The paper strives to analyse if there is a doctrine that would help to solve issues connected with changes in legal regulation during time. If such a doctrine would exist it would help to evaluate acceptability of retroactive laws or at least would show conditions that should be met if the legislator would decide to pass the law with retroactive effect. The paper analyses some judgements of the
Constitutional Court. It concludes that in current state of law it is difficult to develop a consistent doctrine that would govern issues of temporal scope of efficiency of laws.