Can. 749 §1 In virtue of his office the Supreme Pontiff is infallible in his teaching when, as chief Shepherd and Teacher of all Christ's faithful, with the duty of strengthening his brethren in the faith, he proclaims by definitive act a doctrine to be held concerning faith or morals.
**§2 **The College of Bishops also possesses infallibility in its teaching when the Bishops, gathered together in an Ecuмenical Council and exercising their magisterium as teachers and judges of faith and morals, definitively declare for the universal Church a doctrine to be held concerning faith or morals; likewise, when the Bishops, dispersed throughout the world but maintaining the bond of union among themselves and with the successor of Peter, together with the same Roman Pontiff authentically teach matters of faith or morals, and are agreed that a particular teaching is definitively to be held.
*§3 No doctrine is understood to be infallibly defined unless this is manifestly demonstrated. *
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#3 above agrees with what V2 explained in its footnotes, it agrees with what Pope Paul VI said in his explanation of the council, it agrees with the MANY theologians who have explained that it is NOT REQUIRED to be held with an "assent of faith", hence it's not infallible.