Morality has been a key factor in naturalization. However, defining what constitutes good moral character has never been specified, leaving interpretation of the good moral character requirement to the discretion of immigration officials and judges. Based on an analysis of court cases filed by marriage migrants, this article expands our understanding of the legal interpretation of the “good morality” requirement in two significant ways. First, by examining the nature of the morality requirements applied to marriage migrants applying for citizenship, we identify that controlling sexual morality is one of the key mechanisms of gendering the path to legal citizenship. Second, our analysis questions the fairness of the judicial rulings and shows that judges are not reliable allies for immigrant spouses. South Korean judges tend to show great deference to the administrative branch and rarely rule against the decisions of the immigration officials. Further, the rulings tend to follow cultural and gendered, rather than legal, understanding of “good” wives and husbands. Ultimately, in the case of South Korea we show that that marriage migrant moral jurisprudence deviates from the developing jurisprudence that decriminalizes intimate choices and challenges the traditional gender roles within a family.