Marriages that are not officially registered (sirri) cause problems in the national legal system, especially regarding the determination of the nasab and inheritance rights of children born. The Constitutional Court Decision No. 46/PUU-VIII/2010 grants civil recognition to out-of-wedlock children against their biological fathers, which juridically expands legal protection. However, this provision creates normative tension with the principles of Islamic law that emphasize the importance of clarity of nasab through legal marriage. This study aims to analyze the relevance and application of the concept of saddu dzariah in the context of the distribution of inheritance for children from unrecorded marriage. The method used is qualitative with a normative and descriptive-analytical approach. Data was collected through literature studies that included court decisions, laws and regulations, classical fiqh books, and contemporary legal literature as primary, secondary, and tertiary sources. The results of the study show that the concept of saddu dzariah plays a preventive mechanism in maintaining the clarity of the nasab and preventing the social harm (mafsadah) caused by the practice of unrecorded marriage. Although national law prioritizes substantive justice, this principle remains relevant as a moral and spiritual basis in the formation of Islamic inheritance norms that are in line with the main purpose of sharia (maqasid sharia). These findings underscore the importance of integration between positive law and Islamic law principles in building a fair and sustainable inheritance law system.