In 395 AD, Rome split into two empires - the Western Roman Empire and the Eastern Roman Empire. Each side had a ruler in charge of it. The Roman Empire was split by Theodosius.
The First Geneva Convention (1864) is one of the earliest formulations of international law. International law is the set of rules generally regarded and accepted as binding in relations between states and between nations. It serves as a framework for the practice of stable and organized international relations.
Perhaps the first question to ask is whether in fact international law is law at all. The primary distinction between domestic and international law is that the latter often lacks an enforcement mechanism. There is no government to enforce the law, as there is in domestic situations.