I think this describes the case people are thinking of:
https://www.familylawincanberra.com.au/custody-of-transgender-child-lost-by-non-accepting-parents/
The parents then went on to lose an appeal.
https://www.familylawincanberra.com.au/custody-of-transgender-child-lost-by-non-accepting-parents/
The parents then went on to lose an appeal.