Legal Dictionary of Pakistan

retroactive law.

A legislative act that looks backward or contemplates the past, affecting acts or facts that existed before the act came into effect. ( A retroactive law is not unconstitutional unless it (1) is in the nature of an ex post facto law or a bill of attainder, (2) impairs the obligation of contracts, (3) divests vested rights, or (4) is constitutionally forbidden. -Also termed retrospective law.