A priest of the Greek rite asks to say Mass in my church. In place of a "Celebret" from the Latin bishop in whose diocese he states that he resides, he shows me a letter from a religious superior with the seal of his monastery. Am I justified in accepting this letter, though I have no reason to doubt the character of the bearer as a priest in good standing?
A stranger who desires to say Mass in a church is expected to bear with him as credentials a letter identifying him as in good standing, either from his Ordinary or, in case of a religious, from the superior of his Order or Province. In the case of Orientals the letter is to be from the S. Congregation for Oriental Rites, or the representative of that Congregation in the particular locality. An unquestionably authentic letter from a known bishop would be equivalent to a personal introduction, and that would hold also for a letter from a superior known to the pastor. Other documents have no immediate value as a "Celebret". A pastor is free, however, to allow the hospitality of his sanctuary, once or twice, to a stranger who wears the garb and manner of a priest, without allowing any perquisite [a benefit which one enjoys or is entitled to on account of one's job or position], and with the condition that the stranger leave his name and regular address with the pastor as a guarantee of good faith. A priest who is practically known to his host enjoys the same right to confidence which the host himself might expect. The diocesan statutes may however insist upon the observance of additional conditions and formalities.