After the California Supreme Court held that limiting marriage to opposite-s** couples violated the California Constitution, state voters pa**ed a ballot initiative known as Proposition 8, amending the State Constitution to define marriage as a union between a man and a woman. Respondents, same-s** couples who wish to marry, filed suit in federal court, challenging Proposition 8 under the Due Process and Equal Protection Clauses of the Fourteenth Amendment, and naming as defendants California's Governor and other state and local officials responsible for enforcing California's marriage laws. The officials refused to defend the law, so the District Court allowed petitioners—the initiative's official proponents—to intervene to defend it. After a bench trial, the court declared Proposition 8 unconstitutional and enjoined the public officials named as defendants from enforcing the law. Those officials elected not to appeal, but petitioners did. The Ninth Circuit certified a question to the California Supreme Court: whether official proponents of a ballot initiative have authority to a**ert the State's interest in defending the constitutionality of the initiative when public officials refuse to do so. After the California Supreme Court answered in the affirmative, the Ninth Circuit concluded that petitioners had standing under federal law to defend Proposition 8's constitutionality. On the merits, the court affirmed the District Court's order.
Held: Petitioners did not have standing to appeal the District Court's order. Pp. 5–17.
(a) Article III of the Constitution confines the judicial power of federal courts to deciding actual “Cases” or “Controversies.” §2. One essential aspect of this requirement is that any person invoking the power of a federal court must demonstrate standing to do so. In other words, the litigant must seek a remedy for a personal and tangible harm. Although most standing cases consider whether a plaintiff has satisfied the requirement when filing suit, Article III demands that an “actual controversy” persist throughout all stages of litigation. Already, LLC v. Nike, Inc., 568 U. S. ___, ___. Standing “must be met by persons seeking appellate review, just as it must be met by persons appearing in courts of first instance.” Arizonans for Official English v. Arizona, 520 U. S. 43, 64. The parties do not contest that respondents had standing to initiate this case against the California officials responsible for enforcing Proposition 8. But once the District Court issued its order, respondents no longer had any injury to redress, and the state officials chose not to appeal. The only individuals who sought to appeal were petitioners, who had intervened in the District Court, but they had not been ordered to do or refrain from doing anything. Their only interest was to vindicate the constitutional validity of a generally applicable California law. As this Court has repeatedly held, such a “generalized grievance”—no matter how sincere—is insufficient to confer standing. See Lujan v. Defenders of Wildlife, 504 U. S. 555, 573–574. Petitioners claim that the California Constitution and election laws give them a “ ‘unique,' ‘special,' and ‘distinct' role in the initiative process,” Reply Brief 5, but that is only true during the process of enacting the law. Once Proposition 8 was approved, it became a duly enacted constitutional amendment. Petitioners have no role—special or otherwise—in its enforcement. They therefore have no “personal stake” in defending its enforcement that is distinguishable from the general interest of every California citizen. No matter how deeply committed petitioners may be to upholding Proposition 8, that is not a particularized interest sufficient to create a case or controversy under Article III. Pp. 5–9.
(b) Petitioners' arguments to the contrary are unpersuasive. Pp. 9– 16.
(1) They claim that they may a**ert the State's interest on the State's behalf, but it is a “fundamental restriction on our authority” that “[i]n the ordinary course, a litigant . . . cannot rest a claim to relief on the legal rights or interests of third parties.” Powers v. Ohio, 499 U. S. 400, 410. In Diamond v. Charles, 476 U. S. 54, for example, a pediatrician engaged in private practice was not permitted to defend the constitutionality of Illinois' abortion law after the State chose not to appeal an adverse ruling. The state attorney general's “letter of interest,” explaining that the State's interest in the proceeding was “ ‘essentially co-terminous with' ” Diamond's position, id., at 61, was insufficient, since Diamond was unable to a**ert an injury of his own, id, at 65. Pp. 9–10.
(2) Petitioners contend the California Supreme Court's determination that they were authorized under California law to a**ert the State's interest in the validity of Proposition 8 means that they “need no more show a personal injury, separate from the State's indisputable interest in the validity of its law, than would California's Attorney General or did the legislative leaders held to have standing in Karcher v. May, 484 U. S. 72 (1987).” Reply Brief 6. But far from supporting petitioners' standing, Karcher is compelling precedent against it. In that case, after the New Jersey attorney general refused to defend the constitutionality of a state law, leaders of New Jersey's Legislature were permitted to appear, in their official capacities, in the District Court and Court of Appeals to defend the law. What is significant about Karcher, however, is what happened after the Court of Appeals decision. The legislators lost their leadership positions, but nevertheless sought to appeal to this Court. The Court held that they could not do so. Although they could participate in the lawsuit in their official capacities as presiding officers of the legislature, as soon as they lost that capacity, they lost standing. Id., at 81. Petitioners here hold no office and have always participated in this litigation solely as private parties. Pp. 10–13.
(3) Nor is support found in dicta in Arizonans for Official English v. Arizona, supra. There, in expressing “grave doubts” about the standing of ballot initiative sponsors to defend the constitutionality of an Arizona initiative, the Court noted that it was “aware of no Arizona law appointing initiative sponsors as agents of the people of Arizona to defend, in lieu of public officials, the constitutionality of initiatives made law of the State.” Id., at 65. Petitioners argue that, by virtue of the California Supreme Court's decision, they are authorized to act as “agents of the people of California.” Brief for Petitioners 15. But that Court never described petitioners as “agents of the people.” All the California Supreme Court's decision stands for is that, so far as California is concerned, petitioners may “a**ert legal arguments in defense of the state's interest in the validity of the initiative measure” in federal court. 628 F. 3d 1191, 1193. That interest is by definition a generalized one, and it is precisely because proponents a**ert such an interest that they lack standing under this Court's precedents. Petitioners are also plainly not agents of the State. As an initial matter, petitioners' newfound claim of agency is inconsistent with their representations to the District Court, where they claimed to represent their own interests as official proponents. More to the point, the basic features of an agency relationship are missing here: Petitioners are not subject to the control of any principal, and they owe no fiduciary obligation to anyone. As one amicus puts it, “the proponents apparently have an unelected appointment for an unspecified period of time as defenders of the initiative, however and to whatever extent they choose to defend it.” Brief for Walter Dellinger 23. Pp. 13–16.
(c) The Court does not question California's sovereign right to maintain an initiative process, or the right of initiative proponents to defend their initiatives in California courts. But standing in federal court is a question of federal law, not state law. No matter its reasons, the fact that a State thinks a private party should have standing to seek relief for a generalized grievance cannot override this Court's settled law to the contrary. Article III's requirement that a party invoking the jurisdiction of a federal court seek relief for a personal, particularized injury serves vital interests going to the role of the Judiciary in the federal system of separated powers. States cannot alter that role simply by issuing to private parties who otherwise lack standing a ticket to the federal courthouse. Pp. 16–17.
671 F. 3d 1052, vacated and remanded.
ROBERTS, C. J., delivered the opinion of the Court, in which SCALIA, GINSBURG, BREYER, and KAGAN, JJ., joined. KENNEDY, J., filed a dissenting opinion, in which THOMAS, ALITO, and SOTOMAYOR, JJ., joined.