West Australian Premier Mark McGowan has heralded his state's High Court victory over Clive Palmer as a big win for all Australians.
The state's border closure has been upheld by the High Court, striking down Mr Palmer's argument the pandemic measure was unconstitutional.
Mr McGowan has relished the win, while having a crack at the Morrison government for initially joining the case to back Mr Palmer.
"This is a victory for the people of this state and it's a big win for all the people of Australia," he told reporters in Perth.
"The border has proven to be extremely effective in protecting the health and welfare of the people of Western Australia.
"This is a comprehensive drubbing for Clive Palmer."
Mr McGowan wants the Morrison government to explain why it had supported Mr Palmer, while federal shadow attorney-general Mark Dreyfus is demanding to know how much was spent.
The federal government withdrew from the case in August, with Prime Minister Scott Morrison saying he didn't want to cause any "anxiety" among the WA public.
The full bench announced its decision on Friday morning after two days of hearings earlier this week.
The court was asked to decide whether both WA's emergency management laws and underlying directions to close the border were invalid because they infringed the constitution.
High Court Chief Justice Susan Kiefel said the emergency laws, applied during "a hazard in the nature of a plague or epidemic", complied with all limbs of section 92 of the constitution.
Closing the border through those powers "does not raise a constitutional question", she said.
The court will provide reasonings for its decision at a later date.
States and territories have used border closures as part of their coronavirus response this year, and a decision in favour of Mr Palmer could have had broad consequences in the midst of the pandemic.
Mr Palmer launched his legal bid after being refused entry to WA in May.
His legal team argued the border closure, which is due to come down on November 14, was an overreach.
They argued while the border closure was okay to begin with, issues arose when it was not revoked once circumstances improved.
The case went to whether the hard border breaches freedom of interstate movement enshrined in the constitution.
WA argued the border closure was reasonably necessary to reduce the risk of coronavirus entering and spreading through the state, saying there was no more serious reason than the coronavirus pandemic.
Other states and territories - except for NSW - backed WA, arguing the border closure did not breach the constitution.
Mr Palmer has been contacted for comment.