A ruling by the Nagoya High Court ordering a woman to return her son to his father in the United States has been finalized, court officials said Monday.

The decision became final when the mother did not appeal. The court ruled earlier this month that she failed to comply with an international convention on child abduction and that it was clearly illegal for her to retain custody of the boy.

The parents are both Japanese. Their son was born in the United States and brought to Japan in 2016 by the mother without the father's consent.

The Tokyo Family Court had ordered the mother to return the son to the U.S. based on the 1980 Hague Convention on the Civil Aspects of International Child Abduction.

When the woman did not follow the order, the father filed a habeas corpus appeal with the Nagoya High Court's Kanazawa branch in Ishikawa Prefecture.

The branch court rejected the father's claim last November, but the Supreme Court in March overturned the ruling 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.