With traditional marriage numbers generally speaking at all-time lows, and the aggressive anti-Catholic agenda coming from the mainstream establishment church (which has influenced the state) for the past 50 years or so, I have thought about this question: Could Traditional Catholic weddings be forced to be performed in the catacombs?
I wouldn't doubt that such actions (which I could be involved) might have to happen more frequently in the future; I'm sure they've been done immediately after Vatican II when the Tridentine Mass was abandoned. I'm not talking about the illicit and non-sacramental marriage ceremonies where a priest will go to a hotel room and perform an interfaith ceremony, nor about the ceremonies that the Church of Nice performs.
I am referring to Traditional Catholics without impediments who accept 100% of the Church teachings who for one reason or another cannot marry inside the church building. The most often cause would be that the Nuptial Mass cannot be performs where you go to Mass. If you attend Mass at a monastery chapel or at a Mass center in rented space, Canon Law does not guarantee your right to the other sacraments there, even if you're a regular attendee.
Something like this might happen if you attend Mass said by an SSPX priest in rented space. The rented commercial office space is not a church building, but a catacomb where Mass is said because there are no other options available. If that room only seats 100 people and you want to invite 200, then renting a function hall or outdoor setting would be no problem to an non-parochial priest because they don't have a consecrated church.
One major overlooked issue, but very important, is the Pre-Cana program. Canon 1063 Sec. 2 of the 1983 Code of Canon Law states priests are responsible for "personal preparation for entering marriage so that through such preparation the parties may be predisposed toward the holiness and duties of their new state." Notice the word personal. This means the priest with the engaged couple one-on-one, not group instruction. So even when a diocesan priest (who says the TLM) sends the couple to a "class" or "seminar" for marriage preparation, this is a direct violation of Canon Law, even if the class were orthodox!
Since most diocesan marriage prep programs are heretical, it is safe to stay away from them. If you are being cohered into attending such program, and heresy is taught, then I hope you know better. You should let the priest know, and if he himself doesn't agree with the Church teachings on marriage, then I would not have him officiate. You could always appeal to the bishop, but if he is not orthodox, then forget about appealing to Rome these days.
Another issue for many people is financing the wedding. Keeping in mind that Canon Law does not allow your parish send you an invoice for essential sacramental services (including funerals) and cannot force you to pay a stole fee (especially if you can't afford it). But many Novus Ordo parishes do this anyway. For example, in the Diocese of Worcester, there is now a mandatory fee of $5,000 to have a church wedding, which only includes the service. It excludes the musicians, organists, marriage prep, etc. If somebody can't afford this, then you can't marry in a church building in this diocese.
Finally, if you have to set up a portable altar and have a Nuptial Mass in an irregular location, so be it. As long as the priest is validly ordained and is orthodox, then will validly contract the sacrament.