Leo called on one of his closest advisors, Sylvestre Mazzolini Prierias, to examine the Theses and determine the errors of Luther. Prierias published an opinion officially accusing Luther of heresy. After a review by three commissions of theologians and four consistories of cardinals, Leo issued the papal bull “Exsurge Domine” (Arise O Lord) which demanded the retraction of forty-one of Luther’s ninety-five theses. When Luther refused to do so, the pope issued the papal bull “Decet Romanum Pontificem” on January 3rd, 1521. Luther was officially excommunicated along with many of his followers. Nonetheless the number of his followers continued to increase.

In an effort to ensure that Scandinavia would not become Lutheran, Leo instructed his nuncio to grant absolution to Christian II of Denmark for various crimes. The pope also rewarded Henry the VIII for his writing against Luther and granted Henry the title of Defender of the Faith.