The father, who cannot be named for legal reasons, filed a claim against the Catholic Archdiocese of Melbourne and Cardinal Pell.
He claims to have suffered nervous shock after learning of allegations Cardinal Pell sexually abused his now-deceased son in the mid-1990s.
Cardinal Pell, who died in January, had five convictions for abusing the man's son and another boy overturned by the High Court in 2020.
He always maintained his innocence.
The Catholic Church tried to be excused from proceedings by relying on the Ellis defence, arguing the father could not sue because he was not the direct victim of the alleged abuse.
The church could use the defence until it was abolished in 2018 by the Victoria's Legal Identity of Defendants Act.
In August 2022, Justice Michael McDonald ruled that the law allowed claims from secondary victims, including the boy's father.
"The plain meaning of the words 'founded on or arising from child abuse' ... includes a claim for nervous shock brought by a parent of a child alleged to have been sexually abused," he ruled.
But in a challenge to the Court of Appeal on Tuesday, Georgina Costello KC argued for the right to appeal that finding.
She said relevant legislation did not define what a plaintiff in a child abuse case was, but did define child abuse by reference to "a person" and "the person".
She argued it was a person who, falling under the definition of child abuse, was the class of person who could be a plaintiff and no one else.
Further reference to potential defendants as being "liable for child abuse" reinforced that the law was confined to acts against a person who was themselves subject to child abuse, Ms Costello said.
But Andrew Clements KC, for the father, said the Archdiocese's case held no real prospect of success.
He said the legislation's repeated use of the phrase "arising from child abuse" was an unsurmountable obstacle for their challenge.
"Even if we had no other good points, and we would submit that we do, the repeated use of that phrase is sufficient reason not to grant the appeal in this case," he said.
The three appeal justices have reserved their decision.
The father, known as RWQ in court documents, has claimed the Catholic Church was vicariously liable for his son's alleged abuse at St Patrick's Cathedral when he was 13.
He says he suffered financial loss because of medical expenses and a loss of earning capacity because of his suffering from several psychological conditions.
1800 RESPECT (1800 737 732)
National Sexual Abuse and Redress Support Service 1800 211 028
