The Nagoya High Court ordered a woman on Tuesday to return her son to his father in the United States, saying her failure to comply with an international convention on child abductions is illegal.
The court ruled in favor of the father in a dispute between parents, who are both Japanese, over the custody of their U.S.-born son, who was brought to Japan by his mother without the father's consent in 2016.
Presiding Judge Hisashi Toda of the high court said that although the son "claims he wants to stay in Japan, he has been living in the country being largely dependent on his mother, who wields unjust psychological influence on him."
The mother had been ordered by the Tokyo Family Court to return the son to the United States based on the 1980 Hague Convention on the Civil Aspects of International Child Abduction.
But she ignored the order, prompting the father to file a habeas corpus appeal with the high court's Kanazawa branch.
The high court branch rejected his claim last November, saying, "Custody transfer would go against the son's will."
However, the Supreme Court in March overturned the ruling, saying it sees "clear illegality" in the mother's failure to comply with the order, and sent the case back to the high court.
The Hague treaty sets out rules and procedures for the prompt return to the country of habitual residence of children under 16 taken or retained by one parent as a result of failed marriages, if requested by the other parent. Japan joined the convention in 2014.