ex post fucto 

lost in the mail

the letter from dad was ex post fucto

ex post fucto by mrisalreadytaken August 19, 2009

ex post facto 

a retroactive law, a law that retroactively changes the legal consequences of acts committed or the legal status of facts and relationships that existed prior to the enactment of the law.

Guy 1: I just murdered dat bitch for facing me!
Guy 2: Damn! Dat Dumb fuck Bush just laid down a law 'bout dat shit!
Guy 1: Motha fucka!
Guy 2: Shit! You is screwed--dat law is ex post facto!

ex post facto by Maynard Mann ('M' Dawg) June 21, 2006