This chapter analyzes the interplay between religious rules and State law from the angle of legal pluralism, discussing how State recognition of religious rules can affect the degree of legal diversity that is available to citizens. This issue is approached through an examination of religious law, that is rules that are considered to be different from secular rules, particularly in those legal traditions that have been more strongly infl uenced by the Christian religion. As the latter rules are frequently identifi ed with State law, religious laws are regarded as a challenge to the State monopoly of law. First, the chapter defi nes what is meant by religious rules; second, it examines the tensions between religious and secular rules; and fi nally discusses the different strategies and tools implemented and used by States to govern these tensions.