A Co Armagh man has won a High Court battle to stop his ex-wife taking their son to live in the United States.
A judge ruled that his relationship with the two-year-old boy should take priority over the mother's desire to move back to her native America with the child.
But amid reservations about the father's past conduct, Mr Justice O'Hara also warned that any future deterioration in behaviour could lead to a renewed legal bid for permission to relocate.
He said: "In that event the very narrow margin by which this application has been refused may well change."
The father, referred to as Mr E, was appealing an earlier decision allowing the mother, Ms L, to set up home with their son in the US.
She had moved to Co Armagh after they met and wed in America.
But following the birth of their son, S, they split up and were eventually divorced amid the father's alleged unreasonable behaviour.
In a newly published judgment, Mr Justice O'Hara set out how Mr E had occasionally engaged in bouts of binge drinking, despite becoming incontinent after more than about three drinks.
"Quite why a grown man with that problem would still go out and take drink is more than difficult to understand," he said.
The court heard how the father drank heavily the night before his son's christening, resulting in a major row with Ms L over his behaviour and lack of control. It was claimed that he then responded to her backing out of attending a planned wedding event by threatening to stop her going on a trip to the US with their son.
"This threat was entirely inappropriate and suggests a man who has limited tolerance for the entirely reasonable views of others," the judge stated.
In 2013, after the couple broke up, the father allegedly sent his ex-wife an email to say he should have put as much energy into their marriage as he did into his hobbies.
Opposing his ex-wife's relocation plans, Mr E argued it would be best for their son to be raised in Northern Ireland and be cared for by both parents, despite their divorce.
Even though it would mean the mother has to remain on this side of the Atlantic against her wishes, he claimed that is secondary to the boy's interests.
Backing his case, Mr Justice O'Hara acknowledged improvements over the last year.
Regular contact between father and son has been arranged on an increasingly civilised basis, he pointed out.
The judge held that for as long as Mr E continues to behave as he has done in the last year it is not in S's best interests to have the relationship with his father "weakened" by moving to the US.
"Accordingly, I allow the appeal and refuse the mother's application to remove S from the United Kingdom," he confirmed.