ex post facto

American  

[eks pohst fak-toh] / ˈɛks ˌpoʊst ˈfæk toʊ /

adverb

1. from or by subsequent action; retroactively; subsequently; retrospectively.

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adjective

1. having retroactive force; made or done subsequently.

   an ex post facto law.

ex post facto British  

/ ɛks pəʊst ˈfæktəʊ /

adjective

1. having retrospective effect

   an ex post facto law

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ex post facto ¹ Cultural  

1. An explanation or regulation concocted after the event, sometimes misleading or unjust: “Your ex post facto defense won't stand up in court.” (See ex post facto law.) From Latin, meaning “after the deed.”

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ex post facto ² Cultural  

1. A descriptive term for an explanation or a law that is made up after an event and then applied to it: “The chairman's description of his plan sounds like an ex post facto attempt to justify an impulsive action.” Ex post facto is Latin for “from after the deed.”

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Etymology

Origin of ex post facto

First recorded in 1625–35; from Latin: “from a thing done afterward, from what is done afterward”

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Example Sentences

See Examples For:

ex post facto

The effects have been so strong that the Fed, in a heroic feat of ex post facto rationalization, has begun to think of asset prices as another transmission mechanism for its balance-sheet policy instrument.

From The Wall Street Journal ● Apr. 21, 2026

The issue is not just to admit, ex post facto, that we were wrong, but to think more deeply about why we were wrong.

From Salon ● Dec. 20, 2025

“This is a violation of the ex post facto clause of the constitution,” said Neama Rahmani, president of West Coast Trial Lawyers.

From Washington Times ● Feb. 10, 2023

As anyone who’s ever seen a horror movie knows, ex post facto explanations of the monster’s pathology are beside the point.

From Washington Post ● Jul. 15, 2022

Because Wayna Qhapaq had not actually married Washkar’s mother—the union was properly incestuous but not properly legitimate—the new Inka demanded that his mother participate ex post facto in a wedding ceremony with his father’s mummy.

From "1491" by Charles C. Mann

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