Justice Souter, delivered the opinion of the Court.
Documents in issue here, passing between Indian Tribes and the Department of the Interior, addressed tribal interests subject to state and federal proceedings to determine water allocations. The question is whether the documents are exempt from the disclosure requirements of the Freedom of Information Act, as "intra-agency memorandums or
Two separate proceedings give rise to this case, the first a planning effort within the Department of the Interior's Bureau of Reclamation, and the second a state water rights adjudication in the Oregon courts. Within the Department of the Interior, the Bureau of Reclamation (Reclamation) administers the Klamath Irrigation Project (Klamath Project or Project), which uses water from the Klamath River Basin to irrigate territory in Klamath County, Oregon, and two northern California counties. In 1995, the Department began work to develop a long-term operations plan for the Project, to be known as the Klamath Project Operation Plan (Plan), which would provide for allocation of water among competing uses and competing water users. The Department asked the Klamath as well as the Hoopa Valley, Karuk, and Yurok Tribes (Basin Tribes) to consult with Reclamation on the matter, and a memorandum of understanding between the Department and the Tribes recognized that "[t]he United States Government has a unique legal relationship with Native American tribal governments," and called for "[a]ssessment, in consultation with the Tribes, of the impacts of the [Plan] on Tribal trust resources." App. 59, 61.
During roughly the same period, the Department's Bureau of Indian Affairs (Bureau) filed claims on behalf of the Klamath Tribe alone in an Oregon state-court adjudication intended to allocate water rights. Since the Bureau is responsible for administering land and water held in trust for Indian tribes, 25 U. S. C. § 1a; 25 CFR subch. H, pts. 150-181 (2000), it consulted with the Klamath Tribe, and the two exchanged written memorandums on the appropriate scope of the claims ultimately submitted by the United States for the benefit of the Klamath Tribe. The Bureau does not, however,
Respondent, the Klamath Water Users Protective Association (Association), is a nonprofit association of water users in the Klamath River Basin, most of whom receive water from the Klamath Project, and whose interests are adverse to the tribal interests owing to scarcity of water. The Association filed a series of requests with the Bureau under the Freedom of Information Act (FOIA), 5 U. S. C. § 552, seeking access to communications between the Bureau and the Basin Tribes during the relevant time period. The Bureau turned over several documents but withheld others as exempt under the attorney work-product and deliberative process privileges. These privileges are said to be incorporated in FOIA Exemption 5, which exempts from disclosure "inter-agency or intra-agency memorandums or letters which would not be available by law to a party other than an agency in litigation with the agency." § 552(b)(5). The Association then sued the Bureau under FOIA to compel release of the documents.
By the time of the District Court ruling, seven documents remained in dispute, three of them addressing the Plan, three concerned with the Oregon adjudication, and the seventh relevant to both proceedings. See 189 F.3d 1034, 1036 (CA9 1999), App. to Pet. for Cert. 41a-49a. Six of the documents were prepared by the Klamath Tribe or its representative and were submitted at the Government's behest to the Bureau or to the Department's Regional Solicitor; a Bureau official prepared the seventh document and gave it to lawyers for the Klamath and Yurok Tribes. See ibid.
The Court of Appeals for the Ninth Circuit reversed. 189 F.3d 1034 (1999). It recognized that some Circuits had adopted a "functional" approach to Exemption 5, under which a document generated outside the Government might still qualify as an "intra-agency" communication. See id., at 1037-1038. The court saw no reason to go into that, however, for it ruled out any application of Exemption 5 on the ground that "the Tribes with whom the Department has a consulting relationship have a direct interest in the subject matter of the consultations." Id., at 1038. The court said that "[t]o hold otherwise would extend Exemption 5 to shield what amount to ex parte communications in contested proceedings between the Tribes and the Department." Ibid. Judge Hawkins dissented, for he saw the documents as springing "from a relationship that remains consultative rather than adversarial, a relationship in which the Bureau and Department were seeking the expertise of the Tribes, rather than opposing them." Id., at 1045. He saw the proper enquiry as going not to a document's source, but to the role it plays in agency decisionmaking. See id., at 1039. We granted certiorari in view of the decision's significant impact on the relationship between Indian tribes and the Government, 530 U.S. 1304 (2000), and now affirm.
Upon request, FOIA mandates disclosure of records held by a federal agency, see 5 U. S. C. § 552, unless the documents fall within enumerated exemptions, see § 552(b). "[T]hese
Exemption 5 protects from disclosure "inter-agency or intra-agency memorandums or letters which would not be available by law to a party other than an agency in litigation with the agency." 5 U. S. C. § 552(b)(5). To qualify, a document must thus satisfy two conditions: its source must be a Government agency, and it must fall within the ambit of a privilege against discovery under judicial standards that would govern litigation against the agency that holds it.
Our prior cases on Exemption 5 have addressed the second condition, incorporating civil discovery privileges. See, e. g., United States v. Weber Aircraft Corp., 465 U.S. 792, 799-800 (1984); NLRB v. Sears, Roebuck & Co., 421 U.S. 132, 148 (1975) ("Exemption 5 withholds from a member of the public documents which a private party could not discover in litigation with the agency"). So far as they might matter here, those privileges include the privilege for attorney workproduct and what is sometimes called the "deliberative process" privilege. Work product protects "mental processes of the attorney," United States v. Nobles, 422 U.S. 225, 238 (1975), while deliberative process covers "documents reflecting advisory opinions, recommendations and deliberations comprising part of a process by which governmental decisions and policies are formulated," Sears, Roebuck & Co., 421 U. S., at 150 (internal quotation marks omitted). The deliberative process privilege rests on the obvious realization that officials will not communicate candidly among themselves
The point is not to protect Government secrecy pure and simple, however, and the first condition of Exemption 5 is no less important than the second; the communication must be "inter-agency or intra-agency." 5 U. S. C. § 552(b)(5). Statutory definitions underscore the apparent plainness of this text. With exceptions not relevant here, "agency" means "each authority of the Government of the United States," § 551(1), and "includes any executive department, military department, Government corporation, Government controlled corporation, or other establishment in the executive branch of the Government . . . , or any independent regulatory agency," § 552(f).
Although neither the terms of the exemption nor the statutory definitions say anything about communications with outsiders, some Courts of Appeals have held that in some circumstances a document prepared outside the Government may nevertheless qualify as an "intra-agency" memorandum under Exemption 5. See, e. g., Hoover v. Dept. of Interior, 611 F.2d 1132, 1137-1138 (CA5 1980); Lead Industries Assn. v. OSHA, 610 F.2d 70, 83 (CA2 1979); Soucie v. David, 448 F.2d 1067 (CADC 1971). In Department of Justice v. Julian, 486 U.S. 1 (1988), Justice Scalia, joined by Justices O'Connor and White, explained that "the most natural meaning of the phrase `intra-agency memorandum' is a memorandum that is addressed both to and from employees of a single agency," id., at 18, n. 1 (dissenting opinion). But his opinion also acknowledged the more expansive reading by some Courts of Appeals:
Typically, courts taking the latter view have held that the exemption extends to communications between Government agencies and outside consultants hired by them. See, e. g., Hoover, supra, at 1138 ("In determining value, the government may deem it necessary to seek the objective opinion of outside experts rather than rely solely on the opinions of government appraisers"); Lead Industries Assn., supra, at 83 (applying Exemption 5 to cover draft reports "prepared by outside consultants who had testified on behalf of the agency rather than agency staff"); see also Government Land Bank v. GSA, 671 F.2d 663, 665 (CA5 1982) ("Both parties agree that a property appraisal, performed under contract by an independent professional, is an `intra-agency' document for purposes of the exemption"). In such cases, the records submitted by outside consultants played essentially the same part in an agency's process of deliberation as documents prepared by agency personnel might have done. To be sure, the consultants in these cases were independent contractors and were not assumed to be subject to the degree of control that agency employment could have entailed; nor do we read the cases as necessarily assuming that an outside consultant must be devoid of a definite point of view when the agency contracts for its services. But the fact
The Department purports to rely on this consultant corollary to Exemption 5 in arguing for its application to the Tribe's communications to the Bureau in its capacity of fiduciary for the benefit of the Indian Tribes. The existence of a trust obligation is not, of course, in question, see United States v. Cherokee Nation of Okla., 480 U.S. 700, 707 (1987); United States v. Mitchell, 463 U.S. 206, 225 (1983); Seminole Nation v. United States, 316 U.S. 286, 296-297 (1942). The fiduciary relationship has been described as "one of the primary cornerstones of Indian law," F. Cohen, Handbook of Federal Indian Law 221 (1982), and has been compared to one existing under a common law trust, with the United States as trustee, the Indian tribes or individuals as beneficiaries, and the property and natural resources managed by the United States as the trust corpus. See, e. g., Mitchell, supra, at 225. Nor is there any doubt about the plausibility of the Government's assertion that the candor of tribal communications with the Bureau would be eroded without the protections of the deliberative process privilege recognized under Exemption 5. The Department is surely right in saying that confidentiality in communications with tribes is conducive to a proper discharge of its trust obligation.
From the recognition of this interest in frank communication, which the deliberative process privilege might protect, the Department would have us infer a sufficient justification for applying Exemption 5 to communications with the Tribes, in the same fashion that Courts of Appeals have found sufficient reason to favor a consultant's advice that
There is, however, no textual justification for draining the first condition of independent vitality, and once the intraagency condition is applied,
The Department insists that the Klamath Tribe's consultant-like character is clearer in the circumstances of the Oregon adjudication, since the Department merely represents the interests of the Tribe before a state court that will
But, again, the dispositive point is that the apparent object of the Tribe's communications is a decision by an agency of the Government to support a claim by the Tribe that is necessarily adverse to the interests of competitors. Since there is not enough water to satisfy everyone, the Government's position on behalf of the Tribe is potentially adverse to other users, and it might ask for more or less on behalf of the Tribe depending on how it evaluated the tribal claim compared with the claims of its rivals. The ultimately adversarial character of tribal submissions to the Bureau therefore seems the only fair inference, as confirmed by the Department's acknowledgment that its "obligation to represent the Klamath Tribe necessarily coexists with the duty to protect other federal interests, including in particular its interests with respect to the Klamath Project." Reply Brief for Petitioners 8; cf. Nevada v. United States, 463 U.S. 110, 142 (1983) ("[W]here Congress has imposed upon the United States, in addition to its duty to represent Indian tribes, a duty to obtain water rights for reclamation projects, and has even authorized the inclusion of reservation lands within a project, the analogy of a faithless private fiduciary cannot be
Quite apart from its attempt to draw a direct analogy between tribes and conventional consultants, the Department argues that compelled release of the documents would itself impair the Department's performance of a specific fiduciary obligation to protect the confidentiality of communications with tribes.
All of this boils down to requesting that we read an "Indian trust" exemption into the statute, a reading that is out
The judgment of the Court of Appeals is affirmed.
It is so ordered.
Lucy A. Dalglish, Gregg P. Leslie, and Bruce W. Sandford filed a brief for the Reporters Committee for Freedom of the Press et al.as amici curiae urging affirmance.
Briefs of amici curiae were filed for the City of Tacoma, Washington, by J. Richard Creatura; and for United South and Eastern Tribes, Inc., by William W. Taylor III, Michael R. Smith, and Eleanor H. Smith.