The dynamic Australian health law professor Cameron Stewart and a physician colleague have published "Legal issues concerning withholding and withdrawal of dialysis" in Nephrology. The in-press article is available as a free download.
The article is a general overview of legal principles concerning healthcare decision making. Among these, is some good analysis of medical futility. For example: "The law does not obligate a nephrologist to provide treatment that they believe is of no benefit to the patient or that any benefit is outweighed by the burdens of the treatment . . . ."