Western Australia’s tough border stance has been staunchly defended by states and territories in Clive Palmer’s High Court case, but the billionaire’s lawyer labelled it ‘obnoxious’.

Solicitor-Generals from Victoria, Queensland, South Australia, Tasmania, the Northern Territory and the ACT all intervened in the border battle.

Mr Palmer’s lawyers have questioned if the ban was “reasonably necessary”.

They believe the WA government should have considered alternative methods and opened to jurisdictions with a “low risk” of coronavirus because it would not have increased the risk to WA residents.

But ACT solicitor general Peter Garrisson SC said states and territories had experienced different levels of risk that required varied rational responses.

“The risk of spread from COVID-19 … is sufficient to warrant risk,” he said, adding that a low threat could quickly change to moderate.

“One case and the consequences for WA would be catastrophic.”

He said a precautionary approach was appropriate and any measure other than a border closure would not have met the emergency health directions – which were established to protect West Australians.

Tasmanian solicitor general Michael O’Farrell SC also told the court Mr Palmer’s argument was flawed.

He said it assumed that because less restrictive means were adopted in other jurisdictions, WA’s health direction must fail the reasonable necessity test and was therefore a prohibition.

“The issue is whether or not WA has chosen an appropriate means,” he said.

“We think it has.”

Mr Palmer’s own state of Queensland called on the court to be “slow to disturb the balance struck” by the WA government given the risks of COVID-19.

In reply, Mr Palmer’s counsel Peter Dunning QC said it had been reasonably necessary to close the border.

But the problem was that it was “not later revoked”.

“It did become obnoxious,” Mr Dunning told the court.

WA solicitor-general Joshua Thomson SC spent the morning defending the state’s approach.

He pointed to Australia’s own international border closure and New Zealand’s strict lockdown as examples that social distancing and face masks were not as equally effective as a hard border.

“The measures that have been adopted in this case are clearly the most effective and there are no other measures available,” Mr Thomson said.

He reasoned that the health and safety of the WA population was a legitimate reason for freedom to be breached to some extent.

“The burden imposed for a particular purpose is of the lowest minimum amount because constitutional freedom shouldn’t be trampled upon without justification,” he said.

“It’s hard to imagine a more serious threat than a pandemic.”

The fortnightly revision of the state’s emergency declaration was also used as evidence that the border was not a fixed prohibition.

High Court Justices will now consider the evidence but are expected to hand down a ruling soon due to the constitutional issues that could be faced by all jurisdictions.

Mr Palmer is understood to be in Canberra but did not attend the court.