What counts as a licence under the Act
Section 15AA applies to a provider of a regulated interactive gambling service. The provider commits an offence unless it holds a licence, however described, under a law of a State or Territory that authorises that kind of service. Wagering licences from the Northern Territory and the ACT are of that kind.
For casino games the question never arises: they are prohibited under section 5, and no licence can authorise a prohibited service.
Why an overseas licence does not count in Australia
An offence under section 15 turns on the service having an Australian-customer link, which means any customer being physically present in Australia. The Act extends to acts and omissions outside Australia, and it applies to a provider whatever licence it holds elsewhere.
The Act lists what a provider can do to show it did not know about an Australian customer: telling customers that Australian law prohibits the service, binding them by contract not to use it from Australia, and examining their personal details and network data. A licence number in a footer is not on that list.
What an Australian licence gives a customer
GambleAware NSW states that offshore operators are not regulated in Australia and give no consumer protection, and that only Australian-licensed services are subject to Australian laws and safeguards. Several of those safeguards are tied to the licence: licensed wagering providers must honour BetStop, and they are barred from taking credit cards and digital currency.
Where Australian licences are listed
The Northern Territory Wagering Commission publishes its licensed wagering operators. The ACT Gambling and Racing Commission requires an ACT-based online sports bookmaker to hold its licence, and the Victorian Gambling and Casino Control Commission and GambleAware NSW both direct people to the ACMA register of licensed interactive gambling providers.
Questions
Does an overseas licence make an online casino lawful in Australia?
No. A casino game provided over the internet to customers in Australia is a prohibited interactive gambling service whatever licence the provider holds.
Can a State or Territory license an online casino?
The Act's list of regulated interactive gambling services, in section 8E, has no category for online casino games. A State or Territory licence can cover only the kinds of service on that list.