The model and archetype for any earthly kingship is that of Christ the King. And as the “First Laymen of the Realm”, Catholic Kings had a quasi-priestly role. The Holy Roman Emperor(King of Germany) a Canon of Saint Peter’s; the King of France was a Canon of Saint John Lateran and of Saint Peter’s(this title is technically held by the President of the French Republic, but no French President that I am aware of has actually acted as deacon or sub-deacon in Papal masses, like the Kings of France sometimes did); the King of England was the Canon of Saint Paul Outside the Walls.
For well over 1000 years the Church gave its approval of the institution of monarchy by crowning and anointing kings with with sacred oil. I have heard people say, and I suspect that many more believe, that the “modern church” is one of democracy and freedom, etc., blah, blah, blah…
You cannot escape the fact that the Church explicitly condoned and endorsed monarchy, and conferred many graces to many different men(and women)
Here is the coronation oath from the most recent Pontificale Romanum to contain coronation rites(pre-1968).
Latin:
Ego N. Deo annuente, futurus Rex N. profiteor, et promitto coram Deo et Angelis ejus deinceps legem, justitiam et pacem
Ecclesiae Dei, populoque mihi subjecto pro posse et nosse, facere ac servare, salvo condigno misericordiae Dei respectu,
sicut in consilio fidelium meorum melius potero invenire. Pontificibus quoque Ecclesiarum Dei, condignum et canonicum
honorem exhibere; atque ea, quae ab Imperatoribus, et Regibus Ecclesiis collata, et reddita sunt, inviolabiliter observare.
Abbatibus, Comitibus et Vasaliis meis congruum honorem, secundum consilium fidelium meorum praestare.
English:
I, N., with God’s consent the future King N., profess and promise in the presence of God and his Angels to bring about and
maintain law, justice and peace, as far as I am able to do so, in the Church of God and in the nation subject to me,
having a fitting respect for the mercy of God, as best I can devise in accordance with the counsel of my faithful subjects.
I will also give due and canonical honour to the Bishops of the Churches of God and preserve involate those things
which have been conferred upon and rendered to the Churches by Emperors and Kings. I will give fitting honour to my
Abbots, Counts and Vassals in accordance with the counsel of my faithful subjects.
Sources:
youtube.com/watch?v=pNqTNgjiyUE (Wise and helpful lecture on Chivalry)
Pontificale Romanum
religiousstudiesblog.blogspot.com/2011/03/traditional-catholic-coronation-rite.html