West Australian Premier Mark McGowan has doubled down on his government's all-or-nothing hard border arrangements, saying there is no way of guaranteeing people haven't recently visited coronavirus hotspots in Victoria and NSW.
Billionaire mining magnate Clive Palmer is challenging WA's border closures in the Federal Court, arguing they are unconstitutional.
His case is effectively being bolstered by evidence from the federal government, which is expected to argue that targeted quarantine measures are just as effective as state border closures in managing potential COVID-19 outbreaks.
Once the facts of the case are established, it will be heard in the High Court.
WA has tightened its border restrictions in recent weeks, denying entry to anyone from Victoria and NSW who cannot meet limited criteria.
The few workers granted an exemption must be immediately tested for coronavirus before going into quarantine.
Mr McGowan remains steadfast that WA will not allow arrivals from other states that have similarly low case numbers, including Tasmania which is proposing a travel bubble with WA, South Australia and the Northern Territory.
"People can jump from Victoria or NSW to other states without us having any control," he said on Tuesday.
"We've just kept a very, very strong arrangement in place to keep the borders closed, to make sure it's easily understood that we keep people from elsewhere out. And thus far it's worked."
WA has not recorded any community transmission of the virus since April 12.
Mr McGowan's position on the borders has put him at odds with Prime Minister Scott Morrison, with whom he has worked closely during the pandemic.
"I get on well with the prime minister. We want to work with the federal government," the premier said.
"This is a national crisis and we need to all work together irrespective of political boundaries. But them joining the High Court action is a mistake on their behalf."
The government on Tuesday announced the latest measure in its economic recovery plan, promising $167 million to upgrade TAFE campuses across the state.
It is expected to create 1000 jobs.
WA recorded one new case on Tuesday, a returned traveller in his 40s who is in hotel quarantine.
The state has three active cases.