Vacatio legis (Latin: absence of law) is a technical term in both canon and civil law which refers to the period between the promulgation of a law and the time the law takes legal effect.
In civil law, vacatio legis "indicates a condition of non-validity of a norm, and because there is one that is already taken and yet to come into force (for the course prescribed time, or not yet taken for ratification or otherwise processing of the application procedure), and because you know or at least perceive the need for regulation of a subject to which, during the period, there are no rules.