The principle of marriage is a contract to justify the relationship between men and women, which between the two is not mahram. Viewed from a legal standpoint, marriage is a sacred and noble contract between men and women which is the legitimate status of husband and wife and is condemned to sexual relations with the aim of reaching a sakinah, full of love and virtue family. This article uses normative juridical research. Regarding legal marriage according to Article 2 paragraph (1) of Law Number 1 of 1974 concerning Marriage, each marriage is recorded according to the applicable laws and regulations. Besides that, it is associated with Article 2 paragraph (2) Government Regulation Number 9 of 1975 concerning the Implementation Regulation of Law Number 1 Year 1974 concerning Marriage which states that the registration of their marriages which according to their religion and belief except the religion of Islam, carried out by the Official Registration Officer Civil Registration and Population as referred to various legislation concerning the registration of marriages. Interfaith marriage is a violation of Law Number 1 of 1974. This can be seen in Article 1, Article 2 Paragraph (1) jo Article 8f of Law Number 1 of 1974 concerning Marriage. In the explanation of Article 1 mentioned: "As a country based on Pancasila, where the first principle is the One Godhead, then marriage has a very close relationship with religion / spirituality, so marriage not only has an element of birth / physical, but an inner / spiritual element also has an important role. Forming a happy family which is the purpose of marriage, maintenance and education is the rights and obligations of parents. Then Article 2 Paragraph (1) jo Article 8f explains that marriage is legal, if it is carried out according to the law of each religion and its beliefs, then there is no marriage outside the law of each religion and that belief.