/ɛks poʊst ˈfæktoʊ lɔː/ – Phrase
Definition: luật hồi tố, luật có hiệu lực trở về trước.
A more thorough explanation: An ex post facto law is a law that retroactively changes the legal consequences or status of actions that were committed before the enactment of the law. In other words, it is a law that applies to events that occurred before the law was passed and may impose new penalties or liabilities for past conduct. Ex post facto laws are generally prohibited by constitutional principles in many legal systems because they violate the principle of legality and fairness by punishing individuals for actions that were not illegal at the time they were committed.
Example: If a state legislature passes a law in 2024 that makes it a felony to drive without a seatbelt, and this law is applied retroactively to all driving incidents that occurred in 2023, that would be an ex post facto law.