Leges quae retrospiciunt raro, et magna cum cautione soot adhibendae neque enim Janus locator in legibus

Laws which are retrospective are rarely and cautiously received, for Janus has really no place in the laws. The maxim expresses the well-recognized doctrine that retrospective laws are not favored, and although they are not prohibited by the Federal Constitution, nor by the constitutions of many of the states, courts will always, where possible, give a construction which avoids a retrospective meaning. 50 Am J1st Stat § 477.