Lawyers for Mr Pennells and his employer The West Australian newspaper on Tuesday laid out an argument, centred on oppression and abuse of process, for resisting subpoenas served on them by Hancock in early 2012.

Mr Pennells' lawyers say honouring the subpoenas and producing documents would breach a fundamental "tenet of journalism".

The subpoenas relate to a New South Wales-based arbitration between Mrs Rinehart's Hancock Prospecting and her estranged son John Hancock.

They compel The West Australian to handover all notes and recordings concerning Mrs Rinehart, Mr Hancock, Hancock Prospecting and the billion-dollar trust at the heart of the mining magnate's public family feud.

WA's media shield laws do not expressly cover pre-trial proceedings, like an arbitration, but Robert Anderson QC, representing the newspaper, argued they indirectly played into a broader argument about the subpoenas being oppressive.

"The shield laws here have a paramount importance that should not be ignored," he told the court.

"The laws have significance to persons who wish to provide information in confidence and not just to journalists."

Mr Anderson said it was "telling" that Hancock had not tried to get the relevant documents from Mr Hancock, who was a party to the proceedings.

But, the company had instead continued on with the subpoenas against journalists, which now include Fairfax Media business writer Adele Ferguson, who wrote an unauthorised biography of Ms Rinehart.

"There are other, cheaper, less obtrusive means to obtain the documents that are sought," he said.

Mr Anderson said there could be an inference made that the subpoenas were being used to "put pressure on third parties".

"At present no party in the arbitration has been compelled to produce documents," he said.

Mr Anderson also argued Mr Pennells would not be obliged to give evidence in the arbitration or to produce documents to be tendered as evidence and accordingly, he should not have to produce the documents now.

"It would be oppressive to cause Mr Pennells and The West Australian newspaper to produce material now, which they would not be compelled to produce in the arbitration," he said.

"Hancock Prospecting is seeking to circumvent the operation of these shield laws."

There was a "strong public interest" in protecting confidential sources, Mr Anderson said.

However, Hancock Prospecting's lawyers asserted the source was not confidential because they already knew it was Mr Hancock and questioned the level of "public interest" in the articles by Mr Pennells that had sparked the subpoenas.

"This is gossip, it's gossip concerning family," lawyer David Studdy told the court.

"It's gossip about a prominent family."

Mr Studdy said the shield laws didn't operate in relation to the arbitration and even if they did, they would not apply in Mr Pennells' case.

Mr Anderson's submission about the subpoenas being used to pressure media organisations was "baseless, it should not have been made," Mr Studdy said.

"It's purely speculative," he said.

Mr Anderson said producing the documents would be a breach of confidence and breach of a journalistic tenet.

"If these documents are produced now, the confidence in them is gone," he said.

"The consequences would be to breach the confidence of a source, and it would involve a breach of one of the fundamental tenets of journalism.

Supreme Court of WA Justice Janine Pritchard reserved her decision.

Ms Ferguson also had a brief appearance in the Supreme Court of WA on Tuesday, which was adjourned until next month.

Her lawyer Patricia Cahill said they had been "at loggerheads" with Hancock Prospecting's lawyers who refused to produce un-redacted copies of documents said to justify the relevance of the subpoenas to the arbitration proceedings.

Mr Studdy said Ms Cahill did not need any more than what had already been provided and was on a "fishing expedition".

Mrs Rinehart is the largest shareholder of Fairfax Media, the owner of this website.