I believe this is wrong. You don't need legal loopholes to prove that the recent decree from Rome is invalid and unjust. ergo - no excommunication took place. Despite the SSPX trying to place themselves into the false conciliar church, they are not officially "in" and as oil and water never mix, they have not signed any agreement officially nor placed their properties or members under the control of Rome. I say not officially though they are trying in many cases, like shaking the bottle of salad dressing and it sometimes has the appearance of being mixed, but when it settles out, the oil again separates from the water.
The simple argument is the one that the Archbishop understood decades ago, which unfortunately, the SSPX won't publish now because they are cow towing to Rome, yet the argument still applies. The conciliar church is the schismatic party and if they declare that you are out of communion with them, it means the excluded party *may* still be Catholic at least. The excluded party (SSPX), so long as it uses bishops and priests from a pure line, still dispenses valid sacraments, and remains "in" the church. The supplied jurisdiction comes directly from the papacy in canonical terms which cannot be removed any more than the indelible mark can be removed from a validly ordained priest.
Besides this, there are the legal loopholes that a sweeping excommunication is not valid when no crime has been committed. You have to do something to be excommunicated. You don't wake up one morning and find yourself excommunicated. Furthermore, no one can be excommunicated for trying to be a good Catholic and clinging to the true 7 sacraments or the Mass of all time. Those that are out of communion are those imposters sitting in the chairs of authority in Rome. Besides this, there is the realization that the new synodal church has set up a new government structure similar to Soviet governments. Archbishop Lefebvre called this out before the Vatican II council. The start of it was with Paul VI with the "collegiality of bishops"codified in Lumen Gentium, which was a "a dangerous democratization and collectivism that would erode the traditional hierarchy of the Catholic Church." Within this, for example they have been rubber stamping communist bishops in China. There are too many injustices to count, travesties, heresies, sacrileges, atrocities - such things cannot come out of Christ's true church bearing the 4 marks. They have forfeited their claims to authority because they transgress the higher laws. They insist on this obedience to the pope as if he can do whatever he pleases with no regard for the higher law.
A schismatic party cannot declare the non schismatic party schismatic. One day, this will be cleared and the diabolical disorientation dispersed.
Yes, said the Archbishop, you are right to say that we are not in communion with you. We cannot be in communion with the conciliar false church.
You can't say that the excommunications are valid unless you yourself accept modernist Rome as the true church & churchmen. You contradict yourself. It seems based out of some ill will towards the sspx. If any other traditional catholic group (more hardline) were to ask Rome about their status, they would also be called "schismatic" and unrecognized, having no link of authority or unity to modernist Rome (according to the modern authorities). But of course, they maintain their link to "Eternal Rome", preserving the valid lines through the crisis.
In short, to quote +Williamson "your eminence, we have two religions here" "Two "churches" " Only one can be the true church, and the other has forfeited its rights and claims. The vatican has been infiltrated since the 1950s. Fortunately, the vatican does not equal the church, and Christ is the primary head of the church first over the pope.
Did the Archbishop not see his "excommunication" as being invalid? He died before it was lifted, and certainly, he is not in hell.