I arrived from SFO today and IIRC they made it clear to transit pax to MEL were not able to buy duty free and take it with them.

Having had the TSA goons in USA this week object to a tiny little 2 Oz bottle of Cholula hot sauce I was carrying, nothing would surprise me.

HOWEVER all Americans please note you CAN buy duty free on arrival in MEL (and SYD) before you leave customs.

I noticed this morning a litre of decent Gin was $A19 ($US14.50) so prices are pretty good. ^