The children, a girl and a boy, were aged 12 and 10 respectively at the date of the court proceedings. They had lived in Canada for the majority of their lives.
On 4 July 1986 the parents entered into a separation agreement which provided for joint custody with the children residing with each parent in alternating years.
In June 1991, while the children were in her care, the mother unilaterally sought to deviate from this agreement and brought an action for exclusive custody in a California court. The children were due to be returned to the father on 1 August 1991.
On 1 July 1991 the father initiated return proceedings.