This is an appreciative review of a classic text on medieval church-state relations by the leading medieval historian of his day, Brian Tierney. The text documents the enduring power of medieval struggles for religious freedom and for balancing church-state relations. It also documents the precocious medieval development of modern legal concepts like jurisdiction, corporations, human rights, and constitutional order. Tierney stands in the vanguard of great historians who have made the Middle Ages an essential chapter in understanding the development of the Western legal tradition.