The Supreme Court in Perth has ruled that West Australian Newspapers does not have to reveal its sources in relation to a series of stories about mining billionaire Gina Rinehart.
Mrs Rinehart took legal action against West Australian Newspapers over stories featuring her son John Hancock.
The ABC reports she was seeking access to details of communications between her son and West Australian reporter Steve Pennells.
But in a judgment handed down on Tuesday, Justice Janine Pritchard said Mrs Rinehart's subpoena should be set aside as it is oppressive and an abuse of process.
She also found "the disclosure of the evidence would constitute a breach of a fundamental ethical obligation on Steve Pennells as a journalist" and Pennells was "bound by an ethical obligation to respect and observe undertakings of confidence given to sources".
West Australian editor Brett McCarthy hailed the court's ruling as a win for all Australian journalists.
"I think it's a spectacular win for journalism - in particular, there's some very strong stuff in the judgment there which really backs up shield laws," he said.
The ABC reports Justice Pritchard will consider applications to reopen the case at a directions hearing next month.
