ex post facto

adjective

Retroactive.

“What he did was not a crime when he did it, but he was convicted ex post facto.”

Meanings

adjectiveex post facto (not comparable)

alternative expost facto · alternative expostfacto

  1. not comparableRetroactive.
    1 more example

    One of them added that it was hard lines that there wasn’t any gentleman “such-like as yourself, squire,” to show some sort of appreciation of their efforts in a liquid form; […] The opportunities of acquiring an abnormal thirst had been here limited; a noble use of them had, however, been made, and again I was compelled to deal with the result in an ex post facto manner.

    1897, Bram Stoker, Dracula
    1. not comparablelawFormulated or enacted after some event, and then retroactively applied to it.

      Coupled with the Constitution's proscription of ex post facto laws is a similar prohibition against bills of attainder.

      1998, Daniel E. Troy, Retroactive Legislation, page 56
      1 more example

      That the tax would take effect after some of the payments were made also raises issues. Says former Attorney General Richard Thornburg, also in an e-mail: "Such legislation could well run afoul of constitutional restrictions on bills of attainder, ex post facto laws, laws impairing the obligations of contract, unauthorized takings of property and the like."

      2009 March 21, Jim McTague, “Would a Tax on Bonuses Be Constitutional?”, in Barron's
adverbex post facto (not comparable)

alternative expost facto · alternative expostfacto

  1. not comparablelawBy retroactive application of a law formulated or enacted after the deed in question.

    What he did was not a crime when he did it, but he was convicted ex post facto.

Synonyms & antonyms

adjectiveaffecting things past

Synonym sets from Open English WordNet, CC BY 4.0.

Origin

  1. Latinex“from”
  2. Englishex post facto

From Latin ex (“from”) + post (“after”) + factō, ablative of factum (“deed”). In Latin, ex takes the ablative case, while post takes the accusative case. (See Wikipedia for a discussion of the grammatical form and usage of this phrase.)

Full word history & related roots →

Translations

Finnish taannehtiva
  • taannehtivaformulated or enacted after some event, then retroactively applied to it
Hungarian visszamenőleges
  • visszamenőlegesretroactive
Polish ex post facto, ex post facto
  • ex post factoformulated or enacted after some event, then retroactively applied to it
  • ex post factoretroactive
Cite this entry
APA

ex post facto. (n.d.). In WatkinsX Dictionary. Retrieved November 5, 2026, from https://dictionary.watkinsx.com/word/ex%20post%20facto

MLA

“ex post facto.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/ex%20post%20facto. Accessed November 5, 2026.

Chicago

WatkinsX Dictionary, s.v. “ex post facto,” accessed November 5, 2026, https://dictionary.watkinsx.com/word/ex%20post%20facto.

Source: ex post facto on Wiktionary, CC BY-SA 4.0.