The Reign of Christ the King demands that civil laws enshrine the dictates of Christ through whose wisdom the universe was made and by whose providence it continues to operate.
The document penned at Vatican II on religious liberty, Dignitatis Humanae (DH), sums up the reign of Christ the King as follows: "[T]he highest norm of human life is the divine law — eternal, objective and universal — whereby God orders, directs and governs the entire universe and all the ways of the human community by a plan conceived in wisdom and love."
The document, DH, begins with a statement that preserves previous Catholic teaching on religious freedom and the reign of Christ the King in society. Paragraph one attests, "Religious freedom ... has to do with immunity from coercion in civil society. Therefore, it leaves untouched traditional Catholic doctrine on the moral duty of men and societies toward the true religion and toward the one Church of Christ."
Part of that traditional Catholic doctrine came from the famous encyclical written in 1925 by Pope Pius XI called Quas Primas on the social kingship of Christ. In it, Pius XI isn't ordering civil leaders to make converts to Catholicism but is, rather, demanding that they make just laws in keeping with the moral order created by Christ: "[H]is kingly dignity demands that the state should take account of the commandments of God and of Christian principles, both in making laws and in administering justice and also in providing for the young a sound moral education."
Watch the panel discuss how civil rulers must honor God by respecting His laws in The Download—Christ the King.