The application of law is based not only on the legal text but also on some guidelines concerning its interpretation. This can lead to considerably different understanding of provisions of law which reduces legal certainty. Legal provisions on statutory interpretation may increase the uniformity of judicial practice. On the other hand they can become a tool of manipulation. This paper consists in the analysis of potential dangers related to the creation of interpretative regulations by the legislator. It also deals with the possible content of statutory rules of interpretation. One of the key questions interpretative provisions could answer concerns an impact of dynamically changing circumstances on the meaning of a provision – whether to follow historical intent or to adapt meaning to new conditions. Can the legislator impose rules on this issue? I would like to indicate the boundaries as to the content of interpretative directives so that they do not violate the separation of powers.