25 U.S.C. § 1919: Agreements between States and Indian tribes

States and Indian tribes are authorized to enter into agreements with each other respecting care and custody of Indian children and jurisdiction over child custody proceedings, including agreements which may provide for orderly transfer of jurisdiction on a case-by-case basis and agreements which provide for concurrent jurisdiction between States and Indian tribes. Such agreements may be revoked by either party upon one hundred and eighty days’ written notice to the other party. Such revocation shall not affect any action or proceeding over which a court has already assumed jurisdiction, unless the agreement provides otherwise.