<![CDATA[mmigration plays an essential role in maintaining state sovereignty through the supervision of the movement of people entering and leaving the territory of Indonesia. One of the challenges faced is the practice of illegal fishing committed by foreign nationals in the waters of Natuna. Natuna's geographical location, which borders several neighboring countries, makes the area highly vulnerable to illegal fishing activities that not only cause significant economic losses to the state but also threaten the sustainability of marine resources and Indonesia's territorial sovereignty. In the context of law enforcement, the Directorate General of Immigration has the authority to impose immigration administrative measures on foreign nationals who violate Indonesian laws, including deportation, deterrence, revocation of stay permits, and other administrative measures in accordance with the applicable laws and regulations. This study employed empirical legal research using a socio-juridical approach. The research was conducted at the Class II Immigration Office TPI Ranai by utilizing primary data obtained through observation and interviews, supported by secondary data in the form of legislation, books, academic journals, and other relevant legal literature concerning immigration administrative measures against foreign nationals involved in illegal fishing. The collected data were analyzed qualitatively to examine the effectiveness of implementing immigration administrative measures and the factors influencing their implementation. The findings indicate that the implementation of immigration administrative measures against foreign nationals involved in illegal fishing in the Natuna region has been carried out through deportation, deterrence, revocation of stay permits, and temporary placement in Immigration Detention Houses in accordance with Law Number 6 of 2011 concerning Immigration. However, the effectiveness of these measures is influenced by several factors, including inter-agency coordination, the quality of human resources, the availability of facilities and infrastructure, the vast maritime surveillance area, the completeness of travel documents, international cooperation, geographical conditions, the level of compliance of foreign nationals with Indonesian law, and the utilization of information technology in immigration supervision. Therefore, strengthening cross-sectoral coordination, improving the capacity of immigration officers, optimizing technology-based surveillance systems, and enhancing international cooperation are necessary to improve the effectiveness of immigration administrative measures in supporting law enforcement, protecting Indonesia's fisheries resources, and safeguarding the sovereignty of the Republic of Indonesia.]]>
