The Catechism of the Church is clear concerning extraordinary treatment:

2276 "Those whose lives are diminished or weakened deserve special respect. Sick or handicapped persons should be helped to lead lives as normal as possible."

2278 "Discontinuing medical procedures that are burdensome, dangerous, extraordinary, or disproportionate to the expected outcome can be legitimate; it is the refusal of "over-zealous" treatment. Here one does not will to cause death; one's inability to impede it is merely accepted. The decisions should be made by the patient if he is competent and able or, if not, by those legally entitled to act for the patient, whose reasonable will and legitimate interests must always be respected.

2279 Even if death is thought imminent, the ordinary care owed to a sick person cannot be legitimately interrupted. The use of painkillers to alleviate the sufferings of the dying, even at the risk of shortening their days, can be morally in conformity with human dignity if death is not willed as either an end or a means, but only foreseen and tolerated as inevitable Palliative care is a special form of disinterested charity. As such it should be encouraged."

Pope John Paul II clarified what constitutes a natural and ordinary means of preserving life in his address to the Participants in the International Congress on "Life-sustaining" Treatments and Vegetative State. In paragraph four we read that the term "ordinary care" is "... basic health care (nutrition, hydration, cleanliness, warmth, etc.), and ... the prevention of complications related to [one's] confinement to bed. He also has the right to appropriate rehabilitative care and to be monitored for clinical signs of eventual recovery."

Further in the same paragraph the Holy Father stated: "I should like particularly to underline how the administration of water and food, even when provided by artificial means, always represents a natural means of preserving life, not a medical act. Its use, furthermore, should be considered, in principle, ordinary and proportionate, and as such morally obligatory, insofar as and until it is seen to have attained its proper finality, which in the present case consists in providing nourishment to the patient and alleviation of his suffering." [click here to read the entire address]

Living wills should be written in a manner that fulfills the language in the Catechism, but also the spirit of the teaching of the Church. As long as they are in conformance with Church teaching living wills are allowable.