Ubi periculum

Ubi periculum (Latin: Where danger) was a papal bull promulgated by Pope Gregory X during the Second Council of Lyon on 7 July 1274 that established the papal conclave as the method of selection for a pope. The conclave formalized the tactics that had been adopted by the magistrates of Viterbo against the cardinals in the protracted papal election of 1268–1271, which had produced Gregory X.
Historians have suggested that Gregory X's status as a non-cardinal prior to his election caused him to adopt such a policy that de-emphasized the interests of the College of Cardinals. The goal of Ubi periculum was to limit strategic maneuvering within papal elections to produce faster outcomes, thereby reducing the number of schisms and disputed elections.
Ubi periculum also copied from the election procedures of the Dominican constitution of 1228 as well as the communes of Venice (1229) and Piacenza (1233).
The new election rules limited each...