Because sovereignty is defined as the power of an authority that has no superior and is superior to all others, this implies that this power has no limits and may regulate every kind of human activity, including religion. This chapter is an attempt to show that a specific conception of sovereignty is linked to a specific type of religious policy. We can thus find elements of continuity in the French history of the relations between State and religion. The need to regulate religion has played a major role in the construction of the French conception of sovereignty in the 17th century. This conception explains both Gallicanism and laïcité, but conversely laïcité has been an important element in efforts made by the Constitutional Council to preserve the sovereignty of the French State.