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ty in court while continuing to deny refunds and assess deficiencies introduces a complication. Given the Government's concession, amicus contends, once the District Court ordered the refund, the case should have ended and the appeal been dismissed. But this argument elides the distinction between Article III's jurisdictional requirements and the prudential limits on its exercise, which are "essentially matters of judicial self-governance." Warth v. Seldin, 422 U.S. 490, 500. Here, the United States retains a stake sufficient to support Article III jurisdiction on appeal and in this Court. The refund it was ordered to pay Windsor is "a real and immediate economic injury," Hein v. Freedom From Religion Foundation, Inc., 551 U.S. 587, 599, even if the Executive disagrees with §3 of DOMA. Windsor's ongoing claim for funds that the United States refuses to pay thus establishes a controversy sufficient for Article III jurisdiction. Cf. INS v. Chadha, 462 U.S. 919.
Prudential considerations, however, demand that there be "concrete adverseness which sharpens the presentation of issues upon which the court so largely depends for illumination of difficult constitutional questions." Baker v. Carr, 369 U.S. 186, 204. Unlike Article III requirements—which must be satisfied by the parties before judicial consideration is appropriate—prudential factors that counsel against hearing this case are subject to "countervailing considerations [that] may outweigh the concerns underlying the usual reluctance to exert judicial power." Warth, supra, at 500–501. One such consideration is the extent to which adversarial presentation of the issues is ensured by the participation of amici curiae prepared to defend with vigor the legislative act's constitutionality. See Chadha, supra, at 940. Here, BLAG's substantial adversarial argument for §3's constitutionality satisfies prudential concerns that otherwise might counsel against hearing an appeal from a decision with which the principal parties agree. This conclusion does not mean that it is appropriate for the Executive as a routine exercise to challenge statutes in court instead of making the case to Congress for amendment or repeal. But this case is not routine, and BLAG's capable defense ensures that the prudential issues do not cloud the merits question, which is of immediate importance to the Federal Government and to hundreds of thousands of persons. Pp. 5–13.
DOMA is unconstitutional as a deprivation of the equal liberty of persons that is protected by the Fifth Amendment. Pp. 13–26.
(a) By history and tradition the definition and regulation of marriage has been treated as being within the authority and realm of the separate States. Congress has enacted discrete statutes to regulate the meaning of marriage in order to further federal policy, but DOMA, with a directive applicable to over 1,000 federal statutes and
