This study addresses the legal ramifications of performing marriages that do not adhere to the legal prerequisites for marriage, as well as the certainty of the legitimacy of interfaith unions based on actual positive legislation in Indonesia. By using suitable legal products to analyze problems, this research was conducted as doctrinal research. The present study employs analytical descriptive specifications, supplemented by primary, secondary, and tertiary legal sources obtained using virtual and library research methods, and qualitative analysis techniques for analysis. The research findings support the conclusion that there was initially a lack of strong regulation in Indonesia regarding the legitimacy of interfaith marriages, which resulted in legal ambiguity and doubt. As a result, interfaith weddings are frequently permitted within the terms of Article 35 letter a of the law governing population administration. The Constitutional Court has now issued Decision Number 24 of 2022, which declares that interfaith marriages are illegal, invalid, and cannot be registered, the court ruling that earlier approved the request for interfaith marriage registration is no longer recognized by the state, despite the fact that this clause is frequently broken, which further adds to the uncertainty. SEMA Number 2 of 2023 presently outlines the current norms surrounding interfaith marriages. It forbids judges from allowing requests for interfaith marriage registration and mandates that marriages be performed by parties who practice the same religion. Interfaith weddings lack legal validity and do not have the attendant legal ramifications because they are not permitted to be registered.