What is Lex Non Scripta?

Legal Definition
Lex non scripta is a Latin expression that means "'law not written'" or "'unwritten law'". It is a term that embraces all the laws which do not come under the definition of written law or "lex scripta" and it is composed, principally, of the law of nature, the law of nations, the common law, and customs.
-- Wikipedia
Legal Definition
The unwritten or common law, which includes general and particular customs, and particular local Jaws.
-- Black's Law Dictionary
Legal Definition
a Latin phrase that means the unwritten or the common law.
Legal Definition
The unwritten law.
-- Ballentine's Law Dictionary