A reader writes:
All of this is true. But it does not imply that the answer is that a pope cannot be fired. The fact that the laws on the books provide no avenue for the removal of a pope doesn’t mean that the laws couldn’t be changed to make it possible.
There is an authority in the Catholic church that possesses power at least equal to that of the pope: the Ecumenical Council. The decrees of an Ecumenical Council have a force like that of Papal dicta, and they constitute the canon law by which the Pope governs. The Councils write the laws. So the Pope is supreme within the law, but the Council is supreme over the law. As a result, a Council can remove a pope. In fact, it’s happened several times.
The Councils of Pisa, Constance, and Basel all fired one pope or another. At the Council of Pisa in 1409, the bishops dethroned the two rival schismatic popes, Benedict XIII and Gregory XII, and elected a third, Alexander V. At the Council of Constance (1414-1418), the Council accepted the resignations of Benedict XIII and Alexander’s successor John XXIII and deposed the third papal claimant, Benedict XIII. Of course, this Council also settled matters by retroactively declaring some of the schismatic popes as “anti-popes,” so they weren’t popes to be deposed in the first place, and repudiating the Council of Pisa as a mere meeting of bishops, and not a Council at all. At Basel, Pope Eugene IV (who has no rival claimant!) was deposed in 1439, but the Council itself was declared illegitimate by the rival Council at Ferrara and Florence. So, on the books, it looks like no popes were fired. But that’s only because the Councils wrote the books.
It is still an open question as to whether Councils are supreme over the pope, and whether a Council can be convoked without papal authority. Right now, the consensus is perhaps in favor of the pope. But these are questions of doctrine and canon law, and questions of doctrine and canon law are ultimately decided by Council. There’s nothing preventing someone, if they can get sufficient support, to convene a Council that declares itself legitimate and then deposes the pope.
There’s an addendum to this. At the height of the Thirty Years War in 1632, the representatives of Spanish (i.e., Hapsburg) interests in Rome accused Pope Urban VIII of insufficiently supporting the Catholic cause in the conflict. Following a famously fractious consistory meeting, allies of the Spanish party privately threatened to convene a Council and remove the pope. Urban, for his part, took the threat seriously.