Common law.
Codified legislation
A codified law.
There is no such codified law that I am aware of.
law of nations
A government is not codified and cannot be codified. What can be codified is the law. There was not anyone who unified the Roman Empire because the Roman empire was never divided. Maybe you have in mind Justinian I who commissioned the Corpus Juris Civils (Body of Civil Law) also known as the Justinian Code. This work codified Roman civil law.
It is a change in a codified law.
Tribonian
he is justinian
Probate law is now codified (by statutory law) in most jurisdictions but it is derived from common law.
Arkansas Code
This is called common law.
This is called common law.