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!
by Maynard Mann ('M' Dawg) June 21, 2006
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