An Advance Directive is not legally binding in Scotland (whereas an Advance Decision is legally binding in England and Wales). However, if a medical decision was ever challenged in the courts, provided the Advance Decision was valid and applicable, it is likely that a judge would rule in favour of respecting it.
One of the general principles of the Adults with Incapacity (Scotland) Act 2000 is that if someone lacks capacity to make a decision for themselves and needs medical treatment, the wishes of the adult should be taken into consideration when making a decision on their behalf. So although Advance Directives aren’t legally binding in Scotland, health professionals should take them into account when deciding on how to treat you. Family and friends can also use them as evidence of your wishes.