Western Australia's Supreme Court has ordered Gina Rinehart's company, Hancock Prospecting, to pay the costs incurred by a Fairfax journalist in a legal battle over sources.

Ms Rinehart had taken action against senior Fairfax business writer Adele Ferguson.

She had tried to subpoena Ms Ferguson to produce recordings, texts, notes and emails.

Ms Rinehart's lawyers had argued the material was required for a private arbitration hearing in New South Wales.

But the subpoena was set aside by consent, with no substantive hearing, although there were five short directions hearings in chambers.

In arguing against costs, the company's lawyers said the application did not involve complexity because proceedings last year involving subpoenas served on West Australian Newspapers (WAN) and journalist Steve Pennells had resolved questions regarding media shield laws in WA.

But in her special costs order, Justice Janine Pritchard said Ms Ferguson's costs should be paid by Hancock Prospecting.

She said that while the costs were substantial, the meaning and operation of WA's shield laws did involve novel and complex questions.

The laws were tested in court last year, after Gina Rinehart brought separate proceedings against WAN and Pennells, who had written a series of articles about a legal stoush between the mining magnate and most of her children.

After a hearing in May, only the subpoena directed to WAN was being pursued by Hancock Prospecting, although the effect on Pennells and his ability to work as a journalist would have been the same.

Justice Pritchard found Pennells was protected by Western Australia's shield laws, and could not be compelled to reveal his sources.

She said the subpoena should be set aside "on the ground that it is oppressive and an abuse of process".

She found "the disclosure of the evidence would constitute a breach of a fundamental ethical obligation on Steve Pennells as a journalist".