The government will on Wednesday introduce urgent legislation to parliament enabling temporary COVID-19 declarations to be made for three-month periods.
Under the new arrangement, the government would no longer be able to declare immediate border closures or require travellers to hold entry permits.
The police commissioner would retain the power to make declarations about mask-wearing in aged and disability care settings and stay-home orders for positive cases.
Opposition Leader Mia Davies said she had been informed the government wanted the legislation to pass through the lower house by Wednesday evening.
She accused the government of abusing its majority in both houses by denying the opposition proper time to scrutinise the bill.
"That's what we see again and again from this government - a contemptuous approach to the use of the parliament because they've got the numbers," she told reporters on Tuesday.
WA kept its borders closed for almost two years before finally reopening in March this year.
The existing state of emergency powers must be renewed every two weeks, with the latest set to expire on October 7.
Mr McGowan said it was the right time to move to "much lesser" powers, with the pandemic threat no longer as serious.
"A lot of people have called for this. We've listened," he told ABC Radio.
"We've drafted it as quickly as we can but we need to get it through the parliament so we can implement it when the existing state of emergency expires."
The state government is set to begin operating the newly completed $400 million quarantine centre at Bullsbrook in Perth's north.
With returned travellers no longer required to quarantine, Mr McGowan had flagged potentially using the Commonwealth-funded facility as temporary accommodation for overseas workers.
But the premier on Tuesday conceded there was insufficient demand.
"We were hoping for that but we consulted industry and they weren't that keen," he said.
"The location is way out there in Bullsbrook in the bush. The Morrison Liberal government decided to put it out there."
The centre will instead be prepared for use during disasters including bushfires.
The WA government will spend $13 million on maintaining the facility before handing it back to the Commonwealth after a year.
Other states have also grappled with how to use their own quarantine facilities.
The Centre for National Resilience COVID-19 quarantine facility in the Northern Territory closed earlier this year.
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