The relocation of the Nusantara Capital City (IKN) to the archipelago opens up significant opportunities to support equitable development but also presents challenges in harmonizing authority between the IKN Authority and the East Kalimantan Regional Government. This research will examine two main issues. First, the reason for the administration of the government in the Capital City of the Archipelago is carried out by the Authority Institution. Second, what are the implications of the establishment of the IKN Authority on the structure and authority of the regional apparatus of East Kalimantan Province. This study is expected to provide an in-depth understanding of the changes that occur and their impact on local government. The research method used is Normative Juridical research by examining the applicable legal rules related to the establishment of the IKN Authority and how these rules affect the structure and authority of the regional apparatus of East Kalimantan Province. In this research, the author uses several types of approaches to broaden insight, sharpen analysis, and focus on the problems studied, namely the statutory approach, conceptual approach, and comparative approach. This study aims to examine the reasons for managing the government of the Capital City of the Archipelago through the Authority Institution and its effect on the structure and authority of the regional apparatus of East Kalimantan Province. The implementation of the IKN government is carried out by the Authority which acts as an extension of the central government, allowing flexibility in the management and structure of the IKN area. The IKN Authority and the East Kalimantan Provincial Government have different but complementary authorities. To avoid conflicts due to potential overlapping policies, clear coordination and harmonization are needed so that both parties can carry out their duties effectively.