[ELS]

If that is the 1913 (or thereabouts) CE that is on the New Advent site, that may explain why it doesn't have an explanation of the celebret offered by the Ecclesia Dei Commission.

I don't know the exact details, but a priest can receive a celebret from Ecclesia Dei for saying the TLM and not need the permission of the local ordinary to do so.

[sinkspur]

I'm looking for documentation.

Here's something from the infamous Father Scott of the SSPX, written upon the defection of a Father Vanderputten from the Society:

He himself has obtained a celebret from Cardinal Ratzinger, and now celebrates the Indult Mass, under the condition that he places himself under a diocesan bishop within six months.

Source.

Again, I would find it odd that the Vatican would approve of a "free lance" priest celebrating the Tridentine Mass outside the jurisdiction of a bishop. Every priest has to be attached to a bishop or superior.

[Canticle_of_Deborah]

I don't know the exact details, but a priest can receive a celebret from Ecclesia Dei for saying the TLM and not need the permission of the local ordinary to do so.

That may be the situation. I don't know much about it. It was new to me when my friend told me.