National Laws for Modifications to Your Bonnet - Fitting Your Bug Deflector
The Laws for all of Australia are covered in the following link provided. Bonnet modifications are a 'Basic Modification Without Certification'. Provided the Bug Deflector is fitted correctly according to the 11 metre visibility requirements, your Bug Deflector should comply with the Australian Laws. The shape of some bonnets and the height of the driver should be taken it to account. The materials the Bug Deflector is made from are 'softer' than the bonnet materials and the Bug Deflector is shaped to guide any impact backwards.
Please check the link provided below for the details outlined in the National Code of Practice for the specific details outlined. You can make sure you have complied with this Code when fitting your Bug Deflector.