Page:Haaland v. Brackeen.pdf/6

6 them to apply the placement preferences in making custody determinations. §§§ [sic]1915(a), (b). But Congress can require state courts, unlike state executives and legislatures, to enforce federal law. See New York v. United States, 505 U. S. 144, 178–179. Petitioners draw a distinction between requiring state courts to entertain federal causes of action and requiring them to apply federal law to state causes of action, but this argument runs counter to the Supremacy Clause. When Congress enacts a valid statute, “state law is naturally preempted to the extent of any conflict with a federal statute.” Crosby v. National Foreign Trade Council, 530 U. S. 363, 372. That a federal law modifies a state law cause of action does not limit its preemptive effect. See, e.g., Hillman v. Maretta, 569 U. S. 483, 493–494 (federal law establishing order of precedence for life insurance beneficiaries preempted state law). Pp. 23–25.

(a) The individual petitioners argue that ICWA’s hierarchy of preferences injures them by placing them on unequal footing with