The public sin of manifest formal heresy causes one to lose office. This is Divine Law. After that, Ecclesiastical Law kicks in and the heretic is excommunicated. Supplied jurisdiction makes the heretic's actions valid but not licit until the Church declares him officially to be a heretic. This I believe is the substance of Fr. Chazal's argument.
https://cdn.restorethe54.com/media/pdf/1917-code-of-canon-law-english.pdfYes, the public sin of heresy causes an automatic "vacancy" (Canon 188.4). But the person "loses the office" in stages, according to the Church (Canons 2314 and 2257-67). First, by the fact [
ipso facto], he loses the power to exercise his office. Next, after he is "declared" a heretic, he loses the fruits of the office. And after he is "condemned," he loses the office
per se, ontologically. It is the somewhat academic debate over those stages of excommunication that is confusing everyone.
The first stage "
ipso facto excommunication for heresy" is enough for the faithful Catholic to know he must avoid "submission" and "communion" with the heretic former officeholder.
The "
ipso facto vacancy" and "the
ipso facto excommunication" are not, as you suggest, two separate events. Rather, the "public defection from the faith" (Canon 188.4) that causes the office to "become vacant upon the fact [
ipso facto]" is the same event that causes "all apostates from the Christian faith and each and every heretic or schismatic" to "incur by that fact [
ipso facto] excommunication" (Canon 2314). In other words, the removal the cleric from office and the personal excommunication are two
different effects of the
same cause, the same event: the manifestation of "
ipso facto heresy."
For practical purposes, we can stop the analysis there. The unrepentant, public
ipso facto heretic
cannot legally act in any official capacity in the Church. His actions are "impounded" until he repents. So his actions and dictates
have no force for any Catholic. Not only do we not have to follow his dictates while he is in the state of illegitimacy, but we have the moral obligation to avoid "communication" with that heretic, as Canon 2316 states:
Whoever in any manner willingly and knowingly helps in the promulgation of heresy, or who
communicates in things divine with heretics against the prescription of Canon 1258, is suspected of
heresy.
It is not enough that we just say we disagree with the heretic on his heretical teachings. No, we must not give the impression that we are in any way "in communion" with that heretic. Otherwise, we are "consenting" to his heresies. This is what the SSPX does when they say that they are "in communion" with a heretic Pope. Their position flies in the face of Canon Law.