Bless, Father!
Certainly, in all cases Rome would have to approve the cultus of those venerated in Christian communities (coming into union with Rome) who have their request for continued veneration of those person approved by Rome. The fact of their popular veneration can meet the requirement leading to Beatification (as occurred with the English Martyrs and with Blessed Kateri Tekakwitha - whose miracles were not recorded, but her long-standing veneration was sufficient for her beatification).
Perhaps this will prove true for King Charles and King Henry. And I don’t know what King Henry’s status currently is other than the fact that members of his society can publicly invoke him as “Blessed King Henry” (whatever that means in the long run).
Here is the link for what was the Society of King Henry VI and is now “Eton Cambridge and Associates, Henry VI:”
www.ecah.co.uk
And the Society of King Charles the Martyr:
www.skcm.org
In the case of King Henry, that is a “straight” Cause for Catholic canonization.
In King Charles’ case, it would be a Roman approval for continued veneration of King Charles by the Anglican Use people coming into union with Rome. Rome has issued nothing on this matter to date, but I know that this is being worked on at Rome as these High Church Anglicans could not conceive of their spiritual life without Blessed Charles (as they call him).
Certainly, there have been and are many Catholic saints who are not approved by Rome but who are locally venerated in Italy and elsewhere as a result of their having been beatified locally at some point in history by a bishop or regional bishops acting together - and this after the bull promulgated by Pope Urban VIII by which he reserved beatifications to Rome alone.
Blessed John Duns Scotus was locally beatified by an Italian bishop and was venerated as “Blessed John” for years before the Ven. Pope John Paul beatified him.
I’ve come across four volumes of photographs of such saints in a university library - “Blessed Peter Lombard” is among them.
The case of “Blessed Jerome Savonarola” is particularly fascinating, given the Dominican Order’s historic promotion of his cultus with medals and relics. St Philip Neri, when he died, was found with a relic-medal of Savonarola’s around his neck and when this was reported to the Pope during his canonization cause, the Pope told them to pass over it and proceed. Moreover, I found that one of Savonarola’s students left Italy and went to Russia where he became a Russian Orthodox monk who spent a good deal of his life writing against the “spiritually corrupt West.” He was himself canonized by the Orthodox Church in 1988 as “St Maximus the Greek” and in his service, Savonarola is referred to by the Orthodox as “Blessed Jerome.”
Getting back to the Anglicans, the High Church Anglicans are quite serious about their canonizations, local as they are. In Lincolnshire, I believe, there is the cult of “Edward King, Bishop and Saint” honoured on May 8th and there is a statue of him alongside those of St Hugh of Lincoln and others (he suffered greatly for his devotion to Catholic forms of worship and articles of faith). There is “St Arthur Cripps” of Central Africa, “Blessed James DeKoven” in the U.S. around whom a religious community has been organized (The Solitaries of DeKoven), the former community of Christ the Sower who honoured “St Nicholas Ferrar of Little Gidding,” Blessed Charles Lowder of the Society of the Holy Cross (honoured on September 9th) who organized charitable works in London for the poor victims of industrialization in the 19th century (he held High Church services in the streets and was pelted with rocks and fruit for being “popish”).
Near where I live is an Anglican community of nuns that works in hospitals founded by Hannah Grier Coombe and they have an icon of her in their chapel. The Anglican Benedictine Holy Cross Order founded by James Otis Sargent Huntington honours their founder as a saint and invokes him in their public litanies (there is a monastery of theirs here in Toronto).
Reading the lives of these Anglican worthies, who were Catholic in every which way, defended (and suffered for) the Immaculate Conception of our Lady, Eucharistic Adoration, veneration of the Crucifix, the sacrificial nature of the Mass, celibacy and even the primacy of honour of the pope of Rome - they seem to me to be very deserving of continued veneration by those of their church who see them as true temples of the Holy Spirit.
As one French Catholic priest once put it, “The Anglicans I know are very devoted to Eucharistic Adoration - and even if they do not have a valid Eucharist, they really do pray to our Eucharistic Lord as that is their intention.”
Enough out of me, Father!
Alex