By 1414 the Latin church had three men claiming the papacy, each with cardinals, each recognised by different kingdoms, and no procedure for choosing between them, since the only authority competent to judge a pope was held to be a pope. The Council of Constance, summoned with the backing of the emperor Sigismund, cut the knot by asserting that a general council held its authority immediately from Christ and that everyone, including a pope, must obey it in matters of faith, the ending of the schism and reform.
That decree, Haec Sancta, is the most argued-over document in the history of Catholic canon law. On one reading it is a dogmatic definition of conciliar authority passed by a council whose own legitimacy the church accepts. On another it is an emergency measure with no doctrinal force, taken when no pope could be identified. Later popes repudiated it, the Fifth Lateran Council contradicted it, and the question is not settled among Catholic historians and canonists today.
The council did what it set out to do. Gregory XII resigned, on terms that let him convoke the council formally first and so preserve his line's claim; John XXIII was deposed after fleeing; Benedict XIII was deposed and ignored the deposition to the end. Martin V was elected in 1417, and a further decree, Frequens, provided that councils should meet at regular intervals, a provision that fell into disuse within decades.