An American mother locked in a bitter custody case over the six-year-old child she had with her former Irish partner has won an important ruling in her favor this week.

A U.S. appeals court ruled on Tuesday that it was a mistake that she was ever ordered to place her child on a plane to Ireland.

The tug-of-love saga began when Illinois-based Mary Redmond met Derek Redmond in Ireland. Although the couple never married, she became pregnant with her son Jack in 2006, who was born in the United States.

The family initially lived in Ireland, but the couple's relationship began to deteriorate.  Mary Redmond removed Jack to Illinois after an Irish court awarded joint custody to Jack’s father, Derek Redmond of Ballymurphy, Co. Carlow, in February 2011.

Ms. Redmond was permitted by the Irish court to remove her son from the country to settle their affairs in the U.S. on the condition that she swear under oath to return with him to Ireland by March 2011. Ms. Redmond instead remained in Illinois with her son and initiated custody proceedings in the state.

The initial finding by a federal court under the Hague Convention ruled that Ms. Redmond’s failure to return her son to Ireland after the Irish court’s judgment was unlawful, and ordered the child and his mother to return to Ireland, where the father could exercise his joint custody rights under Irish law.

Ms. Redmond and her lawyer stated their worry that if Ms. Redmond ever set foot in Ireland, she would face arrest and imprisonment for contempt of court due to her failure to return Jack in March 2011. The child’s grandmother, Peggy Redmond, accompanied him on the plane instead.

But according to NBC, Mary kept fighting to have him returned and finally this week the U.S. Court of Appeals ruled in her favor, ruling that Jack's 'habitual home' is here in the United States.

The court ruled that Jack should be returned to the United States, even as his parents continue their protracted custody fight in family court.

Yesterday, Mary's lawyers asked a judge to order Derek Redmond to return Jack to the United States. It appears that neither parent is willing to give up the fight, however.

Derek Redmond's attorney David Schaffer told the press this week that they've filed a request in the U.S. 'to register the initial custody determination made in Ireland that both parties vigorously participated in for several years. Both parties were awarded joint custody of their son in Ireland. That has not changed.'

Mary Redmond fears that any return to Ireland could have disastrous results for her case however, because having violated the Irish custody decision she  fears she'll be jailed if she returns to Ireland.

But Schaffer says that's not true. 'If she returns to Ireland she must immediately appear before the family court to make amends. Ireland has previously made it clear to the state court here that they have no desire to jail the mother of a young child,' he said.

'I respect both the federal district and appellate courts views on this, especially then-Chief Judge Easterbrook’s statement that it is time the subject be returned to the domestic relations apparatus of Illinois and Ireland, where it should have been all along,' Schaffer added.