unwritten law

American  

noun

1. a law that rests for its authority on custom, judicial decision, etc., as distinguished from law originating in written command, statute, or decree.

2. the unwritten law, the supposed principle of the right of the individual to avenge wrongs against personal or family honor, especially in cases involving relations between the sexes: sometimes urged in justification of persons guilty of criminal acts of vengeance.

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unwritten law British  

noun

1. the law based upon custom, usage, and judicial decisions, as distinguished from the enactments of a legislature, orders or decrees in writing, etc

2. the tradition that a person may avenge any insult to family integrity, as used to justify criminal acts of vengeance

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unwritten law Idioms  

1. An accepted although informal rule of behavior, as in It's an unwritten law that you lock the gate when you leave the swimming pool. [Mid-1400s]

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Etymology

Origin of unwritten law

First recorded in 1635–45

Example Sentences

There’s an unwritten law that literary fiction set in the high plains be sturdy and simple — sentences firm as fence posts, commas hammered in as clean as barn nails.

From Los Angeles Times • May 31, 2024

Experts say the unwritten law of the sea is a Hollywood-fed myth and a relic of Victorian-era chivalry.

From Seattle Times • Dec. 15, 2023

Patty is Allison's next-door neighbor, and per the unwritten law of sitcoms, one might assume that the two would automatically be friends, if not best pals.

From Salon • Jul. 18, 2021

“I have the unwritten law on my side,” Manion tells Biegler, but Biegler explains that the “unwritten law is a myth.”

From New York Times • Jan. 21, 2021

It was unwritten law in China, so my informant told me, that when one man saved another’s life he became responsible for that life to the end of its existence.

From "Travels with Charley in Search of America" by John Steinbeck