Andrew Sullivan quotes the Catholic catechism to the effect that it can be morally permissible to discontinue medical procedures that prolong life but “are burdensome, dangerous, extraordinary or disproportionate to the expected outcome,” and that the decision should be made by the patient or, if he is unable, by “those legally entitled to act for the patient.” Death may be accepted—but not willed. All of this is an accurate rendering of Church teaching. I would add only that cutting off food and water from someone is pretty clearly willing death: the end of the action is to cause death, not, say, to avoid the pain that would come with surgery. As such, it is pretty clearly condemned.