International law arose in the mid nineteenth century when European powers determined to codify and formalize customary law, to restrain the use of violence in armed conflict, and to create certain protected categories of people. The Hague and Geneva Conventions formed the core of the emerging laws of war and international humanitarian law. While the Conventions have been breached at times, they still form one of the most widely accepted and long-standing aspects of international law. International humanitarian law and laws of war clarify and formalize the differentiation between civilians and combatants, regular and irregular forces, lawful and unlawful combatants. While international laws attempt to make the demarcation of these boundaries as precise as possible, the realities of war always undermine and undo such delineation efforts. Recently, there have been increasing efforts to regulate these gray areas and create international laws and agencies to regulate groups that elude classification.