The only problem with all this is that Bishop D’Arcy does not have any direct control over ND. He can suggest, he can refuse to attend, which he has in the past, but he can’t make them stop. ND is run by the Holy Cross Order.
At the same time, it woiuld be a powerful force putting other powerful forces in motion, resulting in a crisis that could well blindside the secular faction. And what we need more than anything else, is a salutary crisis. Business as usual will kill us. Kill us. Here and hereafter.
Meanwhile, would the word "interdict" enable the forces of secular hegemony turn our good Bishop D'Arcy into a Torquemada in the eyes of the Secular Press? Well, they would do that no matter what D'Arcy did, especially if it were effective. Let me repeat that idea: anything he does will turn him into "Torquemada," to exactly the degree that he is effective. We can't be checkmated by that.
But ---- really ---would the secular hegemons give flying figs whether Masses were moved off-campus? What I have in mind is that the honoring of Moloch-Obama ---and the open defiance of the USCCB in one of its (few) really worthwhile rulings --- is already desecrating Notre Dame, and interdict would recognize that fact.
Just the threat of it would be a powerful tocsin to arouse the faithful. It's a bishop's way of saying: this is serious as hell.
And the secular folk --- what could they object to, credibly? They're not worried about where they're goingto Mass! It's not like D'Arcy were messing with something sacred to them...