The right of healthcare professionals to decline participation in specific procedures they believe to be immoral has been an unquestioned tenet of medicine for centuries. Since the shift in medical ethics in the past generation whereby patient autonomy has become the dominant principle, this right of conscience has been challenged. It has been most directly challenged by Opinion #385 issued by the American College of Obstetricians and Gynecologists (ACOG) in November 2007. This article reviews the pertinent history of medical ethics, focusing on the right of conscience, and the ethical issue of moral complicity.