Ed Peters, who writes “In the Light of the Law,” a blog on the canon law of the Catholic Church, has explained why Cardinal Sean O'Malley's shindig at the U.S.-Mexican border may well have trespassed Church laws governing where Holy Mass may be celebrated: only in sacred spaces, unless necessity, such as Catholics fighting on the battlfield, requires otherwise.

Wrote Peters:

My concern is not political (both sides of the immigration debate make good points and reasonable minds may differ about those), nor is my concern religious per se (we have participated in faith-based events at the border and we made sure our kids experienced them too). Rather, my concern is liturgical and canonical, specifically, treating the venue of holy Mass as an opportunity to make political statements and regarding canon law on liturgy as little more than suggestions.

Canon 932 § 1 (one among the 1,752 canons that Roman Catholic bishops must observe and enforce per c. 392) states that “The eucharistic celebration is to be carried out in a sacred place unless in a particular case necessity requires otherwise; in such a case the celebration must be done in a decent place” (my emphasis). Obviously, no one suggests that the border is a “sacred place” in the canonical meaning of that term, so the question becomes whether necessity required holy Mass to be celebrated at the border.

I think not. [Mass at the border raises liturgical and canonical issues, April 4, 2014 ]

Peters added that a priest should not celebate Mass outside an abortion clinic either. And he is also concerned about the Mass being conscripted to serve political purposes. If it is taken out of a sacred place to hammer on immigration, another bishop or priest might do likewise for his pet cause. Concluded Peters:

But let’s not assume that sacred spaces for worship may be ignored just because a photogenic backdrop for one’s political views (however decent they may be) presents itself, and let’s not distort Church law by claiming that “necessity requires” Mass to be celebrated in these sorts of places. Because neither assertion is true.