Just to derail a bit, that means justification by desire or justification by bƖσσdshɛd does not occur.
Earlier you saidSo is this unbaptised person justified since they go to limbo?
These are questions that it might be worth discussing among those of good will here to believe the Church's dogmatic teaching on EENS, and we should stop wasting our time on trolling heretics like Angelus.
Just as St. Thomas Aquinas fully articulated the distinction between natural punishment / natural happiness, rooted in justice, and supernatural beatitude in the Kingdom, something above human nature, which, being owed to no one and not required for happiness, there would be no injustice in not granting it, since it's a completely free gift ...
similarly, I believe that there's confusion between a natural justification and a supernatural one, where infants in Limbo, for instance, are not in a "state of grace", meaning that they do NOT possess the supernatural virtues of faith, hope, and charity (where of course only charity remains in eternity, as the Holy Ghost teaches through St. Paul).
Since these innocent souls have committed no actual sin, they are not in a state of enmity with God, which is usually what's contrasted with justification, except that what people often mean by justification is ... being in a state of grace, and they're not in that state either. So they're neither justified nor non-justified. They're in a sort of natural friendship with God, where they believe in Him, obey Him, assent to His truths and to the law He has written in their hearts (the natural law) ... in a natural way only, since they do not and cannot have supernatural faith and supernatural charity.
So when Pax says there can be no justification except in the Church, he's assuming the definition where justification means being in a state of grace and having the supernatural virutes, in which sense he's correct. BUT ... that does not mean there can't be a certain NATURAL type of justificaiton, a natural friendship with God. That is where the post-Tridentine theologian Melchior Cano, OP stated that infidels can be justified but not saved, where he's referring to a type of justification that can be achieved short of having the supernatural virtues, since infidels, lacking faith, cannot have the supernatural virtues. Theologians who discussed Trent on Justification stated that there are natural virtues they they call "fides initialis", "caritas initalis", "spes initialis", which are in fact natural analoguest to the respective supernatural virtues, and they can in fact develop these natural virtues, the natural equivalents of the supernatural ones by the same name, nay, they MUST develop these natural virtues in order to be led to the very point of receiving the SUPERNATURAL ones, which then only happens at the actual reception of the Sacrament of Baptism, which confers the supernatural virutes
ex opere operato. So while these natural virute are necessary dispositions to receive the freely-given unmerited supernatural equivalents, they do not somehow natural lead to, transition into or somehow merit the gift of the supernatural ones.