WASHINGTON

LAST month Japan’s prime minister, Shinzo Abe, promised that he would soon sign an international agreement requiring the return of abducted children to their home countries. Japan is among the few industrial countries that has not joined The Hague Convention on the Civil Aspects of International Child Abduction, and Mr. Abe’s statement comes after pressure from the White House, the State Department and Congress.

Proponents of the convention, which the United States signed in 1981, characterize it as a means of reunifying families. And it can be. However, in practice, it often has a dark side: in many cases children and custodial mothers are being sent back to a dangerous or abusive father from whom they fled.

Data from signatory countries show that the majority of abductors are mothers with primary or joint custody, and a majority of them report fleeing abuse. In short, many abductions are actually flights to safety, necessitated by the home countries’ failure to protect victims from domestic violence and child abuse. In these cases, rather than returning children to loving and safe parents, the convention actually reunifies children and mothers with their abusers.

Research by Jeffrey Edleson, the dean of the School of Social Welfare at the University of California, Berkeley, and his colleagues shows that courts typically order children returned to fathers known to have physically abused the mother, even though such violence is an indicator of significant risk to children.