Law of the land and Unwritten law

Law of the land noun - A phrase used in the Magna Carta to refer to the then established law of the kingdom (as distinct from Roman or civil law); today it refers to fundamental principles of justice commensurate with due process.

Unwritten law and law of the land are semantically related In some cases you can replace phrase "Unwritten law" with "Law of the land", this phrases are similar.

Unwritten law noun - Law based on customary behavior.

Law of the land and unwritten law are semantically related in law based on customs or traditions topic. You can use "Law of the land" instead a noun phrase "Unwritten law".