Timeline: Sedevacantism

Earlier in 2026 the Transalpine Redemptorists had publicly declared support for sedevacantism and declined juridical recognition to Pope Leo XIV. On 25 July bishops described as sedevacantist, reportedly including Pierre Roy, consecrated the community's founder, Fr. Michael Mary (Sim), at its monastery on Papa Stronsay in Orkney. The same day the Diocese of Aberdeen said a canonical process had found him guilty of schism and declared him excommunicated.

By mid-September 2023 Catholic World Report reported that Fr. James Altman, already removed as a pastor in 2021, had declared in a YouTube video that Francis was not really the pope but an antipope. Commentators disputed whether his position was sedevacantist or benevacantist.

Fifteen sisters at the CMRI motherhouse in Spokane had come to accept the authority of the post-conciliar popes, and in June 2007 they left the congregation. They were later received into the Catholic Church and formed the Sisters of Mary, Mother of the Church, in the Diocese of Spokane.

In Detroit, Robert McKenna consecrated Donald Sanborn a bishop without a papal mandate. McKenna had been consecrated by Michel-Louis Guérard des Lauriers. Sanborn, rector of Most Holy Trinity Seminary, is known for advocating sedeprivationism.

At Mount Saint Michael in Spokane, Washington, Bishop Moisés Carmona consecrated Mark Pivarunas, superior general of the sedevacantist CMRI, without a papal mandate. Carmona, who had been consecrated in 1981 by Archbishop Ngô Đình Thục, died about five weeks later.

The first issue of Cahiers de Cassiciacum set out the thesis of the French Dominican Michel-Louis Guérard des Lauriers: the post-conciliar popes hold the papacy only "materially," not "formally." Bishop Donald Sanborn is a present-day advocate of the thesis.