The Holy Father – Pope Benedict XVI now gloriously reigning – released a Motu Proprio (in Latin) by which he empowers the Cardinal Electors to move forward the day of the beginning of the conclave.
The canonist Ed Peters has looked at the Motu Proprio Normas nunnullas. My emphases:
In the wake of Benedict XVI’s startling resignation, a problem arose: the 17-day delay between the announcement and effective date of the resignation, followed by a minimum 15-day delay before the conclave could legally begin (per UDG 37), meant that the Church was to be, de facto, leaderless for over a month, with basically nothing to do but fret about being leaderless for over a month. As a way around this problem, some speculated (not unreasonably, but wrongly) that the cardinals charged with running skeleton operations during the sede vacante could, on their own authority, advance the start date of the conclave. This apparently simple idea, however, raised some very serious canonical and indeed ecclesiological issues.
Benedict’s motu proprio Normas nonnullas (22 feb 2012) solves the problem, as follows:
37 [Revised]. Praecipimus praeterea ut, ex quo Apostolica Sedes legitime vacat, antequam Conclave incohetur, mora sit interponenda quindecim solidorum dierum, facta tamen Cardinalium Collegio potestate Conclavis initium anticipandi, si constat omnes Cardinales electores adesse, vel etiam proferendi per aliquot dies, si graves obstant causae; tamen viginti diebus ad summum elapsis ab initio Sedis vacantis, cuncti Cardinales electores praesentes ad electionis negotium procedant.
Derogating from UDG 37, the pope has authorized an earlier start of the conclave if all the electors are present. Such a decision now falls squarely within the pontifical provisions for a conclave, and one may leave the choice of a start-date to the competent authority without further concern for the legality of the assembly. [Therefore, it is more likely that there could be a new Pope before Easter and - importantly - there is no question now that the Conclave could have any stain of illegality were the date to be moved up. The question is resolved.]
Time-permitting, I have a few more thoughts later.
Another aspect of Benedict’s motu proprio catches my eye, namely, its reiteration that no otherwise-eligible elector can, for any reason, be barred from participation in the conclave. Over the weekend I saw several chattering heads speculating about Cdl. Mahony arriving in Rome only to be politely shown the door. [They wouldn't do that.] Nonsense. Mahony’s right to admittance is indisputable. As the pope will not disbar an eligible elector at this late date, only Mahony can resolve the complications that his participation in the conclave occasion. [Card. O'Brien of Scotland has voluntarily chosen not to participate because of allegations.]
Recap: As of this moment, there are 118 eligible electors. By Thursday, 8 pm Rome time, there will be 117. One of them, Darmaatmadja, has declared that he will not participate because of physical infirmity (as such, he would be allowed to change his mind and be admitted even if the conclave had started); another, O’Brien, has declared he will not participate for reasons unstated but apparent to all (as such, he would not be allowed to change his mind and be admitted once the conclave has started).