Concentration of power in a political machine is bad; and an Established Church is only a political machine; it was invented for that; it is nursed, cradled, preserved for that; it is an enemy to human liberty, and does no good which it could not better do in a split-up and scattered condition.
There is the enormous corpus of Islamic law that is very rich. However, law is one rational exercise of reason. Philosophy is very different. Philosophy wants to try to understand everything. It is a better dialogue partner with faith than law.