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Rh Kagama, 118 U. S., at 381–382). In enacting ICWA, Congress affirmed this understanding. It recognized that “there is no resource that is more vital to the continued existence and integrity of Indian [T]ribes than their children.” 25 U. S. C. §1901(3). Yet it also recognized that the mass-removal of Indian children by States and other outsiders threatened the “continued existence and integrity of Indian [T]ribes.” Ibid.; see also §1901(4). By setting out to eliminate that practice, Congress sought to preserve the Indian-law bargain written into the Constitution’s text by securing the continued viability of the “third sovereign.” S. O’Connor, Remark, Lessons From the Third Sovereign: Indian Tribal Courts, 33 Tulsa L. J. 1 (1997).

No doubt, ICWA sharply limits the ability of States to impose their own family-law policies on tribal members. But as we have seen, state intrusions on tribal authority have been a recurring theme throughout American history. See Ablavsky 2014, at 1009–1037. Long ago, those intrusions led the framers to abandon the loophole-ridden Indian affairs provision in the Articles of Confederation and adopt in the Constitution a different arrangement that commits the management of tribal relations solely to the federal government. Id., at 1038–1051; see also Clinton 1995, at 1098–1165. Recognizing as much, this Court has consistently reaffirmed the Tribes’ “immunity from state and local control.” Arizona v. San Carlos Apache Tribe of Ariz., 463 U. S. 545, 571 (1983) (internal quotation marks omitted). If that immunity means anything, it must mean that States and others cannot use their own laws to displace federal Indian policy.

Nor is there any serious question that Congress has the power under the Indian Commerce Clause to enact protections against the removal of Indian children. Thankfully, Indian children are not (these days) units of commerce. Cf. Fletcher & Singel 897–898 (describing an early practice of enslaving Indian children). But at its core, ICWA restricts