West Australian Premier Mark McGowan has accused Clive Palmer of seeking to enter WA so he can promote hydroxychloroquine as a coronavirus cure.
The billionaire mining magnate, who was denied an exemption to WA's hard border closures, is challenging the restrictions on the basis they are unconstitutional.
A ruling is expected in the High Court in October after a four-day hearing wrapped up in the Federal Court last week.
Mr Palmer has claimed he wanted to enter WA to attend to business interests and meet WA senator and Finance Minister Mathias Cormann.
But WA's premier claims Mr Palmer had other intentions when he initially submitted his application.
"He wanted to come to Western Australia to promote hydroxychloroquine to the people of the state as some sort of cure for COVID," Mr McGowan told reporters on Monday.
"All the evidence is not only is it not a cure, it's actually dangerous.
"Him coming to Western Australia to promote a dangerous drug, I don't think was a good thing for our state and I'm pleased that (WA Police) rejected him."
Mr Palmer in April announced he had purchased almost 33 million doses of hydroxychloroquine, an anti-malarial drug touted by US President Donald Trump which has since been found to be ineffective at treating COVID-19.
It also emerged on Monday that Mr Palmer's pilot had completed some of the exemption application forms on his behalf and they contained errors.
Prime Minister Scott Morrison wrote to Mr McGowan at the weekend saying the Commonwealth would no longer support the High Court case after taking into account the evolving state of the pandemic in recent months.
Having labelled Mr Palmer "Australia's greatest egomaniac", Mr McGowan said he was prepared to reconcile with the Morrison government.
"I want to get on with the prime minister, I want to work together with Senator Cormann ... this has been a pretty big road bump but we're past it now and I think relations between the state and Commonwealth should get back onto an even keel," he said.
Mr Palmer said it was "astounding" the premier and his ministers continued to publicly comment on a matter that was before the court.
"They need to respect the court's independence and as officers of the court, they need to take these responsibilities seriously,'' he said in a statement.
WA recorded no new virus cases on Monday, leaving the state with six active cases.
The premier announced $319 million in new funding for upgrades at 63 public schools across the state, the latest in a series of stimulus measures.
"These are extraordinary times and we have to use our financial capacity to get people back to work," Mr McGowan said.
"We've got to get a pipeline of investment now. We can't wait till later."