Dear Ladislaus and Angelus,
Would conditional ordination with true Holy oil be the only remedy for the positive doubt? Would Extreme Unction be valid by any priest if the "Holy oil" administered was not truly consecrated? Would Confirmation by any SSPX bishop be valid if the "Holy oil" used was just olive oil with balsam and no consecration?
That Trojan Horse surely seems to have more than one purpose! Regarding recent and upcoming SSPX ordinations; how would we, the faithful, the ordinands, and the priests know where the Holy Oils originated?
Yes, conditional Ordination of the priest in the traditional Rite of Priestly Ordination by a traditional Rite bishop, using properly blessed Oil of Chrism, would seem to be the appropriate remedy to remove the any possibility of Sacrilege, as well as removing any positive doubt about validity of the Eucharist confected by such priests.
So, there are two separate issues here:
1) Sacrilege committed when a priest uses hands or vessels not consecrated with true Chrism. I don't think there is any doubt about this. If the Oil of Chrism used on the priest during his ordination was not real Chrism, then when that priest confects the Eucharist and handles it with unconsecrated hands, a sacrilege is committed. We should avoid going to such priests (outside of emergency) because we don't want to promote the sacrilege.
2) The lacking of the power to Confect the Eucharist because of the use of fake Chrism. This is a more complicated discussion. St. Thomas definitely believed that "the power" to confect the Eucharist was different from "the grace" of Ordination of the priest. You can see this in his discussion
here, which I quoted in a previous post. Following St. Thomas, it would seem that if a priest was consecrated using fake Chrism, he would not even receive "the power" (what St. Thomas calls "the character" of the Sacrament). If that were the case, then there would be positive doubt about the "validity" of the Sacrament of the Eucharist.
The Sacrament of Confirmation would not be valid if the bishop used plain olive oil and balsam. The Oil of Chrism requires consecration with a special traditional blessing prayer said by a traditionally-consecrated bishop. Here is what St. Thomas says,
Whether chrism is a fitting matter for this sacrament?https://aquinas.cc/la/en/~ST.III.Q72.A2Whether it is essential to this sacrament that the chrism which is its matter be previously consecrated by a bishop?https://aquinas.cc/la/en/~ST.III.Q72.A3The answer to both questions, according to St. Thomas, is YES!