\Re`tro*act"ive\, a. [Cf. F. r['e]troactif.]
Fitted or designed to retroact; operating by returned action;
affecting what is past; retrospective. --Beddoes.
{Retroactive law} or {statute} (Law), one which operates to
   make criminal or punishable, or in any way expressly to
   affect, acts done prior to the passing of the law.