/ˌrɛtroʊˈæktɪv lɔː/ – Phrase
Definition: (Mỹ) đạo luật có hiệu lực hồi tố, đạo luật có hiệu lực trở về trước.
A more thorough explanation: A retroactive law is a law that applies to events that occurred before the law was enacted. It is a law that has a backward effect, changing the legal consequences of actions that were taken before the law was passed.
Example: The new tax legislation included a retroactive law that applied the increased tax rate to income earned in the previous year.