The Vatican’s disciplinary body, the Dicastery of the Doctrine of the Faith, issued a formal decree, made public by Viganò on Thursday, assigning the senior cleric to a penal canon trial. The charges: the “crime of schism” and “denial of the legitimacy of Pope Francis.”

Such trials are exceedingly rare, and the move underscores a recent effort by the Vatican to take more formal action against a gaggle of archconservatives who have sought to undermine Francis’s papacy from the inside. Conviction could lead to Viganò’s defrocking and excommunication, ending the long career of the 83-year-old Italian cleric who has emerged as the leading symbol of a traditionalist resistance to a papacy perceived by him as wildly liberal.

Viganò, a diminutive firebrand who delivers stinging missives on X and the conservative U.S. outlet LifeSiteNews, said in a statement that he saw the “accusations against me as an honor.” In his comments, Viganò — who has vowed to create a seminary free of Vatican interference — referred to Francis as he always does, eschewing his official title and using his name before he was pope: Jorge Mario Bergoglio.

“It is no coincidence that the accusation against me concerns the questioning of the legitimacy of Jorge Mario Bergoglio and … the ideological, theological, moral, and liturgical cancer of which the Bergoglian “synodal church” is the necessary metastasis,” Viganò wrote.