What is the meaning of "EX POST FACTO"?

The term "EX POST FACTO" is a Latin phrase that translates to "after the fact." It refers to laws or events that take effect retroactively and apply to actions that occurred before the enactment of the law. In the context of legal terminology, it is often used to describe a law that changes the legal consequences of actions that were committed before the law was passed, thereby potentially altering the consequences for individuals who engaged in those actions when they were permissible.

This understanding is particularly important in legal discussions about the rights of individuals, particularly in criminal law, where ex post facto laws are generally prohibited by the Constitution in many jurisdictions, as they can lead to unfair treatment and lack of predictability in legal consequences. Recognizing this principle helps in understanding the legal landscape and the protections it affords to individuals against retroactive legislative actions.