Q. 1. Can a priest celebrate Holy Mass anywhere or does it always have to be in a Catholic Church?
A. 1. That is a good question. As a general rule, if Holy Mass can only be celebrated in a church, then it should be celebrated in a Catholic Church! Canon Law # 932 §1 states: "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."
Since the Canon Law refers to a "sacred place," it become necessary to understand the meaning of those two words. Usually, a "sacred place" is a reference to a church building. At the same time, it may refer to chapels (referred to as oratories in the Code of Canon Law) found in convents, in the hospital, in some airports, at Catholic Universities and Colleges, etc... Whatever the location, the chapel had to be approved by the diocesan Bishosp in accordance with Canon Laws # 1223 & 1229.
Can. 1223 "By the term oratory is understood a place for divine worship designated by permission of the ordinary for the benefit of some community or group of the faithful who gather in it and to which other members of the faithful can also come with the consent of the competent superior."
Can. 1229 "It is fitting for oratories and private chapels to be blessed according to the rite prescribed in the liturgical books. They must, however, be reserved for divine worship alone and free from all domestic uses."
I am sure that many of you have heard of a priest going to celebrate the Holy Mass in a home for a very sick or elderly person who cannot attend the Church because of medical reasons. In such cases, a table is set up with the basic necessities as outlined by the Catholic Church. During such Masses, only the sick person can receive the Holy Eucharist. If the caregiver cannot attend Holy Mass at a local Church and it is a day of obligation, than the caregiver can also receive Holy Communion.
Military Chaplains have been known to celebrate Holy Mass in the open air, in tents, on land and at sea, all depending on the situation. Missionaries in remote areas where there are no Churches may also be required to celebrate the Mass in open air or in a tent.
Then you have the situation of when a priest is travelling or on holidays. If he is on a one week fishing trip in a remote area where there are no Churches, he will be required to celebrate his daily Mass in his cabin, tent or hotel.
All of the above examples meet the condition of Canon Law # 932 §1 where it states "necessity requires otherwise."
What about celebrating Holy Mass in a non-Catholic Church? As a general rule, it should not be done because it may create confusion among the faithful, some believing that all Churches are equal, when they are not. But in exceptional cases, for a very short period of time, in instances where the Catholic Church was destroyed by earthquakes, tornadoes, hurricanes, the Bishop may approve of the celebration of the Holy Eucharist in a non-Catholic Church in accordance with Canon Law # 933 wehere it states: "For a just cause and with the express permission of the local ordinary, a priest is permitted to celebrate the Eucharist in the place of worship of some Church or ecclesial community which does not have full communion with the Catholic Church so long as there is no scandal."
The question to ask here is, "Is it not better to attend Holy Mass in a non-Catholic Church on a temporarily basis versus not being able to attend Holy Mass at all?"