In the aftermath of the September 11, 2001, terrorist attacks, the Central Intelligence Agency believed that Abu Zubaydah was a senior al Qaeda lieutenant likely to possess knowledge of future attacks against the United States. Zubaydah—currently a detainee at the Guantánamo Bay Naval Base—says that in 2002 and 2003 he was held at a CIA detention site in Poland, where he was subjected to “enhanced interrogation” techniques. In 2010, Zubaydah filed a criminal complaint in Poland, seeking to hold accountable any Polish nationals involved in his alleged mistreatment at the CIA site ostensibly located in that country. The United States denied multiple requests by Polish prosecutors for information related to Zubaydah’s claim on the ground that providing such information would threaten national security. Zubaydah filed a discovery application pursuant to 28 U. S. C. §1782, which permits district courts to order production of testimony or documents “for use in a proceeding in a foreign . . . tribunal.” Zubaydah asked for permission to serve two former CIA contractors with subpoenas requesting information regarding the alleged CIA detention facility in Poland and Zubaydah’s treatment there. The Government intervened and asserted the state secrets privilege in opposition to Zubaydah’s discovery request.

   The District Court rejected the Government’s claim that merely confirming that a detention site was operated in Poland would threaten national security. The District Court nevertheless dismissed Zubaydah’s discovery application. It concluded that the state secrets privilege applied to operational details concerning the CIA’s cooperation with a foreign government, and that meaningful discovery could not proceed without disclosing privileged information. On appeal, the Ninth Circuit agreed with the District Court that much of the information sought by Zubaydah was protected from disclosure by the state secrets privilege, but the panel majority concluded that the District Court had erred when it dismissed the case. It believed that the state secrets privilege did not apply to publicly known information. The panel majority also concluded that because the CIA contractors were private parties and not Government agents, they could not confirm or deny anything on the Government’s behalf. Given these holdings, the panel majority determined that discovery into three topics could continue: the existence of a CIA detention facility in Poland, the conditions of confinement and interrogation at that facility, and Zubaydah’s treatment at that location.

Held: The judgment is reversed, and the case is remanded.

938 F. 3d 1123, reversed and remanded.

  Justice Breyer delivered the opinion of the Court with respect to all but Parts II–B–2 and III, concluding that, in the context of Zubaydah’s §1782 discovery application, the Court of Appeals erred in holding that the state secrets privilege did not apply to information that could confirm or deny the existence of a CIA detention site in Poland. Pp. 7–13, 14–15, 18.

  (a) The state secrets privilege permits the Government to prevent disclosure of information when that disclosure would harm national security interests. United States v. Reynolds, 345 U. S. 1, 10–11. To assert the privilege, the Government must submit to the court a “formal claim of privilege, lodged by the head of the department which has control over the matter.” Id., at 7–8. “The court itself must determine whether the circumstances are appropriate for the claim of privilege.” Id., at 8. However, in making that determination, a court should exercise its traditional “reluctan[ce] to intrude upon the authority of the Executive in military and national security affairs,” Department of Navy v. Egan, 484 U. S. 518, 530. If the Government has offered a valid reason for invoking the privilege, “the showing of necessity” by the party seeking disclosure of the ostensibly privileged information will “determine how far the court should probe in satisfying itself that the occasion for invoking the privilege is appropriate.” Reynolds, 345 U. S., at 11. The narrow evidentiary dispute before the Court asks how these principles apply to Zubaydah’s specific discovery requests. Pp. 7–9.

  (b) In certain circumstances, the Government may assert the state secrets privilege to bar the confirmation or denial of information that has entered the public domain through unofficial sources. Here, the information held by the Ninth Circuit to be nonprivileged would necessarily tend to confirm (or deny) that the CIA maintained a detention site in Poland. The Government has shown that such information— even if already made public through unofficial sources—could significantly harm national security. The CIA Director stated in his declaration that “clandestine” relationships with foreign intelligence services are “critical” and “based on mutual trust that the classified existence and nature of the relationship will not be disclosed.” App. to Pet. for Cert. 135a–136a. Given the nature of Zubaydah’s specific discovery requests there is a reasonable danger that in this case a former CIA insider’s confirmation of confidential cooperation between the CIA and a foreign intelligence service could badly damage the CIA’s clandestine relationships with foreign authorities. Pp. 9–13.

  (c) The CIA contractors’ confirmation (or denial) of the information Zubaydah seeks would be tantamount to disclosure by the CIA itself. The contractors worked directly for the CIA and had a central role in the events in question. The CIA Director describes the harm that would result from the contractors responding to the subpoenas, not the risks of a response from the CIA (or any other CIA official or employee). Pp. 14–15.

  (d) Zubaydah’s need for location information is not great, perhaps close to nonexistent. At oral argument, he suggested that he did not seek confirmation of the detention site’s Polish location so much as he sought information about what had happened there. P. 15.

  (e) Here, the state secrets privilege applies to the existence (or nonexistence) of a CIA facility in Poland, and therefore precludes further discovery into all three categories of information the Ninth Circuit concluded to be nonprivileged. P. 15.

  (f) This case is remanded with instructions to dismiss Zubaydah’s current application for discovery under §1782. P. 18.

 Breyer, J., delivered the opinion of the Court, except as to Parts II–B–2 and III. Roberts, C. J., joined that opinion in full, Kavanaugh and Barrett, JJ., joined as to all but Part II–B–2, Kagan, J., joined as to all but Parts III and IV and the judgment of dismissal, and Thomas and Alito, JJ., joined Part IV. Thomas, J., filed an opinion concurring in part and concurring in the judgment, in which Alito, J., joined. Kavanaugh, J., filed an opinion concurring in part, in which Barrett, J., joined. Kagan, J., filed an opinion concurring in part and dissenting in part. Gorsuch, J., filed a dissenting opinion, in which Sotomayor, J., joined.

EMW Women’s Surgical Center and two of its doctors filed a federal suit seeking to enjoin enforcement of Kentucky House Bill 454, legislation regulating the abortion procedure known as dilation and evacuation. Named defendants in EMW’s lawsuit included two Commonwealth officials, the attorney general and the cabinet secretary for Health and Family Services. EMW agreed to dismiss claims against the attorney general without prejudice. The stipulation of dismissal specified that the attorney general’s office reserved “all rights, claims, and defenses . . . in any appeals arising out of this action” and agreed to be bound by “any final judgment . . . subject to any modification, reversal or vacation of the judgment on appeal.” App. 28–30. The secretary remained in the case and defended the challenged law. After a bench trial, the District Court held that HB 454 unconstitutionally burdens a woman’s right to an abortion and issued a permanent injunction against the law’s enforcement.

   The secretary filed a notice of appeal.  While the appeal was pending, Kentucky elected a new attorney general, petitioner David Cameron, and elected the former attorney general, Andrew Beshear, Governor. Governor Beshear appointed a new secretary for Health and Family Services who continued the defense of HB 454 on appeal. Prior to oral argument before the Sixth Circuit, Attorney General Cameron entered an appearance as counsel for the new secretary. A divided Sixth Circuit panel affirmed the District Court’s judgment. The secretary then informed the attorney general’s office that the secretary would not file a petition for rehearing en banc or a petition for a writ of certiorari challenging the Sixth Circuit panel’s decision. Two days later, the attorney general moved to withdraw as counsel for the secretary and to intervene as a party on the Commonwealth’s behalf. The secretary did not oppose that motion, but respondents did. The attorney general also filed a petition for rehearing en banc within the 14-day deadline for an existing party to seek rehearing. The Sixth Circuit denied the attorney general’s motion to intervene. This Court granted certiorari limited to the question whether the Sixth Circuit should have permitted the attorney general to intervene.

Held: The Court of Appeals erred in denying the attorney general’s motion to intervene. Pp. 4–13.

  (a) This Court has jurisdiction to consider whether the attorney general’s motion to intervene should have been granted notwithstanding respondents’ contention that the motion was jurisdictionally barred. See Arbaugh v. Y & H Corp., 546 U. S. 500, 506. Respondents concede that a court of appeals generally has jurisdiction to consider a non-party’s motion to intervene in a pending appeal. But respondents assert that a narrow subset of non-parties—those bound by the district court judgment—must file a timely notice of appeal to obtain appellate review and may not circumvent applicable jurisdictional time limits by filing a motion to intervene after the deadline for filing a notice of appeal has passed. Applying this theory, respondents contend that because the attorney general could have filed a notice of appeal but failed to do so within the time allowed by law, his motion for intervention should be treated like an untimely notice of appeal over which the Sixth Circuit lacked jurisdiction. Pp. 4–7.

   (1) No provision of law limits the jurisdiction of the courts of appeals to entertain a motion for intervention filed by a non-party in this way, even assuming that party can be bound by the judgment that is appealed. Unless clear from its language, a statute or rule does not impose a jurisdictional requirement. Henderson v. Shinseki, 562 U. S. 428, 439. Here, respondents cite no provision that deprives a court of appeals of jurisdiction in the way they suggest, and no such supporting language can be found in 28 U. S. C. §2107, Federal Rules of Appellate Procedure 3 and 4, or any other provision of law. Pp. 5–6.

   (2) This Court refuses to adopt what would essentially be a categorical claims-processing rule barring consideration of the attorney general’s motion. When a non-party enters into an agreement to be bound by a judgment in accordance with the agreement’s terms, it is hard to see why the non-party should be precluded from seeking intervention on appeal if the agreement preserves that opportunity. Here, the attorney general reserved “all rights, claims, and defenses . . . in any appeals arising out of this action.” That easily covers the right to seek rehearing en banc and the right to file a petition for a writ of certiorari. And that agreement makes clear that the judgment to which the attorney general agreed to be bound was the judgment that emerged after all appellate review concluded. Pp. 6–7.

  (b) Turning to the question whether the Court of Appeals properly denied the attorney general’s motion to intervene, the Court notes that no statute or rule provides a general standard to apply in deciding whether intervention on appeal should be allowed. Guided by the “policies underlying intervention” in the district courts, Automobile Workers v. Scofield, 382 U. S. 205, 217, n. 10, including the legal “interest” that a party seeks to “protect” through intervention on appeal, Fed. Rule Civ. Proc. 24(a)(2), the Court concludes that the Sixth Circuit erred in denying the attorney general’s motion to intervene. Pp. 7–13.

   (1) Resolution of a motion for permissive intervention is committed to the discretion of the court before which intervention is sought, see Automobile Workers, 382 U. S., at 217, n. 10; Fed. Rule Civ. Proc. 24(b)(1)(a). But a court fails to exercise its discretion soundly when it “base[s] its ruling on an erroneous view of the law,” Cooter & Gell v. Hartmarx Corp., 496 U. S. 384, 405, and that is what happened here. The Sixth Circuit panel failed to account for the strength of the Kentucky attorney general’s interest in taking up the defense of HB 454 when the secretary elected to acquiesce. A State “clearly has a legitimate interest in the continued enforceability of its own statutes,” Maine v. Taylor, 477 U. S. 131, 137, and a State’s opportunity to defend its laws in federal court should not be lightly cut off. The importance of ensuring that States have a fair opportunity to defend their laws in federal court has been recognized by Congress. See 28 U. S. C. §2403(b); Fed. Rule Civ. Proc. 24(a)(1). These provisions—even if not directly applicable in this case because the secretary remained a party—reflect the weighty interest that a State has in protecting its own laws. Respect for state sovereignty must also take into account the authority of a State to structure its executive branch in a way that empowers multiple officials to defend its sovereign interests in federal court. See Virginia House of Delegates v. Bethune-Hill, 587 U. S. ___, ___. The unusual course that this litigation took should not obscure the important constitutional consideration at stake. Pp. 7–9.

   (2) The panel also erred in its evaluation of the other factors that bear on all applications for appellate intervention. The panel’s assessment of the timeliness of the attorney general’s motion to intervene was mistaken. While an important consideration, timeliness depends on the circumstances, and the progression of the litigation is “not solely dispositive.” NAACP v. New York, 413 U. S. 345, 366. Here, the most important circumstance relating to timeliness is that the attorney general sought to intervene “as soon as it became clear” that the Commonwealth’s interests “would no longer be protected” by the parties in the case. United Airlines, Inc. v. McDonald, 432 U. S. 385, 394. Because the attorney general’s need to intervene did not arise until the secretary ceased defending the state law, the timeliness of his motion should be assessed in relation to that point in time. NAACP v. New York, 413 U. S. 345, distinguished. Pp. 10–12.

   (3) The panel’s finding that granting intervention would prejudice respondents was similarly flawed. While the attorney general’s rehearing petition pressed an issue (third-party standing) not raised in the secretary’s appellate briefs, allowing intervention would not have necessitated resolution of that issue. See, e.g., McDonald, 432 U. S., at 394. Moreover, respondents’ loss of its claimed expectations around election of a Governor with a history of declining to defend abortion restrictions is not cognizable as unfair prejudice in the sense relevant here. Pp. 12–13.

831 Fed. Appx. 748, reversed and remanded.

 Alito, J., delivered the opinion of the Court, in which Roberts, C. J., and Thomas, Gorsuch, Kavanaugh, and Barrett, JJ., joined. Thomas, J., filed a concurring opinion. Kagan, J., filed an opinion concurring in the judgment, in which Breyer, J., joined. Sotomayor, J., filed a dissenting opinion.