jus non scriptum

The term jus non scriptum refers to unwritten law, which is primarily based on custom rather than formal legislative enactments. In Roman law, this was contrasted with jus scriptum, or written law, which included legislation and any other source based on written documents.12

Unwritten law, or custom, played a significant role in early legal systems. For instance, the English common law, which developed after the Norman Conquest, was heavily influenced by local customs before being shaped by judicial decisions and statutes. Similarly, in ancient Rome, unwritten law represented established practices and traditions that guided legal proceedings alongside written statutes and edicts. The concept of unwritten law also extends to unwritten constitutions, which rely on custom and precedent rather than a single codified document.324