflict offers the first in-depth assessment of the legal and ethical aspects of hybrid threats and grey zone conflict. It explores the responses available to democratic nations for countering hybrid and grey zone threats whilst adhering to liberal democratic values and the rule of law. Bringing together diverse scholarly and practitioner perspectives, the volume introduces readers to the conceptual and practical difficulties arising in this area, the rich debates the topic has generated, and the challenges that countering hybrid threats and grey zone conflict poses for liberal democracies. This volume is essential reading for anyone interested in learning more about contemporary forms of strategic competition below the threshold of open hostilities.