In a June 20 post on X, the archbishop published a letter he said he received from the dicastery over email informing him of the trial.

The letter, written on the dicastery's stationary and signed by Msgr. John Kennedy, secretary for the dicastery's section for discipline, said the archbishop was summoned to appear at the dicastery's office June 20 to hear "the accusations and evidence against him regarding the crime of schism of which he is accused."

It continued to detail the specific elements of schism, accusing the archbishop of "public statements which result in a denial of the elements necessary to maintain communion with the Catholic Church: denial of the legitimacy of Pope Francis, rupture of communion with Him, and rejection of the Second Vatican Council."

The Vatican press office did not immediately respond to a request for comment. However, Vatican News, which is also part of the Dicastery for Communications, published an article on the archbishop's post quoting Vatican Secretary of State Cardinal Pietro Parolin from the sidelines of an event at the Pontifical Urbanian University in Rome June 20. He stated that Archbishop Viganò had developed "certain attitudes and gestures which he must respond to" and that he will have the opportunity to defend himself.

Reporting from the same event, the Italian news agency ANSA quoted the cardinal as saying that it is "normal that the (Dicastery for the) Doctrine of the Faith has taken the situation into its own hands and is carrying out the necessary investigations to examine this situation in depth."

"I always appreciated him as a hard worker who was very loyal to the Holy See, in a sense also an example; he worked extremely well when he was an apostolic nuncio. I don't know what happened," he said, according to the ANSA report.

Archbishop Viganò is active on social media and writes often on the blog of his association, "Exsurge Domine," where he has continued to be vocal about his opposition to Pope Francis and Vatican II.

For example, in a 2020 letter written by Archbishop Viganò and published on Inside the Vatican, the archbishop said "it is undeniable that from Vatican II onwards a parallel church was built, superimposed over and diametrically opposed to the true Church of Christ."

Archbishop Viganò also wrote in a post on X in November 2023 that Pope Francis' "incompatibility" with the function of the papacy "confirms his defect of consent in the assumption of the Papacy," but he specified that his comments should not be taken to mean he shares the opinion of sedevacantists.

Reacting to the letter he received from the dicastery about the trial, the archbishop wrote, "I regard the accusations against me as an honor." The accusation against him issued for questioning both the legitimacy of Pope Francis and the Second Vatican Council confirms that the "synodal church" promoted by the pope is the metastasis of the "ideological, theological, moral, and liturgical cancer" of Vatican II, he wrote in a blog post published June 20.

He went on to write that he does not want "any ecclesial communion" with the pope or his collaborators but claimed that he remains "in full communion with the Roman Catholic Apostolic Church" and the magisterium of the popes.

The Code of Canon Law defines schism as "the refusal of submission to the Supreme Pontiff or of communion with the members of the Church subject to him."