Japan Changes Archaic Law Assigning Men Paternity Over Ex-Wife’s Child After Divorce

Revisions to the 19th-century code also mean that pregnant women are now allowed to remarry within 100 days of a divorce.
Koh Ewe
Japan's controversial paternity law, which presumes the paternity of children born within 300 days of a divorce, has finally been changed.
A mother with her child stands on the breakwater along the sand beach in Shichigahama, Miyagi prefecture. Photo: Yusuke Harada/NurPhoto via Getty Images

A landmark amendment to Japan’s Civil Code this week will see the scrapping of archaic restrictions on women’s legal rights to their children and their ability to remarry after a divorce.

The legislative changes, enacted on Saturday, come after years of debate over a controversial 19th-century paternity law stating that a child born within 300 days of their mother's divorce is presumed to belong to her ex-husband, regardless of his biological ties with the child or whether the mother had already remarried.


With the amendment, children born within 300 days of their mother’s divorce can now be legally recognized as the offspring of her new husband, if she is remarried by the time of the child’s birth. However, the 300-day rule will still apply if the woman has not remarried by the time of giving birth.

Previously, only ex-husbands were allowed to enter arbitration in order to deny paternity of a child born within 300 days of their divorce. But under the revised laws, mothers and children will now also be allowed to file paternity disputes. The eligibility period for filing such arbitration has also been extended from one year since knowing about the child’s birth, to three years. 

The Civil Code amendments, which will take effect in 18 months, aim to reduce the number of unregistered children in Japan. Since the law was introduced in 1896, many divorced women—especially those caught in domestic violence situations—have chosen not to register their children to avoid having their ex-husbands recognized as the legal father.

Unregistered children often have difficulty accessing healthcare and education, or obtaining a passport. According to a survey by Japan’s Ministry of Justice in August, 71 percent of some 800 unregistered people surveyed said they had not been registered as children because of the paternity law. 

Gender inequality remains pronounced in Japan, especially compared to other developed nations, with it ranking 120 out of 156 countries in the 2021 World Economic Forum Global Gender Gap Index. Japan is the only country in the world where married couples are legally mandated to share the same surname, and under the national household registry system, children are usually considered part of their father’s register, but not their mother’s. 

The revised code, passed in a House of Councillors plenary session, also saw the scrapping of a law banning pregnant women from remarrying within 100 days of a divorce. The timeframe was previously shortened from six months to 100 days in a 2015 Supreme Court ruling.

Initially meant to avoid uncertainty about who would be the legal father of a child born shortly after the divorce, the law has long been criticized for being discriminatory towards women.

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