Before the Christopher Savoie case hit the news, Japanese commentators on the Hague Convention on international parental child abduction had already begun fretting over the completely unsubstantiated assertion that "almost all" instances of children being brought to Japan involve a Japanese mother fleeing from an abusive foreign father. Would Japan signing the convention result in them being sent back? they asked. This is not an unreasonable concern, though I doubt any of these commentators would go so far as to approve of foreign parents taking children out of Japan to escape an abusive Japanese spouse.
Most advanced nations have fairly extensive legal regimes designed to help prevent domestic violence and protect its victims. For this reason, while the Hague Convention contains an exception that says a child does not have to be returned if "there is a grave risk that his or her return would expose the child to physical or psychological harm or otherwise place the child in an intolerable situation," the prevailing view has been that this means children should not be returned to war zones, famine conditions or other extremely harmful environments — claims of domestic violence, however, should be left up to the legal system of the country from which the child was abducted, just like child custody issues.
It is debatable, of course, whether Japan or any other country deals with domestic violence adequately. There is also a growing view (including among some U.S. courts dealing with Hague cases) that the convention does not adequately provide for situations where a parent is seeking to protect herself or her children from domestic violence. Although the convention remains silent on the issue, a recent Yomiuri editorial calling for "careful consideration" of cases involving domestic violence suggests that Japan might simply apply the existing exceptions to prevent the return of children even if it does join.