"It appertaineth not to thee King Uzziah to burn incense unto the Lord but to the priests of Aaron." The Westminster Divines were not Erastian and OT Israel was not Erastian, unfortunately many contemporary Presbyterians are Erastian in their presuppositions. Ironically, in the historic debate against Erastianism by Presbyterians the argument was that church & state were distinct in Israel and now those that hold such a view are accused by fellow Presbyterians of being Erastian.
Ditto to Peter and Chris Rhoades.
The Two Sons of Oil; or, The Faithful Witness for Magistracy and Ministry upon a Scriptural Basis by Samuel B. Wylie