This chapter begins with a brief overview of the backgound leading up to the current social context, it reviews the reputation of the U.S.—the leading democraic nation—for managing dissent and diversity. It considers the most relevant principles, doctrines and definitions before tracing the successive stages in the development of law and policy relating to conscientious objection. This leads to an outline of the present international and domestic legal framework and the related court system. The heart of the chapter then examines contemporary case law: first as regards conscientious objection in relation to the fundamental rights to the freedom of expression, association/assembly and religion/belief; then as regards the role of that principle in the context of public health, public social care, public education, national defence/asylum seekers, employment and commercial services. The chapter concludes with reflections on some of the more characteristic aspects of the law relating to conscientious objection in the U.S.