Does the SSPX have there own annulment tribunal? Sounds like a a la carte authority menu.
This was never as big a deal for me as it was for some outside the SSPX.
On the one hand, they're not issuing declarations of nullity. They're just responding to the issues their faithful present before them, which require pastoral direction, as best they can (e.g., by appointing certain priests to look these matters over, and give their best judgment/opinion on how the Church would rule in normal/sane times).
In reality, this "canonical commission" isn't doing anything that sedevacantist, Resistance, or independent priests don't do on a regular basis.
Consider this example:
A new parishioner (at SSPX, Resistance, sedevacantist, or independent chapel) comes to the priest and says, "Father, I received an annulment from my former Novus Ordo parish, but I would like to now marry Mrs. X. Am I free to do so?"
The priest (of whatever group) has a duty
ex officio et in caritate to advise the soul one way or the other, and not just for the good of the soul, but for his own (for he will either deny this soul marriage unjustly, or he will commit a sacrilege by witnessing an invalid marriage).
It doesn't help that the Society calls this group of advisory priests a "canonical commission," which cannotes to some the usurpation of ordinary jurisdiction (insofar as it may conclude by rendering an opinion which "overturns" -or contradicts- a decision of the competent diocesan tribunal), but this is just window dressing, and not signatory of any claim to jurisdiction.
But render a decision it must, or both faithful and priest become paralyzed (with the only unacceptable "solution" being to submit oneself back to the unreliable decisions of the Novus Ordo tribunals one was trying to escape from).
Once one understands that jurisdiction is for souls, and not souls for jurisdiction (with necessity dispensing from the law, in such measure as is necessary to extricate the soul from grave spiriual necessity), then the advisory opinions of the "canonical commission" make sense.