Cite as: 585 U. S. ____ (2018) 21 Opinion of the Court stitutional, this would seriously and irreparably harm17 the State, and only an interlocutory appeal can protect that State interest. See Carson, supra, at 89–90. As a result, §1253 provides jurisdiction. III We now turn to the merits of the appeal. The primary question is whether the Texas court erred when it required the State to show that the 2013 Legislature somehow purged the “taint” that the court attributed to the defunct and never-used plans enacted by a prior legislature in 2011. A Whenever a challenger claims that a state law was enacted with discriminatory intent, the burden of proof lies with the challenger, not the State. Reno v. Bossier Parish School Bd., 520 U. S. 471, 481 (1997). This rule takes on special significance in districting cases. Redistricting “is primarily the duty and responsibility of the State,” and “[f]ederal-court review of districting legislation represents a serious intrusion on the most vital of local functions.” Miller v. Johnson, 515 U. S. 900, 915 (1995) (internal quotation marks omitted). “[I]n assessing the sufficiency of a challenge to a districting plan,” a court “must be sensitive to the complex interplay of forces that enter a legislature’s redistricting calculus.” Id., at 915– 916. And the “good faith of [the] state legislature must be presumed.” Id., at 915. The allocation of the burden of proof and the presumption of legislative good faith are not changed by a finding of past discrimination. “[P]ast discrimination cannot, in —————— 17 The dissent argues that we give “short shrift” to the irreparable harm question, post, at 16, but the inability to enforce its duly enacted plans clearly inflicts irreparable harm on the State, see, e.g., Maryland v. King, 567 U. S. 1301 (2012) (ROBERTS, C. J., in chambers).