Australia and most other countries are members of conventions that provide international protection for people from those countries. Copyright owners from convention countries have the same protection in Australia as Australian copyright owners, while Australian copyright owners are protected in other convention countries (by the protection that those countries accord their own nationals).
Australia is a member of the Berne and Universal Copyright Conventions and the Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPS). The Berne Convention ensures reciprocity of protection for contracting states and automatic protection of copyright (i.e. no need to register or make an application for protection).