If the chair is actually vacant, but physically occupied by a heretic, then the cardinals have the jurisdiction to declare that the former pope vacated the chair by his defection into heresy. If the chair is occupied by a validly reigning pope, the pope possesses full jurisdiction over the cardinals, who have no power to issue and declaration against the reigning pontiff.

There is a clear and specific teaching enshrined in Canon Law regarding "whatsoever offices" (quælibet officia). The term "whatsoever" includes within its scope the papacy, because the papacy is an office. There is disagreement as to how the removal is to be executed; but the text is absolutely clear: All offices are lost ipso jure and without any declaration (sine ulla declaratione) automatically (ipso facto) by the fact alone of public defection from the Catholic faith. Defection from the faith by definition consists in an act of apostasy or formal heresy.

Nevertheless, because it is an office, the officeholder would lose the pontifical office by the fact of defection. This provision applies to all offices whatsoever (quælibet officia), and therefore equally applies to the papacy as it does to every other office whatsoever.

It is not merely "my opinion" that the term "quælibet officia" includes the papacy. The literal meaning of the word "quælibet" by definition is absolutely all-inclusive. Either Meg is in error, or the infallible universal disciplinary ordinance of the Roman Pontiff is in error.

Canon Law doesn't apply to the Pope, period ... unless it's also a matter of divine law, but in that case, it's the divine law which applies to the pope and not the canonical expression thereof.

Destroys my entire argument? What NONSENSE. The canons are not identical, and I never said they were, as you so mendaciously claim. Walters. You don't even understand what you are reading. Both cann. 188.4° and 194 prescribe an IPSO JURE loss of office for public defection from the faith. By its very nature, an ipso jure effect takes place by operation of the law itself, and per se, does not depend on any declaration. Therefore, the commentary of Navarra which I quoted earlier states explicitly, "In the second and third cases, the act of the ecclesiastical authority is declarative, and is necessary, not to provoke the vacating of the right to the office, but so that the removal can be legally demanded ... and consequently the conferral of the office to a new officeholder can be carried out (C. 154)." The provisions forTacit Renunciation and Removal are not identical in every respect, but both provisions are founded on the same doctrine, to wit, that a public act of defection from the faith by heresy or apostasy suapte natura separates the defector from membership in the Church, and thereby directly causes the ipso facto loss of office, as I amply explained earlier, with supporting quotations from St.Thomas, St.Robert Bellarmine, Ballerini, Gregory XVI, and Session 37 of the Council of Constance. Ballerini explains theologically the reason why it is that such an act of pertinacious heresy is in the nature of an ABDICATION. Pope Gregory XVI cites the verbatim passage of Ballerini, who quoted the ruling of Constance, and comments that the defector falls from the pontificate "by himself". Both Session 37 of Constance and Canon 194 explain this kind of loss of office as taking place IPSO JURE. Canon 194 prescribes a merely declaratory sentence in order to ENFORCE the loss of office, which the canon prescribes IPSO JURE. Therefore, the declaration is indeed absolutely necessary, but only to ENFORCE the loss of office that has taken place BY THE ACTION OF THE LAW ITSELF, i.e., ipso jure.

The point is, without the declaration, there is no loss of office.  The declaration is the enforcement; without enforcement, there is no punishment for the crime.  
.
You can argue that a person is guilty of heresy by way of “public opinion” but that has no force of law.  Without a declaration, just like without a judge/jury, a murderer doesnt go to jail...even if everyone knows he did it.

No, I disagree.  This dispute is based on not making the appropriate distinction.  Office itself (i.e. the right to hold it) is removed by the (divine) law itself ... since Popes are not subject to ecclesiastical law ... but the office needs to be stripped materially from the occupant by a declaration.  This is perfectly in line with the material-formal distinction.

No declaration can actually EFFECT the loss of papal office ... not formally.  Papal office is lost formally by virtue of the defection from faith, but lost materially by force of the declaration.  Once again, +Guerard des Lauriers' distinction has it all make sense.