A NSW sperm donor has been deemed by the High Court to be the legal father of a girl, preventing her moving to New Zealand with her mother without his consent.
The case has its beginnings in late 2006, when Robert Masson and Susan Parsons (their court pseudonyms) agreed to have a child through artificial insemination.
Mr Masson agreed on the understanding he would act as a parent, provide financial support and financial care.
He is named as the girl's father on her birth certificate and was actively involved in the girl and her younger sister's life, with both calling him "Daddy".
Issues arose when the mother and her female partner wanted to move across the Tasman with the girls.
Mr Masson stopped them through the Family Court as he was found to be a parent, but on appeal NSW state laws were used to rule him as purely a sperm donor.
The girl's mother and her partner argued NSW law clearly spelled out rules for fertilisation procedures with respect to same-sex couples.
However, Solicitor General Stephen Donaghue QC successfully argued in the High Court in April that the commonwealth definition should be used.
"State law is just not relevant," he told the court.
The argument was put that under commonwealth law Mr Masson is considered a parent, as he is the biological father and is involved in the child's life.
A majority of the High Court agreed, saying in a judgment on Wednesday no reason had been shown to doubt the initial court conclusion that Mr Masson was a parent of the child.
"To characterise the biological father of a child as a 'sperm donor' suggests that the man in question has relevantly done no more than provide his semen to facilitate an artificial conception procedure on the basis of an express or implied understanding that he is thereafter to have nothing to do with any child born as a result of the procedure," the judges said.
"Those are not the facts of this case."
The High Court decision reinstates the original Family Court orders that the women should consult with Mr Masson about parenting decisions, that he make day-to-day decisions on the children's welfare when they're in his care and that the children cannot live in New Zealand without his written consent.
Australian Associated Press