25 U.S.C. § 1951 : US Code - Section 1951: Information availability to and disclosure by Secretary

    (a) Copy of final decree or order; other information; anonymity
      affidavit; exemption from Freedom of Information Act
      Any State court entering a final decree or order in any Indian
    child adoptive placement after November 8, 1978, shall provide the
    Secretary with a copy of such decree or order together with such
    other information as may be necessary to show - 
        (1) the name and tribal affiliation of the child;
        (2) the names and addresses of the biological parents;
        (3) the names and addresses of the adoptive parents; and
        (4) the identity of any agency having files or information
      relating to such adoptive placement.

    Where the court records contain an affidavit of the biological
    parent or parents that their identity remain confidential, the
    court shall include such affidavit with the other information. The
    Secretary shall insure that the confidentiality of such information
    is maintained and such information shall not be subject to the
    Freedom of Information Act (5 U.S.C. 552), as amended.
    (b) Disclosure of information for enrollment of Indian child in
      tribe or for determination of member rights or benefits;
      certification of entitlement to enrollment
      Upon the request of the adopted Indian child over the age of
    eighteen, the adoptive or foster parents of an Indian child, or an
    Indian tribe, the Secretary shall disclose such information as may
    be necessary for the enrollment of an Indian child in the tribe in
    which the child may be eligible for enrollment or for determining
    any rights or benefits associated with that membership. Where the
    documents relating to such child contain an affidavit from the
    biological parent or parents requesting anonymity, the Secretary
    shall certify to the Indian child's tribe, where the information
    warrants, that the child's parentage and other circumstances of
    birth entitle the child to enrollment under the criteria
    established by such tribe.