IX. Translation from one see to another is to be prohibited.
If any bishop, despising the insignificance of his city, shall intrigue for the government of a more populous place, and transfer himself by whatever means to a larger flock, he shall first be driven from the chair he has usurped, and also shall be deprived of his own: so shall he preside neither over those whom in his greed he coveted, nor over those whom in his arrogance he spurned. Therefore let each be content with his own bounds, and not seek to be raised above the limits of his present post.
Source: Letters (New Advent)