Western Australia's premier is declaring a major victory in the state's legal battle with Clive Palmer after a Federal Court judge endorsed its hard border closures as the best way of preventing the potential import of coronavirus.
But the saga is far from over with the High Court ultimately to determine Mr Palmer's claim that the restrictions are unconstitutional.
Justice Darryl Rangiah delivered his reserved decision on Tuesday after being tasked with establishing key facts in the dispute.
He ruled against WA's argument that the case should be vacated in light of the Commonwealth withdrawing its support for Mr Palmer's position.
But in a boost for the state, Justice Rangiah found that the hard borders were stronger than any alternative approach to keeping COVID-19 out of the state and that an uncontrolled outbreak could have "catastrophic" health consequences.
"This is a comprehensive victory for Western Australia and for the people of this state," Premier Mark McGowan said of the verdict.
"We have had to fight Clive Palmer and we had to fight the Liberal Party in relation to our borders and this has been a vindication of the stand we have taken."
The premier reiterated calls for Mr Palmer to drop the challenge, saying he was confident the High Court would also rule in the state's favour.
Prior to withdrawing its involvement in the Federal Court matter amid political backlash, the Commonwealth had advocated for the introduction of a "hot spot" regime which banned arrivals from designated problem areas.
Justice Rangiah found that such a plan would be less effective than the existing border closures.
He noted that WA's restrictions did not eliminate the potential import of COVID-19 since they exempted some travellers.
But the daily number of people entering the state had fallen from around 3500 in March to about 470, meaning the controls had a "very substantial effect" of reducing the likelihood of importing the virus.
Justice Rangiah said if the border restrictions were completely removed, the probability of COVID-19 being imported from anywhere in Australia was high.
Victoria was assessed as high probability, NSW moderate and Queensland uncertain due to recent outbreaks, while other states and territories were deemed low or very low.
If a person entered WA while infectious, there was at least a moderate probability of uncontrolled outbreaks with potentially lethal consequences, the judge said.
WA would also be unable to safely manage placing all arrivals into mandatory hotel quarantine.
Justice Rangiah said a "precautionary approach" should be taken given the potentially serious consequences of the virus spreading.
The matter is expected to be heard in the High Court in October.
Federal Attorney-General Christian Porter said the findings were "entirely consistent" with the Commonwealth's support of travel bubbles for jurisdictions with low case numbers.
He noted that the judgment did not take into account economic or social impacts or address the issue of constitutionality.
Justice Rangiah earlier ruled against WA's claim that retaining the Commonwealth's expert testimony would prejudice the state. He said the evidence was likely to still be raised so there was no point in having a new hearing.
Mr Palmer launched his border challenge after he was denied an exemption to enter WA.
It later emerged he had offered to withdraw the case if arbitration hearings relating to his almost $30 billion damages claim against the state were relocated.