My former Christian History professor at Yale, The Rev. R. Guy Erwin (ELCA; photo at right), admits that the stunning news of the Pope's resignation makes this week for a church historian like himself "like the Super Bowl, the World Cup, and Wimbledon rolled into one! (But unfortunately, the best parts are not played in the open.)"
He provides some perspective on the resignation news:
The canon law says "renuntiatio" or to "give up" or "resign" in the one sentence that governs this possibility (Can. 332 sec. 2). It says he can do so, and resignation is valid if he does it freely and publicly, and--here's the old theological question--it doesn't have to be recognized by all to be valid. That is, even if some go on believing that he is still pope, in the canon law he is not.
Presumably, on the day the pope has indicated (28 February) the See of Peter becomes vacant just as if he had died, and the College of Cardinals take over their "sede vacante" role until a new Conclave is called and a new pope elected.
It seems crazy to me that the conclave might actually be meeting right up to Holy Week. But all the steps are determined by laws, and once the office is vacant, the church goes on autopilot. But all the rest is terra incognita; there's never been an ex-pope in good standing with the church (the schismatic popes deposed were later declared antipopes).* He will have at least the status of a retired bishop. My guess is that he will want to be thought of as a "simple priest" and go into semi-monastic seclusion within the walls of the Vatican (ongoing legal immunity) and not be seen again in public until his funeral. Seems strange, perhaps, but what else could he do? There's no place in the basilica to seat an ex-pope when the new pope says Mass.
Though I am not a fan, I say this all with some sympathy for him--whatever is on his heart or conscience, he is in a very lonely place, and will have left a really mixed legacy made more complicated by this way of leaving it. And he is far too intelligent a man not to understand all that and be troubled by it. So if resigning is his "I can do no other," then it's for very weighty reasons.
*There is one correction I'd make: I said there had never been an ex-pope in good standing with the church. That's a bit of an exaggeration, but the only one who wasn't either a simonist or a schismatic, (Celestine V, who was, in fact, a saint) was imprisoned by...and possibly killed by his successor, who feared the ex-pope would be a magnet for rivals.