The Seventh Ecumenical Council.  The Second Council of Nice 19Canon X.

That no cleric ought to leave his diocese and go into another without the knowledge of the Bishop.

Since certain of the clergy, misinterpreting the canonical constitutions, leave their own diocese and run into other dioceses, especially into this God-protected royal city, and take up their abode with princes, celebrating liturgies in their oratories, it is not permitted to receive such persons into any house or church without the license of their own Bishop and also that of the Bishop of Constantinople. And if any clerk shall do this without such license, and shall so continue, let him be deposed. With regard to those who have done this with the knowledge of the aforesaid Bishops, it is not lawful for them to undertake mundane and secular responsibilities, since this is forbidden by the sacred canons. And if anyone is discovered holding the office of those who are called Meizoteroi; let him either lay it down, or be deposed from the priesthood. Let him rather be the instructor of the children and others of the household, reading to them the Divine Scriptures, for to this end he received the priesthood.