The power or authority of church government is a spiritual power. Spiritual, not so perfectly and completely as Christ’s supreme government is spiritual, Who alone has absolute and immediate power and authority over the very spirits and consciences of men, ruling them by the invisible influence of His Spirit and grace as He pleases (John 3:8; Rom. 8:14; Gal. 2:20), but so purely, properly, and merely spiritual is this power that it really, essentially and specifically differs, and is contradistinct from that power which is properly civil, worldly and political, in the hand of the civil magistrate. Now, this power of church government is in this sense properly, purely, merely spiritual, and that may be evidenced many ways according to Scripture. Accordingly, the rule, fountain, matter, form, subject, object, end, and all of this power is only spiritual.

Jus Divinum Regiminis Ecclesiastici, (Naphtali Press Special Editions, volume II), 103.

Synods and councils are to handle, or conclude, nothing, but that which is ecclesiastical: and are not to intermeddle with civil affairs which concern the commonwealth; unless by way of humble petition, in cases extraordinary; or by way of advice, for satisfaction of conscience, if they be thereunto required by the civil magistrate.

Westminster Confession of Faith (1647), 31.5.