ewtn.com/library/Liturgy/zlitur23.htm
ROME, 2 MARCH 2004 (ZENIT).
Answered by Father Edward McNamara, professor of liturgy at the Regina Apostolorum Pontifical Athenaeum.
Q: What responsibility do parishioners have to attend Mass on Sundays instead of going to a lay presiders service when four Masses are available on weekends within a 10-minute car drive? — D.L., Yarmouth, Nova Scotia
A: This theme is treated in Canons 1247 and 1248 in the Code of Canon Law.
Canon 1247 states the obligation to assist at Mass on Sundays while No. 1248 Subsection 2 says that if assistance at Mass is impossible due to the lack of a minister, or for some other grave cause then it is recommended that the faithful assist at the Liturgy of the Word if this is celebrated in the parish church.
The sense of canon law is clear. Assistance at Mass is obligatory, except for a “grave cause.” The use of the expression “grave cause” indicates that the obligation is a very serious one. For obligations that admit more readily to exceptions, canon law usually uses expressions such as “a just cause.”
It is also important to point out that the Catholic’s obligation is to assist at Mass, not to “go to church.” According to the canonical and moral principle “ad impossibilia nemo tenetur” (nobody is obliged to do the impossible), when an objective impossibility exists then the consequent obligation disappears. However, the Church recommends, but does not oblige, that Catholics sanctify Sunday in some other way, such as assisting at a Communion service, following a televised Mass, or praying at home.
Thus, when a parish offers a Communion service when Mass is impossible, this is done in order to allow Catholics to follow the Church’s recommendation to sanctify Sunday in some other way. But it does not substitute the Sunday obligation, which in fact no longer exists.
An objective impossibility need not always be a dramatic situation. Examples of objective impossibility could be age, illness, the need to care for a sick relation, or seasonal variations which make leaving home a hazardous task. Catholics involved in necessary Sunday occupations such as police, medical personnel and flight attendants are also exempt while on duty.
It is not always easy to judge what is objective, as conditions vary from person to person. However, Catholics should not be too light in assessing their difficulties and should be willing to make reasonable sacrifices in order to assist at Mass.
So, if a Catholic can easily assist at Mass in another parish without any great inconvenience, then in conscience he or she is obliged to do so.
Bishops and pastors also have to consider these factors. When Mass is easily available at nearby parishes, sometimes it might be best to have no Communion service at all at the local parish rather than risk disorienting the faithful as to the central importance of Sunday Mass.
A grave inconvenience of such a solution is that it could deprive those least able to find alternative arrangements such as the poor, the sick and the elderly of the comfort of at least receiving Communion.
This grave inconvenience could, however, become an opportunity to exercise and develop charity on the parish level in inviting the faithful to voluntarily share in transporting to Mass those in need.
Should this not be possible, and a significant number of people would be deprived of Communion, then it is probably best to hold the Communion service. But the faithful should be informed that this service is provided for those who have no alternatives and that those who are able should assist at the nearest Mass.
Of course, a Catholic who has even an inkling of the full meaning of the Mass would never voluntarily settle for a Communion service.
