retroactive law
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; retroactive statute; retrospective statute. [Cases: Constitutional Law 186–196; Statutes 261–278. C.J.S. Constitutional Law §§ 390–404, 406–408, 421; Statutes §§ 407–431.]