[piusv]

Or that the authority promulgating such heresy would not be legitimate given the Holy Spirit protects the Church from teaching error.

[BlatherNaut]

Where is it written that Popes (who have supreme and complete power and jurisdiction to decide questions of faith and morals and to arrange the discipline of the universal Church) may not convene general councils for practical ("pastoral") purposes?

When the supreme authority (the Pope) communicates his intention that only certain council teachings be considered infallible (“In view of the conciliar practice and the pastoral purpose of the present Council, this sacred Synod defines matters of faith or morals as binding on the Church only when the Synod itself openly declares so.”) how is that not the final word on the subject?