In this article, attention is focused on the origin of the institution of the “reviviscence” of legal norms, which occurs in the jurisprudence of higher Courts. According to the Spanish Language Dictionary, the meaning of “reviviscence” is specified as “act or effect of reviving,” and, in turn, “revive” means: “stated in reference to whom seemed to be dead.” In applying such meanings to the judicial area, and more concretely to the subject of the validity of legal norms, the article concludes that norms which have been vacated when a law is found to be unconstitutional by the Constitutional Court, only appeared to have been rescinded; therefore, the finding of unconstitutionality can be applied retroactively as long as fundamental rights are not infringed upon. Although the general principle is that a law that has been vacated can only be reactivated through the integration of its content into a new law (art 14 Law 153/1887), a law vacated by a law that has been declared unconstitutional regains validity upon execution of the decision of unconstitutionality.