Listen to this story:

ROME – Roughly a year after he resigned the papacy in February 2013, Pope emeritus Benedict XVI found it necessary to respond to an Italian journalist’s query about whether that decision was valid, though his irritation seemed evident.

“There is absolutely no doubt regarding the validity of my resignation from the Petrine ministry,” the emeritus pope wrote. “The only condition for the validity of my resignation is the complete freedom of my decision. Speculations regarding its validity are simply absurd.”

Benedict was responding to theories that had circulated in some traditionalist Catholic circles to the effect that he had been forced to step aside, perhaps with threats to expose various Vatican scandals, in order to make way for the more progressive Pope Francis.

Bear in mind, those doubts metastasized despite the fact that Benedict XVI delivered his resignation in person, in real time and in his own voice, and in a moment in which he was clearly in full possession of his faculties. (I mean, for the love of God, he proclaimed the resignation in flawless Latin!)

So, imagine what might happen should a papal resignation be announced by someone else, years later, based on a vaguely worded letter which might or might not actually reflect the pope’s will at the moment it was invoked.

That’s precisely the question posed by a recent interview with Pope Francis by the Spanish newspaper Abc, in which the pontiff revealed that shortly after his election in 2013 he signed a letter of resignation in case of medical incapacity and gave it to his Secretary of State at the time, Italian Cardinal Tarcisio Bertone, who resigned shortly afterwards.

Francis did not indicate whether his letter defined what would constitute “incapacity,” nor who would have the authority to invoke the letter and thus declare a sede vacante, meaning a transition from one pope to another.

As Francis noted in the interview, this is not the first time a pope has written such a preemptive resignation.

We know that in 1804, Pope Pius VII signed a document of renunciation should he be imprisoned in France while in Paris to attend Napoleon’s coronation as Emperor. Pope Pius XII likewise signed a similar document in 1943, in case he were kidnapped by the Nazis; according to the legendary Cardinal Domenico Tardini, Pius XII had indicated that if he were taken away, the College of Cardinals would regroup in Lisbon, Portugal, to elect a successor.

St. Pope Paul VI wrote a letter of resignation in 1965 in case of incapacity and kept it in his desk, making his priest secretary, Pasquale Macchi, aware of its existence. The idea was that Macchi would give the letter to the Dean of the College of Cardinals, who could then pronounce the office vacant.

“In case of infirmity, which is believed to be incurable or is of long duration and which impedes us from sufficiently exercising the functions of our apostolic ministry; or in the case of another serious and prolonged impediment,” Paul VI wrote, he intended to step down “both as bishop of Rome as well as head of the holy Catholic Church.”

St. Pope John Paul II wrote two such letters, in 1989 and 1994, which were revealed as part of the document in his canonization process. In them, the pope provided for his resignation in case of “incurable illness” which makes it impossible “to exercise sufficiently the functions of the apostolic ministry.” John Paul specified that the decision to invoke the letter should be made by a group of cardinals, including the Dean of the College of Cardinals, the heads of dicasteries in the Roman Curia, and the Cardinal Vicar of Rome.

Here’s the problem with all the above.

Papal resignations are governed by canon 332, subsection 2, of the Code of Canon Law, which states: “If it happens that the Roman Pontiff resigns his office, it is required for validity only that the resignation is made freely and properly manifested but not that it is accepted by anyone.”

The key word is “freely.” Even if a pope freely signed a resignation letter ten years earlier, how would we know it was still his will when it was actually invoked?

Church historians often cite Paul VI as a cautionary tale, since he eventually changed his mind about resignation, declaring to his confessor, Italian Jesuit Paolo Dezza, that it would be a “trauma for the church.” In one sign of his change of heart, in September 1977 L’Osservatore Romano carried an article titled “Why the pope can’t resign.”

All that, naturally, would have generated serious doubt about the pope’s intent should Paul’s letter ever have been invoked.

The late Father James Provost, one of America’s most renowned canon lawyers, was dubious about the legal validity of undated resignation letters signed in advance and put into effect by someone else. Shortly before his own death in 2000 he wrote in America, “He [the pope] would have to be of sound mind on the date when the letter is eventually dated for it to be canonically valid.”

That’s just one opinion, but it’s likely to be widely discussed and shared should the scenario ever materialize, potentially creating doubts about the legitimacy of a new papacy before it even begins.

In the case of Francis’s letter, there are other question marks.

For one thing, how serious could Francis actually be if he handed it off to an aide who exited the scene ten years ago, and never bothered to follow up to find out what happened to it? For another, it’s not clear from the way Francis described it who would be empowered to invoke the letter’s provisions.

In the past, it’s been assumed that a decision to declare the Throne of Peter vacant would have to run through at least some subgroup of cardinals, if not the entire College of Cardinals. Shortly after Celestine V stepped down in 1294, his successor, Boniface VIII, issued a decretal affirming the validity of that resignation, offering as proof that Celestine had obtained the “concordant counsel and assent” of his cardinals.

Yet under Francis, given the way he’s opened up Vatican leadership to non-cardinals and even non-clergy, it’s not even intuitively obvious that would be his will.

In other words, it’s just not clear to anyone whether, or how, a pope can resign in advance … which, perhaps, helps explain why none of the previous preemptive resignation letters were ever invoked. After all, recall that Pius VII actually was imprisoned by Napoleon from 1809 to 1814, exactly as the pontiff had foreseen, but no one ever tried to declare a sede vacante based on his 1804 letter.

So what would happen if Pope Francis were to suffer a grave medical condition that rendered him permanently incapable of governing, and someone tried to invoke the 2013 letter left in Bertone’s care?

As unsettling as such uncertainty may be, the only honest answer probably is that God alone really knows.