Australians will soon know if Western Australia’s border closure is legally valid, in a court decision that could have broad consequences for the nation’s pandemic response.

The High Court will on Friday reveal its decision on billionaire Clive Palmer’s battle against WA’s border closures, prompted after he wasn’t allowed into the state earlier this year.

Mr Palmer’s legal team argued the closures weren’t reasonably necessary to prevent the virus entering and spreading through WA, breaching the constitutional freedom of movement.

WA said other methods of containing the virus weren’t as effective as border closures, saying there wasn’t a more serious reason than the pandemic to do so.

The states and territories all sided with WA, arguing the border closures don’t breach the constitution.

Tasmania – which is still off limits to Victorians and people from NSW – said the risk of coronavirus was unquantifiable.

“No one knows when an outbreak can happen again,” Tasmania’s solicitor-general Michael O’Farrell SC told the court on Wednesday.

WA’s borders are due to reopen to all states and territories from November 14, with some restrictions remaining for residents of NSW and Victoria.

Despite that, Mr Palmer’s legal team said the case remained relevant because WA’s announcement was “prospective and highly conditional”.

In June, High Court Chief Justice Susan Kiefel remitted part of the matter to the Federal Court for trial.

Federal Court Justice Darryl Rangiah found the border restriction was the most effective way for WA to deal with the coronavirus.