Franciscus is essentially a King in the Catholic Monarchial institution and he is also King of Vatican City and even though he has Bishops and can call Synods, Ecumenical Councils etc etc, he can- -and does- rule as a King whenever he thinks that is a just and necessary thing.
Note that in Christ there were five things necessary for a king, so that he could rightly and correctly claim kinship: (1) That he was constituted by a superior, not forcing his way in of his own accord; so here he says he was constituted by God. 1 Kings 1 tells how David appointed his son Solomon as king. —Heb 5:4 No one takes, that is, should take, this honor on himself etc. (2) He should have clemency, so that he will be a king, not a tyrant. —Prov 20:28 Loyalty and faithfulness preserve the king, and his throne is upheld by righteousness. —1 Kings 20:31 The kings of Israel are clement. (3) Justice or (4) courage is also required. —Sirach 7:6 Do not seek to become a judge, if you are unable to root out injustice. —Deut 1:16—17 Judge rightly between one person and another, whether citizen or resident alien. You must not be partial in judging: hear out the small and the great alike; you shall not be intimidated by anyone, for the judgment is God's. But of Christ it was said in Isaiah 11:3 He shall not judge by what his eyes see, or decide by what his ears hear; but with righteousness he shall judge the poor. (5) Wisdom is also necessary. That is why Solomon asked God for wisdom before accepting kingship (1 Kings 3). But of Christ the Apostle says in 1 Cor 1:24 We preach Christ the power of God and the wisdom of God.
Over Zion his holy mountain. By Zion, which is the upper part of the city of Jerusalem, the capital of Judaea, is understood the Church of the Jews, that small early Church which Christ and the Apostles gathered. It is rightly called a mountain, because of the firmness of faith of its members. —Psalm 124:1 Those who trust in the Lord are like Mount Zion etc.— and also because they were so elevated in virtue. —Isaiah 2:2 The mountain of the Lord's house shall be established as the highest of the mountains. — and also because they were the first to receive the rays of faith and transmit them to others. —Psalm 76:4 You are bright, majestic from the everlasting mountains (Vul), that is the holy Apostles and the first members of the Church.
Preaching his commandment. This is the purpose for which he was made king, that is, to teach and preach. —Ez 3:17 Son of man, I have made you a sentinel for the house of Israel. —Ez 34:23 I will set up over them one shepherd, my servant David, and he shall feed them with knowledge and doctrine. That is what Christ did. —Mat 4:23 Jesus went throughout Galilee proclaiming the good news of the kingdom. If he was put in office for this, his vicars should be put in office for the same purpose. Gregory said (Letter 24): "If a pastor does not know how to preach, he has usurped the office of priesthood." —Mat 24:45 and Luke 12:42 Who do you think is the faithful and wise servant whom the Lord has set over his family? etc. They are not put in office to multiply horses and family dependents. —Deut 17:16 He must not acquire many horses for himself, or return the people to Egypt in order to acquire more horses. Therefore Prov 6:1 says My child, if you have given your pledge to your neighbor hurry and plead etc.
He must preach the commandment, and not his own discoveries and achievements. The commandment is that of charity, as Christ preached. —John 13:34 I give you a new commandment, that you love one another. This is said to be one commandment, because on it depends everything else in Scripture. —Mat 22:40 On these two commandments depend the whole Law and the Prophets.