Authors of this thesis point to the problem of judiciary contra legem of the Czech Constitutional Court regarding the principle of legal certainity by analyzing chosen decisions of Czech Constitutional Court, in which the principle of legal certainity was relativized. Authors also try to provide a certain formula, according to which the courts should act in order to secure the principle of legal certainity on the one side and on the other side, to create space for protection of such values as good morals and decency also in cases in which the positive law does not guerentee it in the concrete legal relationship.