Rē'tro-ăct'ive or Rĕt'ro-ăct'ive, a.

a. [Fr. rétroactif, Sp. retroactivo, It. retroattivo.] Fitted or designed to retroact; operating by returned action; affecting what is past; retrospective. Beddoes.

Retroactive law or statute, one which operates to make criminal or punishable, or in any way expressly to affect, acts done prior to the passing of the law.