A major current in recent scholarship has drawn on Machiavelli’s writings to articulate a non-sovereigntist conception of popular power. However, such interpretations have not generally offered a rigorous analysis of conceptions of sovereignty that were available in Machiavelli’s own time. In this paper, I focus on Machiavelli’s discussion of a historical episode which played a central role in classical and humanist discussions of sovereign power: the Decemvirate of 451-450 BC, an extraordinary commission created for the drafting and enactment of Rome’s legal code. Through a close reading of the Discourses on Livy, I argue that Machiavelli’s chapters on the Decemvirate comprise a miniature “treatise” on the perils of “absolute authority.” I also show that Machiavelli’s account of the decemvirs’ election contains a web of allusions to the lex regia, the “royal law” by which the Roman people was thought to have transferred all its imperium and potestas to the emperors. By illustrating the destructive consequences of the decemvirs’ grant of authority, Machiavelli poses a challenge to absolutist juridical theories built on the lex regia; moreover, he illustrates that electoral institutional arrangements can readily give rise to tyrannical power.