When he was nominated as Master of the Order at that gathering, the French contingent of the Chapter objected to him based on his alleged lack of studies appropriate to the office.

Discipline had become a major concern of Munio's predecessors, who issued frequent appeals to the friars and nuns of the Order to maintain the spirit of the Rule.

In his first letter to the Order at large after his election, Munio issues a serious call to the friars and nuns to keep a spirit of poverty more strenuously, as well as an adherence to solitude and silence.

[1]Shortly after his election as Master, Munio promulgated the Rule of the Brothers and Sisters of Penance of the Blessed Dominic (Regula Fratrum et Sororum Ordinis de Paenitentiae Beati Dominici), which provided a rule of life (lasting into the 21st century) for the "penitent" laymen and women who had been leading lives inspired by the friars, long called the Third Order of St. Dominic.

In the opening passages, the Rule lays down these prerequisites: "They must be filled with the utmost jealous, burning zeal, after their own fashion, for the truth of Catholic faith".

Upon the ascension to the Throne of St. Peter, the Franciscan friar, Pope Nicholas IV, took Munio's legislation as a reason to edit the Dominican Rule in its entirety.

Following Munio, his friends and his enemies, from Zamora to the papal court over a twenty-year period, Linehan shows how events in a Castilian monastery could influence high politics in the medieval Church.

The capitulars in attendance declared that Munio's reputation for abstinence was so well-founded that the only infractions were of such a nature that it would have involved morsels "without which life was not worth living".

He had been in Palencia only two years, when, tired and disillusioned, he resigned his office and retired to the international motherhouse of the Order, the Monastery of Santa Sabina in Rome.