Ex Post Facto Legal Meaning and Definition

Here is a simplified definition of the legal term Ex Post Facto.

Ex Post Facto (adjective)

This is a Latin term that translates to "after the fact." It refers to laws enacted after a particular act has been committed, either making it illegal (although it was legal when performed) or increasing the penalty for that act. According to Article I, Section 9 of the U.S. Constitution, such laws are strictly forbidden. Therefore, new rules or longer sentences enacted by a state legislature or Congress cannot be applied retroactively to crimes committed before the enactment of the new laws.