I would have believed that a Catholic Priest, whether Latin or Byzantine, can perform services anywhere in the Catholic realm?
A Catholic priest may be the celebrant of the Eucharistic liturgy in his own Church sui iuris
, and may con
celebrate the liturgy of any Catholic Church sui iuris
(of any ritual tradition). Note the distinction between concelebrating and being the celebrant.
A priest of whatever Church sui iuris
should always be vested in the vestments proper to his Church's ritual tradition regardless of which Liturgy he is (con)celebrating. Thus, a Latin priest may con
celebrate the Divine Liturgy in e.g., a Ukrainian Greek Catholic parish, but while doing so he must wear vestments of the Latin Tradition (presumably, he'd bring his own vestments!). Only a priest with "bi-ritual" faculties (granted by the bishop of the eparchy and Church sui iuris
in which he would exercise such a privilege) can wear, e.g., Byzantine vestments when (con)celebrating a Byzantine liturgy. And in the case of "bi-ritual" faculties, a priest having those faculties may be the celebrant of the liturgy of that other ritual Church sui iuris
. (Hey, them's just the rules, I didn't write 'em, I'm just reporting them.)
Sure, a married Byzantine Catholic Priest may not perform a Latin Rite Mass; How about an unmarried Byzantine Rite Priest?
Married or unmarried, the rules are as above. Any Catholic priest in good standing of any Church sui iuris
may concelebrate the Liturgy of any other Church sui iuris
, but may be the celebrant only in a parish of his own Church sui iuris
unless he receives "bi-ritual" faculties.
(Now then, if a Ruthenian priest wanted to celebrate on his own in a Ukrainian parish, since they are not the same Church sui iuris
, I suspect he'd have to have permission of the local Ukrainian bishop, but as for having to get "bi-ritual" faculties, I guess the permission is the equivalent to that even though those Churches really are both using the same (so-called "Ruthenian") rite.)