Yes. Although NSW does not have a specific statute governing Advance Care Directives, they are legally binding under common law (as confirmed by NSW Supreme Court in 2009), provided the person is mentally competent at the time of completing their directive and it has been made free from coercion.
The legally binding effect of an Advance Care Directive is confined to refusals of treatment. A demand or request in an Advance Care Directive for a particular form of treatment does not mean the health care provider is legally obliged to provide it. However, but it may be considered as indicating your consent to the treatment. In addition, the preferences you make in your Advance Care Directive are likely to be taken into account by anyone concerned with promoting your best interests at a time when you are unable to speak for yourself.
Please be aware that it is not possible to request or consent to voluntary assisted dying (VAD) in an Advance Care Directive or for an Enduring Guardian to do so on your behalf. It is a key feature of the VAD laws passed in all Australian states that the person must have decision making capacity at the time of requesting and accessing VAD.
The nomination of an Enduring Guardian is legally binding under The NSW Guardianship Act 1987.