Recent studies of the ius reformandi examine the right of reformation’s theoretical development while overlooking the process of conflict and negotiation that led to a practical right of reformation prior to the 1555 Peace of Augsburg. In October 1544, the imperial city of Augsburg installed an evangelical preacher in Mindelaltheim, a village in the Habsburg margravate of Burgau. The German king Ferdinand, who controlled high justice in the village, opposed Augsburg, arguing the city’s actions violated the king’s prerogative to regulate his territory’s religious exclusivity. Augsburg’s allies in the Protestant Schmalkaldic League agreed, and the city was forced to remove its preacher. In the process, both Ferdinand and the Protestant estates tied the ius reformandi to ownership of high justice. This represented an interim arrangement of necessity based on late medieval legal formulas that could facilitate coexistence until resolution of the religious question. The Reformation’s expansion often depended on constellations of legal rights that had their roots in the Middle Ages.