The Supreme Court has made it harder for a parent in a custody dispute to seek the immediate return of a child under an international treaty to deter child abduction.

The justices ruled unanimously Wednesday that a one-year clock begins ticking when a child is taken out of its country of residence, even if the parent left behind cannot determine where the child is living. In the one-year period, the Hague Convention on child abduction gives judges little option but to return the child to its home country.

After a year, judges have more discretion and must take account of evidence that the child is settled in its new home.