Yellow-crested cockatoos (Cacatua sulphurea) is one of 435 species protected by law and of 512 endemic species in Indonesia. This study aimed to assess whether law enforcement to protect the Yellow-crested cockatoos (Cacatua Sulphurea) from extinction was maximal. This research method applied normative juridical research, in which the court decision is the primary legal material. The later decision of the East Kalimantan High Court Number 6/PID/2018/PT.SMR is the primary legal data or materials that be analyzed in this study. The results of this study assess that law enforcement to protect the sustainability of Yellow-crested cockatoos in Indonesia is still not optimal. Furthermore, law enforcement related to corporate violations that are more dangerous to the extinction of these species is still a problem that needs to be studied further. This study will contribute to law enforcement realizing that the protection of endemic species in Indonesia relies heavily on their firmness and fair decisions according to law. Socialization related to the law on the Conservation of Biological Natural Resources and Its Ecosystems to the people needs to be improved. Most likely, people are still not aware of protected species because they are on the verge of extinction or endemic. The research limitation of the study is that the study analyzes high court decisions that do not yet have permanent legal force (Inkracht). There is still an opportunity for both the convict and the public prosecutor to appeal to the Supreme Court of Cassation if the court’s decision is deemed not right.