‘Authority to use force’ has been a subject of contentious debate, not least among the academics, politicians and lawyers, since the oft-occurrence of use of armed forces by non-state actors and terrorist groups in modern world. Since 9/11 terrorist attacks, most use of force by non-state actors and terrorist groups, which occurred primarily in Muslim majority states, have been categorized as acts of terrorism. This categorization has been made without any rational or sound scrutiny of such use of force and accordingly resulted in controversies. This article is a historical, legal and political account of Islamic international law on the use of force. It defines and interprets the fundamental principles of use of force in Islamic international law, such as jihad, and analyses the significance of those principles in scrutinizing legal and political authority to use force at the state level and inter-state level.