The Supreme Court's Grand Bench last week upheld the constitutionality of the Civil Code provision requiring a couple to use the same surname when they register their marriage. The 10-5 ruling by the justices at the same time called on the Diet to discuss whether Japan should allow married couples to use different surnames if they so wish. The Diet should not take the ruling as an excuse for inaction and should instead start the process to change the provision by fully taking into account the inconveniences and disadvantages many women suffer under the same-surname system, even to the point of suffering an identity crisis.

The Grand Bench, composed of 15 justices, in a separate but related ruling declared that another Civil Code provision prohibiting women from remarrying within six months of their divorce is unconstitutional, suggesting that the ban should be shortened to 100 days. The six-month ban has been designed to avoid confusion over who is the father of a child born to a recently divorced woman. But the top court ruled that since under the Civil Code a child born within 300 days after divorce is deemed that of the previous husband and one born after 200 days have passed since marriage that of the current spouse, a remarriage ban longer than 100 days is irrational, noting that keeping in force such a margin to avoid confusion over the child's paternity cannot be justified in view of modern DNA technology that can determine the father of the newborn with a high degree of accuracy.

While the Diet should quickly take action concerning the six-month remarriage ban, it should go beyond the ruling and consider whether a 100-day ban is reasonable given the advance of DNA tests, which are relatively inexpensive and can be easily conducted.