The discussion in this article focuses on the legal validity of an administrative court’s ruling from the perspective of multiple entities filing complaints against the same administrative decision. Recognizing the shortcomings of procedural regulations, the author proposes supplementing them with regulations dedicated to the joinder of parties. In the article, the author argues that in certain situations, this legal institution, common within civil proceedings, is applicable in practice, even though it derives from sources other than civil procedure. This allows for the implementation of the principle of the inviolability of a final court ruling.