The fall of the Commonwealth of Nobles as a result of internal political decay and the agent interference of neighboring countries was associated with the end of an era in the functioning of the judiciary in Poland. „Ancient” institutions had to give way to new ones. These, in turn, were brought by Napoleon and his modern codification. Their reception in Poland was a huge change both in social awareness and in the functioning of judicial institutions. In the content of the article in question, an attempt
will be made to briefly discuss the changes that occurred with the creation of the Duchy of Warsaw and the reception of Napoleonic regulations in the Polish judiciary. The scope of changes covered the entire judiciary, however, due to their extensiveness, this study will only discuss the order of judicial authorities, excluding the Prosecutor's Office. The introduction of new courts was associated with the liquidation of noble institutions as obsolete, and never really introduced uniformly in Poland. This study covers the issues of the legal and systemic basis for the functioning of the courts of the Duchy of Warsaw and their respective structure, with emphasis on the institution of the Court of Cassation.