eh....i'm surprised that language was included in the agreement.....without the consent of the sponsor.
it is not a sponsor's job to vouch for their sponsee, or to verify their "sobriety". AA is based on anonymity, and sponsor's role in one's recovery is/should be protected as well. for your ex to even name his sponsor is a violation of the principle of anonymity. sponsors should not be involved in the sponsee's divorce/parenting plan...that is way out of bounds.