J.B. and W.J., an unmarried couple, were enrolled members of the Mississippi Band of Choctaw Indians (Tribe) (plaintiff). After J.B. became pregnant with twins, J.B. and W.J. left their respective homes on the Choctaw Reservation and traveled over 200 miles to give birth to the children, B.B. and G.B. Subsequently, J.B. and W.J. each signed forms consenting to the adoption of the twins by Orrey and Vivian Holyfield (defendants). The Holyfields filed a petition for adoption, which was granted by a chancery court. The Tribe filed a motion to vacate the adoption decree on the ground that the chancery court lacked the authority and jurisdiction to issue the adoption pursuant to the Indian Child Welfare Act (ICWA), 25 U.S.C. §§ 1901-1963. The chancery court rejected the Tribe’s motion, holding that the Tribe never obtained exclusive jurisdiction over the children. The Tribe appealed. The Supreme Court of Mississippi affirmed, concluding that J.B. and W.J. had abandoned the children by relinquishing them for adoption and that the domicile of the children was that of the adults who stood in loco parentis to the children, namely the Holyfields. The United States Supreme Court granted certiorari to review.