Sedeprivationism
Sedeprivationism is a doctrinal position within traditionalist Catholicism invented by the excommunicated Catholic theologian Michel-Louis Guérard des Lauriers which holds that the current occupant of the Holy See is a duly-elected pope, but lacks the authority and ability to teach or to govern unless he recants the changes brought by the Second Vatican Council. The doctrine asserts that since this council, occupants of the See of Peter are popes materialiter sed non formaliter, that is "materially but not formally".