25 U.S.C. § 2813
The Director of the Office of Justice Services or the Director of the Indian Health Service, as appropriate (referred to in this section as the "Director concerned"), shall approve or disapprove, in writing, any request or subpoena from a tribal or State court for a law enforcement officer, sexual assault nurse examiner, or other employee under the supervision of the Director concerned to provide documents or testimony in a deposition, trial, or other similar criminal proceeding regarding information obtained in carrying out the official duties of the employee.
The court issuing a subpoena under paragraph (1) shall provide to the appropriate Federal employee (or agency in the case of a document request) notice regarding the request to provide testimony (or release a document) by not less than 30 days before the date on which the testimony will be provided.
The Director concerned shall approve a request or subpoena under subsection (a) if the request or subpoena does not violate the policy of the Department to maintain impartiality.
If the Director concerned fails to approve or disapprove a request or subpoena for testimony or release of a document by the date that is 30 days after the date of receipt of notice of the request or subpoena, the request or subpoena shall be considered to be approved for purposes of this section.
25 U.S.C. § 2813