It does depend on the flag of the carrier as to the rules under which they operate.

NZ may have changed (I have not researched it) but I do recall when Ansett were entering the market there, they were embroiled in whether their aircraft were 'ships' so they could serve alcohol - but that was a long time ago. Royal Brunei used to allow the consumption of BYO.

In relation to AU, there are CASA regulations which prohibit the boarding of an aircraft intoxicated, refusing to comply with crew direction and interfering with the operation of an aircraft, all of which may be used in the management of intoxicated passengers.

There are no licensing rules or requirements I could find from several hours of research. There are internal airline policies, which include responsible service of alcohol standards.

Aviation law is not my field of expertise, but I did consult with a friend of mine I graduated with who is an aviation law specialist and he confirmed my research.

I am always happy to be proven wrong and pointed to a more correct answer, but in Australia, or with Australian flagged aircraft, the rules around alcohol supply and sale are airline policy, not law.