What is a celebret, and why is it important?

The Code of Canon Law exists for a reason and if priests and bishops would simply follow it, the Church would not have to address many of the problems - large or small - of the present day. As proof of this claim, consider the following story from the Catholic News Agency about Erwin Mena who has been posing as a Catholic priest in California:

He was good at it, too, reportedly. He attended seminary in El Salvador for a time years ago before dropping out, so he was able to convincingly officiate Masses, funerals, and even at least one wedding. He had a likeable personality and said all the right things.  

On Tuesday, he was arrested by Los Angeles police for allegedly impersonating a Roman Catholic priest and on suspicion of grand theft. Mena allegedly conned parishioners into buying thousands of dollars’ worth of fake tickets to see Pope Francis in the fall, and he would sell religious CDs and books only to line his own pockets with the profit. He has been charged with 22 felonies and 8 misdemeanors, according to a criminal complaint filed by the L.A. County district attorney’s office.

For 5 or 6 months beginning in January of last year, Mena, who would also go by Menacastro, showed up at St. Ignatius of Loyola parish in Highland Park, claiming to be a visiting priest covering for the pastor, who was on vacation, according to police reports [more].

Thankfully, such things do not happen on a frequent basis and the Church has a law to ensure they do not happen, a law that clearly was not followed in this case.

As a preventative measure, the universal law of the Church stipulates:

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, from his own Ordinary or Superior, or that it can be prudently judged that he is not debarred from celebrating (canon 903).

This is a canon that every priest should know. Furthermore, no priest should take offense at being requested to show a commendatory letter to someone who does not know him in order to prove his identity because this canon seeks not only to protect his right to offer the Holy Mass (cf. canon 900 § 2), but also the right of the faithful to the valid and licit celebration of the sacraments (cf. canons 213 and 214).

Many dioceses now issue such a letter each year in the form of an identification card. It states that the priest is in good standing and requests that appropriate hospitality be extended to him. A celebret in this fashion might also include a photograph of the priest lest there be any doubt as to the authentic bearer of the card. Such is the case with the celebret I have from the Diocese of Springfield in Illinois, where I have a domicile (cf. canon 102 § 1), and from the Diocese of Rome, where I have a quasi-domicile (cf. canon 102 § 2).

Even if the priest's Diocese does not issue a celebret each year, he can easily request what is commonly called a Letter of Good Standing or a Letter of Suitability from his Bishop or his Vicar General.

Now, if the priest is not known by the rector, can it really be prudently judged that the unknown priest is not debarred from celebrating the Mass without inspecting a commendatory letter? I think not, unless someone known and trusted by the rector can vouch for the unknown priest. Therefore, the pastor of the parish should have required Mena to show such a letter (because he was not known by the diocese or by his parishioners), commonly called a celebret. If he had required the celebret be shown to him, all of this mess could have been avoided from the outset.