Jus Divinum means divine law. While the term has its origins in the jurisprudence of ancient Rome, it is usually encountered by Presbyterians when something is spoken of as being established by an ordinance of God. The reader might come across the divine law or right of something, or that something is set by divine law or right (jure divino). And, usually, it is the divine right of church government.
There are two parts to church government by divine right or law. The first is that God has ordained that there be a government of the church which differs from that of the state or any other institution. The second is that God has ordained the form which that government is to take.
This is different from the way in which God has ordained the government of peoples and nations. Here, God has ordained that there be a government; however, He has not ordained a single form that it should take. There are monarchies, aristocracies, and democracies. There are dictatorships and republics. There are constitutions which blend aspects of these forms to create checks and balances or to make them more representative. Samuel Rutherford, for example, lists different forms of civil government and then states his preference for a limited and mixed monarchy. The form itself is not as important to him as the fact that it is founded upon some social contract.
Few today would deny that the church should have its own governing bodies, and few today would think that the form mattered. The old disputes between Episcopalians, Presbyterians, and Independents as to whose view is most biblical are of the past. The issue today is what works, situationally speaking. Here, influences from civil government or corporate business have carried over to the church. The discussion has moved on from the 17th century, but the question of jus divinum remains relevant.
The church is an absolute monarchy. It is neither limited nor mixed. Christ is its sole King and Head. He has imposed a constitution on it, not it on him. Jus divinum matters, because for the church, it is Rex lex, not lex rex.
The church is not a republic. This might be described as the Princeton problem. There is much of representative government and the efficient functioning of the executive branch in the thinking of Samuel Miller and Charles Hodge. Nor are the elderships of the church analogous to Congress or Parliament in their legislative functions. Though legislation is spoken of, elderships do not pass laws so much as they pass regulations to administer the law of the King.
The church is not a democracy. Elders are not tribunes of the people. Elections are not the method by which the people choose their rulers or representatives. They are the method by which they recognise the rulers and representatives Christ has gifted to them. Also, as all power is Christ’s and He gives it to elders to use ministerially,[1] there is no residual power in the people. And rule by consent has as much to do with Effectual Calling as it has to do with elderships acting clearly according to their divine mandate.
All authority is given to Christ, and He directed His apostles to teach others what He had taught them. From the word which they have left, the government of Christ’s church is to be by elders acting in graded elderships, that is by Ministers of the Word and Ruling Elders acting in the church courts of Kirk-sessions, Presbyteries, Synods, and General Assemblies; and their administration of that government is to be in accordance with His Kingship.
[1] For more detail see https://idgebbie.wixsite.com/presbyterianpicante/post/bannerman-s-third-theory