Scott Morrison asks Clive Palmer to drop court challenge to WA border closure

Scott Morrison has personally appealed to Clive Palmer to scrap a challenge against the Western Australian border ban, as the WA premier accused the federal government of falling short in efforts to bin its evidence helping Palmer’s case.

After two months of making submissions and supplying expert evidence calling for the border ban to be struck down, the commonwealth has withdrawn from the case under pressure from premier Mark McGowan.

Western Australia has applied for a retrial, arguing commonwealth evidence has prejudiced its case, but Palmer seeks to rely on that material to win the case, which could have implications for border bans nationwide, including in Queensland.

Related: Morrison backflips on move to strike down WA border ban with promise to 'assist' state

On Friday the federal court heard from parties about how to “unscramble the egg”. Justice Darryl Rangiah said there no was doubt that WA had been “disadvantaged by the conduct of the commonwealth”, with evidence from two expert witnesses who suggested the border ban was not necessary.

The solicitor general, Stephen Donaghue, submitted the commonwealth’s hands were tied at the hearing – because it had agreed to WA’s demand to withdraw from the case, he said it was “neither possible nor appropriate” to make further submissions on whether a retrial is necessary.

McGowan told reporters in Perth the commonwealth “unfortunately did not support WA’s application to have the case struck out”.

He said it “would’ve been better if they’d supported a fresh trial” but accepted the question is “now in the hands of the judge”.

McGowan promised to keep “fighting for our right to protect the citizens of our state”, describing this as “our a battle, in fact, our war with Clive Palmer to protect our state”.

Earlier, Morrison and the finance minister, Mathias Cormann, both made appeals to Palmer to stop the case.

“One quarrel I don’t have is with Mark McGowan, his quarrel is with Mr Palmer,” Morrison told reporters in Canberra.

“The only way out, I think, is for Mr Palmer not to proceed with the case. He’s the only one who can prevent that case from going forward. And I think that would be a good decision.”

Morrison wrote to McGowan on Thursday stating the commonwealth “does not object” to its application for a retrial and offering to support it “in any way it could outside the courtroom, having withdrawn from the proceeding at Western Australia’s request”.

As recently as 31 July, attorney general Christian Porter’s submissions had argued the WA border ban “cannot be justified”.

He also argued that “there is no basis upon which the Court could find that any outbreak of Covid-19 will or is even likely to lead to severe consequences” – because the risk of an outbreak could not be quantified and measures could stop positive cases “spreading to more than a handful of people”.

In one submission dated 8 July, the commonwealth asked the court to find that if WA imposed a 14-day quarantine on arrivals from Victoria, it might take five months to 3.34 years for coronavirus to spread to WA from that state.

It also argued there was “low if not negligible” risk of travel from Queensland, South Australia, Tasmania, the Northern Territory and the ACT.

The commonwealth has now submitted to the court that, since it is no longer a party, it no longer presses for any of the findings of fact it sought at trial.

But the WA solicitor general, Joshua Thomson, warned this “does not remove the existence of the expert evidence”. He said it was “most unusual” of the commonwealth to have gone “into battle, then seek to withdraw from the field of battle” because they have left behind a “mixed up train of evidence”.

Palmer’s counsel, Peter Dunning, argued that although the commonwealth no longer relied on that evidence, the judge could not ignore it because there is “no property in a witness” and “they don’t own their evidence” once it had been heard in court.

Related: Clive Palmer-backed court challenge to Queensland Covid-19 border closure dropped

Justice Rangiah expressed scepticism about the utility of a retrial, noting that Palmer may simply call the commonwealth’s witnesses again.

He reserved judgment for a later date, after reprimanding the commonwealth for “extremely discourteous” behaviour of informing the media before the court of its decision to discontinue its intervention on Sunday, and indicating the commonwealth would pay the costs of Friday’s hearing.

Labor’s shadow attorney general, Mark Dreyfus, said Porter had thrown the “entire weight of the commonwealth’s legal resources behind Clive Palmer’s attack on Western Australia’s border laws” in three days of hearings, including cross-examination of WA witnesses.

Dreyfus said Morrison and Porter had done a “total backflip” after they “sniffed the political wind” but “the damage has already been done”.

“Not only did the commonwealth’s withdrawal come far too late … the Morrison government is now refusing to act to undo the damage.”

Earlier, Morrison explained the commonwealth had changed its course in the case due to “substantially changed” coronavirus infection rates and “escalation of community concerns” in WA.

He suggested states should agree to a set of principles before imposing border bans, including committing to consultation and “not to act arbitrarily or indiscriminately” – an apparent reference to WA’s decision to ban visitors from states with no community transmission.