戒規
During the Council of Trent he was elected one of the council's three presidents, along with fellow cardinals Reginald Pole and Giovanni Maria Ciocchi del Monte (the future Pope Julius III). He continued to serve in that role throughout the remainder of Paul III's papacy, after which he was replaced to placate the Holy Roman Emperor Charles V (1519–56). He was credited with defending not only orthodoxy and Church discipline, but also the universal claims of the Papacy in spiritual and temporal affairs, and with such vigor that the Emperor was affronted. In 1548 (or 1550) he was granted the supervision of the Vatican Library, with the title of "Protettore della Biblioteca Apostolica".