42 CFR §2.17

1. (a)Restrictions on placement. Except as specifically authorized by a court order granted under § 2.67, no part 2 program may knowingly employ, or enroll as a patient, any undercover agent or informant.
2. (b)Restriction on use and disclosure of information. No information obtained by an undercover agent or informant, whether or not that undercover agent or informant is placed in a part 2 program pursuant to an authorizing court order, may be used or disclosed to criminally investigate or prosecute any patient.