The National Construction Code (NCC) is the regulatory document published by the Australian Building Codes Board that sets minimum requirements for the design, construction, and performance of buildings. It used to be called the Building Code of Australia (BCA) and is still often referenced by that name.
The NCC has three volumes. Volume 1 covers Class 2 to 9 buildings (commercial, multi-residential, public). Volume 2 covers Class 1 and 10 (single residential, private garages, sheds, fences). Volume 3 is the Plumbing Code.
For gate, fence, and balustrade work in Australia, NCC Volume 2 Part 3.9.2 covers balustrades, with rules on minimum height (1000 mm), maximum gap (125 mm), and resistance to imposed loads. Actual compliance is enforced at the local council level under the relevant state planning act.