V. If Leo's legates in any way exceeded their instructions, they did so ineffectually.
Of course, if anything is alleged to have been done by those brethren whom I sent in my stead to the holy Synod, beyond that which was germane to the Faith, it shall be of no weight at all: because they were sent by the Apostolic See only for the purpose of extirpating heresy and upholding the Catholic Faith. For whatever is laid before bishops for inquiry beyond the particular subjects which come before synodal councils may admit of a certain amount of free discussion, if the holy Fathers have laid down nothing thereon at Nicæa. For anything that is not in agreement with their rules and constitutions can never obtain the assent of the Apostolic See. But how great must be the diligence with which this rule is kept, you will gather from the copies of the letter which we sent to the bishop of Constantinople, restraining his cupidity; and you shall take order that it reach the knowledge of all our brethren and fellow priests.
Source: Letters (New Advent)