In NSW legislation largely regulates the planting, pruning, destruction and removal of trees and plants and also deals with some of the disputes. Pruning a neighbour’s tree back to the property line may not be permitted if it damages the tree, and pruning trees on your own property may be subject to restrictions – check with your council for details.
Where extensive pruning is required it is a good idea to get it done by a professional arborist – all pruning must conform to the Australian Standard for the Pruning of Amenity Trees (AS4373).