As state and local anti-discrimination provisions become more and more comprehensive, physicians who refuse to treat patients for reasons of sexual orientation or marital status are beginning to face legal liability. Increasingly, physicians are invoking codes of medical ethics alongside more familiar constitutional law claims in support of their claim to insulation from legal liability. This Article explores what medical ethics has to say about physicians who, for sincerely held religious reasons, refuse to treat patients for reasons of sexual orientation or marital status. The issue is explored through the lens of a case recently decided by the California Supreme Court in which infertility physicians refused to help a lesbian couple have a child with the aid of artificial insemination. Through a close examination of the provisions of medical ethics codes and the arguments based on those codes raised in the California case, this Article concludes that medical societies should not support carving out an exception from anti-discrimination laws for physicians who, for reasons of religious conscience, want to express their class-based biases in the clinic.