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.
opinio juris (international law). In customary international law, opinio juris is the second element (along with state practice) necessary to establish a legally binding custom. Opinio juris denotes a subjective obligation, a sense on behalf of a state that it is bound to the law in question. See ICJ Statute, Article 38(1)(b) (the custom to be applied must be accepted as law).