From a reader:
Does one’s obligation to assist at Mass on a Solemnity follow the prescriptions of the diocese where you’re currently located, or do you follow the prescriptions of your home diocese? I will be in Philadelphia on business on Ascension Thursday (where the holyday has NOT been transferred to the following Sunday); however I will be home in ___ by the following Sunday (where the solemnity regrettably has been transferred).
Is it possible in my case that I will be obliged to attend two Ascension Masses? Of course, this question is merely intellectual in that I will not pass up the opportunity to celebrate Ascension on the traditional day.
We need to dig into our General Norms, the first section of the Code of Canon Law that lays out how laws are to be read and understood.
(While we reach for the book, we should say a little prayer that our bishops to come to their senses and restore the calendar to its proper state and give us back Ascension Thursday.)
Canon 12 says that everyone is bound by universal law, but if that universal law is exempted in a particular territory, then everyone “actually present”
in that territory is exempted.
Canon 13 (paragraph 2) shows us that travelers are not bound by the particular law of their territory while they are absent from it (unless the law is a personal one, or the transgression of that law causes harm in their territory – e.g., a bishop decrees that all of his priests offer one Mass for a cleric when he dies. Fr. Smith is out of the country when he hears of the death of Deacon Jones. Even though he is outside of the diocese, Fr. Smith is still obliged to offer Holy Mass for Deacon Jones, because to do otherwise would cause harm to Deacon Jones by depriving him of the grace that is expected).
Travelers are also exempt from the law of the territory in which they are present, except for those laws which pertain to public order, determine the formality of an act, or which regard immovable goods located in the territory.
Lastly, our good friend, canon 18,
“Laws which establish a penalty, restrict the free exercise of rights, or contain an exception from the law are subject to a strict interpretation.”
This the current incarnation of the ancient axiom about the interpretation of the Church’s laws as “odia restringi, et favores convenit ampliari” that is when a law imposes an obligation of some kind, we interpret the law as strictly as possible so that people have the most freedom, and when a law gives something favorable we interpret the law as loosely as possible to make sure that people are able to benefit to the greatest extent (Regula Iuris 15).
So, since the feast of the Ascension has been moved in some places, and not in others, and because it is celebrated by some who use the 1962 Missale Romanum in those places where the feast has been legitimately transferred, we are left to figure out what our obligations are.
If a traveler named “Sempronius”, from a diocese where Ascension Thursday is celebrated on Sunday, is actually present in a place where Ascension Thursday is (shockingly) on Thursday, Sempronius is under no obligation to attend Mass (canon 13, 2.2).
If a traveler named “Exuperantius”, from a diocese where the Ascension has not been moved is actually present on Thursday in a diocese where Our Lord’s earthly sojourn has been liturgically delayed to Sunday, he too is under no obligation to attend Mass (canon 13, 2.1).
If, however, Sempronius goes to Mass on Ascension Thursday whilst traveling, and returns home before Sunday, his obligation to attend Mass on Sunday still applies, even though it will be a repeat of the prayers and readings he’s already prayerfully participated in with full, conscience and active participation. In other words, Sempronius is fortunate enough to celebrate Our Lord’s Ascension twice.
On the other hand poor Exuperantius is deprived of the celebration of Our Lord’s Ascension this year, since he would celebrate the Sixth Thursday of Easter, and then the Seventh Sunday.
By the way, if a parish is celebrating the Ascension on Thursday using the 1962 Missale Romanum, even in a place where the lawful authority has transferred the Feast, those parishioners have no obligation whatsoever to attend a Tridentine Mass on Thursday, nor do they have an obligation to attend a Novus Ordo Mass on Sunday, even though it means they will miss out on the celebration of the Ascension.
That’s the way it goes.
Flavin wrote in The San Francisco Chronicle in 2008 that then-presidential candidate Barack Obama made her heart “flutter, nay, pound”” 
From a reader:
