Stylus Romanae curiae, as important element influencing, regulating and completing the practical application of the Canon-Law rules, established from the formularies and rules of Apostolic Chancery originally. The Popes took concern at first in their general central administrative and judicial bodies exercising a control not only over the application of universal rules, but also in its completing and representing even the position of director of jurisprudence. Since then Stylus Romanae curiae started to influence not only the next development of Canon-Law sicence, but significantly also the legal practice, especially in completing of gaps in the law, but also in interpretation and decision making repeating types of causes in the sense of administrative directives, respectivelly case authorities. Admitting the value of the source of law on the part of several canonists indeed made of it over time unwanted element that was eliminated by papacy only at the beginning of 20th century. The main goal of this article is to point out the conceptual definition and practical operation of stylus Romanae curiae and gradual weakining of its position in the Codex Law of the Cahotlic Church that culminated in the valid law.