US Supreme Court established three important holdings:
1.. there is a right under the Constitution to refuse medical treatment. Does this include "life-sustaining" care? The US Supreme Court stopped short: "for the purposes of [the Cruzan] case," the Court "assume[d] that the US Constitution would grant a competent person a constitutionally protected right to refuse lifesaving hydration and nutrition."
2.. this right to refuse survives the patient's incompetence and can be exercised by an advanced directive or a surrogate decision maker.
3.. States may differ in regards to safeguards that they employ to ensure that withdrawal of treatment reflects the patient's wishes when the patient is unable to make treatment decisions. Every state is different on what courts will and will not accept.
the cruzan case was in 1990 i think, and was the first right-to-die case heard by the supreme court. so the law of the land allows one to refuse sustenance, and if one's wishes are clear, this shall be upheld even if one is totally and permanently incapacitated.
assuming that we believe mr. schiavo, and the courts have done that consistently, according to the law this is how it will be. end of story.
until we live in a theocracy, this is how it will be.
depending on whose theo it will be, i may be emigrating.