Cardinal Cupich has published a defence of Traditionis Custodes in the Jesuit magazine America. (An earlier article, on Pray Tell, finds a response from Matthew Hazell on Rorate Caeli here.) In this article he argues... well it is actually quite unclear what he is arguing.
Is he suggesting the TC was a response to the failure of the SSPX to submit to the Holy See after Summorum Pontificum? In which case why are their privileges to give absolution and witness marriages in the old Rite not the target of the Holy See's restrictions, instead of the corresponding rights now denied to priests in good standing in the diocese of Rome?
Is he suggesting, instead, that the problem has been that people have been "promoting" the "antecedent liturgies"? But isn't that exactly what Pope Benedict XVI called for when saying that "it behooves us to ...to give them their proper place"?
Or is he arguing something quite different: that the very existence of an alternative form of the liturgy is a wound in the unity of the Church? In which case his complaint is less against the SSPX, or the Faithful who attend the Usus Antiquior under the bishops, but with Pope Benedict himself.
I have published a response in Catholic World Report. (America declined to let me respond.)
Cardinal Cupich begins the story with Archbishop Marcel Lefebvre, in “the early 1970s”. It is worth noting that by the time the SSPX became headline news, with its canonical suppression in 1975 and unauthorised ordinations in 1976, lay groups had been campaigning for the ancient Mass for more than a decade, and had achieved a symbolic, if limited, concession in Pope Paul VI’s Indult for England and Wales which was signed in November 1971, exactly fifty years ago. It was, similarly, the desire of the Faithful, not of SSPX clergy, which was recognised by Pope John Paul II’s world-wide indult of 1984, which does not mention the SSPX, and these Faithful who are again noted as a motivation for Pope Benedict’s Apostolic Letter Summorum Pontificum.
This is worth emphasizing because, although they share an attachment to the former Missal, the International Una Voce Federation (founded in 1965) and its member associations around the world, and the SSPX, are clearly distinct phenomena, and have suffered quite different fates in recent years. In 2016 Pope Francis gave priests of the SSPX special faculties to hear confessions, and in 2017 he made provision for them to officiate at marriage services. They still enjoy these privileges today. Priests serving the faithful within the structures of the Church, on the other hand, have just been forbidden to do either thing using the older books used by the SSPX in the very diocese of Rome. If Traditionis Custodes is motivated by disappointed hopes for “healing and unity” with the SSPX, it seems to have sadly mistaken its target.