ex post facto

• expost facto
• expostfacto

From Latin ex (“from”) + post (“after”) + facto, ablative of factum (“deed”). Post takes the accusative case. (See Wikipedia for a discussion of its grammatical form and usage).

ex post facto (not comparable)

1. Retroactive.
   1. (law) Formulated or enacted after some event, and then retroactively applied to it.
      • 1998, Daniel E. Troy, Retroactive Legislation, page 56:

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

      • 2009 March 21, Jim McTague, “Would a Tax on Bonuses Be Constitutional?”, in Barron's:

        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."

• ex post

• Ex post facto law on Wikipedia.Wikipedia