This study examines how the regulation and application of Law No. 15 of 2001 concerning Trademark on the practice of bad faith in registering trademarks as decided by the District Court with Decision No.58/Pdt.Sus-Merek/2016/ PNiaga.Jkt .St. In principle, the registration of a brand must be based in good faith. In this case if a brand has similarities in principle with a well-known brand, or another person's brand that has been registered, it can be concluded that there is registration of the brand. To respond to this, the brand law regulates that the cancellation of trademark registration in bad faith is included in Article 4 number (1) of Law No. 15 of 2001 concerning Trademarks. Through the Law on Trademarks, it is hoped that legal protection can be guaranteed for owners of well-known trademarks as well as those who first register their brands. The research method used in this research is normative juridical with descriptive research type. The data used in this study are primary data, secondary data, and tertiary data which are then analyzed qualitatively. From this case, conclusions were obtained about the need for the Panel of Judges of the Commercial Court and the Supreme Court to be more thorough in examining cases of brand cancellation claims, especially in interpreting equality in principle as an indicator of bad faith in brand registration. It is recommended that the Trademark Law be renewed, especially in the regulation of good faith and bad faith. It is important to provide the same direction and perceptions at the time of the substantive examination, to be a benchmark for the registration application for the brand to be accepted or rejected.