The answer is YES and NO.

If you follow the instructions we provide, you will have a legal document detailling your wishes. Your family or appointed Agent will be able to waive it under the Doctor's nose and say Look, this is what the patient wants to happen.

But of course the Doctor is not legally obliged to follow your instructions. They will do what they think is right for the patient. If it comes to a point where they need guidence from family members, then, no-doubt your Living Will will be consulted.

Obviously with regards to organ donation, you are on much more solid ground. There would be serious ramifications for any Doctor who removed organs for donation against the written wishes of the patient.