retroactivity

1. (law) The application of a law to events that took place before it was made.Examples: "Should the legislation pass with the retroactivity provision, the firm's percentage would apply to the amount already due the states; if not, it would apply to the amount they collect over the next 12 years."; "it must be pointed out that the distinction between retroactivity and retrospectivity, while describing a real difference in the verbal form in which retrospective law is expressed, lacks normative and practical significance."uncountableusually