Currently in WA hotel quarantine is also under WA's Emergency Management Act 2005
All international and some domestic travellers to Western Australia issued a Centre Quarantine Direction under the Emergency Management Act 2005 will need to quarantine in a hotel for 14 days following arrival. The quarantine period means you must stay in your designated hotel room even if you are feeling well. When you are in quarantine you are not permitted to have any visitors, even if they are another traveller also in quarantine.
Frequently asked questions about paying for hotel quarantine in WA
www.wa.gov.au