Abstract: In this keynote address for a conference on “The Common Good and Federalism in the Thought of Charles De Koninck” (Université Laval October 1-3, 2025), I offer a juristic interpretation of a famous idea that De Koninck proposed: misconceptions about the common good, or unwillingness to pursue the common good, threaten to create a “society of tyrants.” Drawing upon Montesquieu’s life-long obsession with ideas of plural tyranny or plural despotism, I locate the idea of a society of tyrants within the juristic tradition, explain the differing forms that plural tyranny takes in different constitutional regimes, and analyze the mechanisms that give rise to plural tyranny. I then apply these concepts to De Koninck’s contrast between genuine confederation, on the one hand, and a totalitarian “Grand État” on the other.