In their zeal to "protect God's children" many Church administrators are wrongly blocking the right of the visiting priest to say Mass.
The canonical norm for a priest while travelling is to obtain within the year a "celebret" from his Ordinary which he may present at any church in the world and is to be allowed to say Mass. Since the Dallas Charter most dioceses in the United States have adopted the policy of rejecting that canonical norm and imposing practically impossible bureaucratic regulations (a case by case letter of good standing with the place, date and time of the mass(es) to be said), all but shutting the door to the basic priestly piety of saying mass in church while travelling away from his parish.
Canon law actually says that even if the priest does not have the "celebret" he is to be allowed to say Mass provided his good standing may be presumed.
Can. 903 A priest is to be permitted to celebrate the Eucharist, even if he is not known to the rector of the church, provided either that he presents commendatory letters, not more than a year old (viz. "celebret"), from his own Ordinary or Superior, or that it can be prudently judged that he is not debarred from celebrating.
In other words, innocence is presumed. This law is to be interpreted broadly. Let them say Mass; do not try to unnecessarily stop them, for the good of the Church and of the priests themselves.
Could it be that some in the hierarchy are using the priestly sexual abuse of children as an excuse to promote their own anti-clerical agenda (i.e. against the basic distinctive rights and identity of the priest).
What is often happening in parishes is that visiting priests are simply sheepishly hidden among the laity in the pews because the way to the altar is wrongly barred to them. This has nothing to do with "protecting God's children" but with laicizing the clergy! While the lay people are doing the clerical roles (i.e. being clericalized in those same parishes).
The canonical logic requiring the rectors of churches to allow every legitimate priest to say Mass is related to two other canons: the one urging priests to say Mass daily, even if it must be done alone (it is "earnestly recommended" can. 904); and the other requiring that Mass be said in a sacred place and on a dedicated or blessed altar, except in a particular case of necessity (can. 932). That priests (in good standing) might fulfill this solemn and sacred priestly duty of saying daily Mass (for their own salvation and that of the world) they have the right to do it properly in church, wherever they are, without unnecessary legalistic (pharisaic and non-canonical) obstacles. He's not asking to baby sit. He's just asking to say Mass, i.e. to pray in his distinctive capacity of priest!
This need to say Mass daily in church is not clericalism, it is basic priestly piety. The altars of our churches are not private property but they belong to the entire Catholic body and should be open to all, including, especially, our beloved priests. To oppose this fundamental priestly duty in any way is to oppose Christ in His sacred ministers, a subtle but very real form of anti-clericalism within the ranks of the Church hierarchy and administration which needs to be corrected.
We need to get this straight before we can even consider the same right to say the Extraordinary Form as set out in the motu proprio Summorum Pontificum below.
Art. 2. In Masses celebrated without the people, each Catholic priest of the Latin rite, whether secular or regular, may use the Roman Missal published by Bl. Pope John XXIII in 1962, or the Roman Missal promulgated by Pope Paul VI in 1970, and may do so on any day with the exception of the Easter Triduum. For such celebrations, with either one Missal or the other, the priest has no need for permission from the Apostolic See or from his Ordinary.
Art. 4. Celebrations of Mass as mentioned above in art. 2 may - observing all the norms of law - also be attended by faithful who, of their own free will, ask to be admitted.
Art. 5. § 3 For faithful and priests who request it, the pastor should also allow celebrations in this extraordinary form for special circumstances such as marriages, funerals or occasional celebrations, e.g. pilgrimages.
N.B. All of these directives are to be interpreted liberally, give the people and the priests what they legitimately want, even if it is traditional!