Tridentine has never been abrogated.
Stickler has consistently defended the position that the Tridentine Mass was never forbidden or suppressed. He believes that the Novus Ordo Mass contradicts the true wishes of the Second Vatican Council, and once told the Latin Mass Society of England and Wales that its movement “has full legitimacy in the Church.”
In 1986, Pope John Paul II appointed nine cardinals (Stickler, Ratzinger, Mayer, Oddi, Casaroli, Gantin, Innocenti, Palazzini, and Tomko) to study the legal status of the Tridentine Mass, specifically whether Pope Paul VI authorized its suppression and whether a priest has the right to freely celebrate this Mass. According to Stickler, all but one of the cardinals decided the Tridentine Mass was not forbidden, yet they unanimously agreed that no priest can be hindered from celebrating this Mass, even despite the orders of his bishop.
Recently, in discussions with Bishop Fellay, Cardinal Hoyos reportedly admitted the legal status of the Tridentine Mass but stated they cannot declare it in public because of the heat they would take from the bishops.
Father Franz Schmidberger of the SSPX related in a February 2001 speech that Cardinal Castrillon Hoyos admitted reluctantly that the Tridentine Mass has never been abrogated. According to Father Schmidberger, Cardinal Hoyos said, “Okay, we recognize that the old Mass is not abrogated and is legitimate, but we cannot say it publicly because there will be too much rebellion and difficulties with the bishops. We cannot say it publicly.”
And that would explain why the reported terms of the new motu proprio include a provision that would allow bishops to expressly forbid offering the Tridentine Mass.