Opinion by Judge SCHWARZER; Dissent by Judge MICHAEL DALY HAWKINS.
SCHWARZER, Senior District Judge:The question before us is whether documents submitted by Indian Tribes at the request of the Department of the Interior in the course of consultation over ongoing administrative and adjudicative proceedings involving water rights and allocations affecting the Tribes’ interests are exempt under the Freedom of Information Act as “inter-agency or intra-agency memorandums or letters-” 5 U.S.C. § 552(b)(5) (1994).
FACTUAL BACKGROUND
Klamath Water Users Protective Association (the “Association”) brought this action under the Freedom of Information Act (“FOIA”), 5 U.S.C. § 552, against the Department of the Interior (the “Department”) and its constituent agency, the Bureau of Indian Affairs (“BIA”), see 25 U.S.C. § 1. The Association is a nonprofit association of water users in the Klamath River Basin who receive water from the Klamath Project (the “Project”), a federal reclamation project administered by the Bureau of Reclamation (“Reclamation”), an agency within the Department. See 43 U.S.C. § 1457 (1994). Members of the Association, most of which are public agencies, such as irrigation districts holding contracts with Reclamation, receive water from the Project, as do the Klamath Basin Tribes. Those Tribes include the Klamath Tribes, with fisheries located near Upper Klamath Lake, and the Yurok, Hoopa Valley, and Karuk Tribes, with fisheries on the Klamath River. The former Tribes have demanded that the Department maintain high lake levels to protect their fisheries, while the latter Tribes have demanded increased releases to the Klamath River to benefit their downstream fisheries. The Tribes’ demands, if satisfied, would lead to reduced water allocations to members of the Association and have been protested by Association members who fear water shortages and economic injury in dry years.
In 1995, Reclamation announced its intention to prepare a plan for long-term operation of the Project, the Klamath Project Operation Plan (“KPOP”). The purpose was to enable the Project to operate in conformity with the Department’s vari*1036ous legal obligations in wet as well as dry-years. The Department hired a consulting firm and held a series of meetings with interested parties. The meetings disclosed substantial disagreements among irrigation interests and the Tribes, leading the irrigation interests to fear that their water allocations would be cut. Although a draft KPOP was to be prepared for public comment in 1996, none has so far been released.
In connection with the development of the KPOP, the Department entered into an agreement with the Klamath Basin Tribes to provide consultation and cooperation to assist it in fulfilling its trust obligations. In a separate matter, the Department also filed claims on behalf of the Klamath Tribes in a water rights adjudication process established by the State of Oregon. This adjudication will quantify water rights, including those of the Kla-math Tribes, in the Klamath River Basin.
The Association made several FOIA requests of the BIA for documents provided to or received from the Klamath Basin Tribes pertaining to water resources issues in the Klamath River Basin in order to discern what information was being exchanged during the preparation of the draft KPOP outside the public process. The Department released some documents, but withheld others. After the filing of this action, more were from time to time released and the Association withdrew its request for others. In the end only seven documents remained in dispute. They are listed in the Vaughn index submitted by the Department and are described as memoranda provided by the tribes to the Department for use in the development of the KPOP, a memorandum from the Department concerning the government’s trust obligations in developing the KPOP, and memoranda from the tribes to the Department addressing claims in the water rights adjudication.
The district court granted the Department’s motion for summary judgment. Insofar as relevant to our disposition, the district court held that the documents “qualif[ied] as inter-agency or intra-agency documents under the ‘functional test,’ ” citing Formaldehyde Inst. v. Department of Health and Human Servs., 889 F.2d 1118 (D.C.Cir.1989). It found that the documents “played a role in the agency’s deliberations with regard to the current water rights adjudication and/or the anticipated Plan of Operations. Most of the documents were provided to the agency by the Tribes at the agency’s request.” The district court distinguished Madison County v. Department of Justice, 641 F.2d 1036 (1st Cir.1981), on the ground that “the Tribes are not in current litigation with the government, but instead acted in the role of consultants” and that “[t]he government used all these documents in fulfilling their trust obligation, and as part of their decision making process.” The Association appeals from the judgment. We have jurisdiction of this appeal under 28 U.S.C. § 1291 and reverse.
I. STANDARD OF REVIEW
Ordinarily, review of summary judgment is de novo. In FOIA cases, however, because of their unique nature, we have adopted a two-step standard of review. We first determine whether the district court had an adequate factual basis upon which to base its decision. If so, we review the district court’s conclusion of an exemption’s applicability de novo. See Minier v. CIA, 88 F.3d 796, 800 (9th Cir.1996). Some of our cases have applied the clearly erroneous standard to review of a district court’s final determination of whether a particular document is exempt under the FOIA. See, e.g., Rosenfeld v. United States Dep’t of Justice, 57 F.3d 803, 807 (9th Cir.1995); Frazee v. United States Forest Serv., 97 F.3d 367, 370 (9th Cir.1996); Maricopa Audubon Soc’y v. United States Forest Serv., 108 F.3d 1082, 1085 (9th Cir.1997). As we explained in Schiffer v. FBI, 78 F.3d 1405, 1409 (9th Cir.1996), application of that standard is appropriate in the common FOIA case where the district court’s findings of fact effectively determine the legal conclusion. *1037We recognized, however, that where the adequacy of the factual basis is not disputed, the district court’s legal conclusion whether the FOIA exempts a document from disclosure is reviewed de novo. See id. This appeal raises no factual issues. The question presented, whether the fiduciary and consultant relationship between the Department and the Tribes qualifies the disputed documents under the FOIA’s threshold inter/intra agency test, is one of law. Accordingly, our review is de novo.
II. APPLICATION OF THE FOIA
The FOIA “does not apply to matters that are—
(5) 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. ...”
§ 522(b)(5). We must apply this exemption consistently with our holdings that the FOIA “ ‘mandates a policy of broad disclosure of government documents.’ ” Maricopa, 108 F.3d at 1085 (quoting Church of Scientology v. Department of the Army, 611 F.2d 738, 741 (9th Cir.1980)). When a request is made, an agency may withhold a document only if it falls within one of the nine statutory exemptions in § 522(b) and these exemptions “ ‘must be narrowly construed’ in light of the FOIA’s ‘dominant objective’ of ‘disclosure, not secrecy.’ ” Id. (quoting Department of the Air Force v. Rose, 425 U.S. 352, 361, 96 S.Ct. 1592, 48 L.Ed.2d 11 (1976)). “FOIA imposes on agencies the burden of proving that withheld materials are exempt from disclosure.” Id.
The Department contends that the documents at issue, involving communications between the Tribes and the Department concerning the development of the KPOP and the Oregon water rights adjudication, meet the “functional test” of Exemption 5 for inter-agency/intra-agency communications. It rests its contention on the fact that to fulfill its fiduciary responsibility to protect and manage the natural resources of the Indian Tribes, it entered into a Memorandum of Agreement with the Tribes acknowledging their consultative role in these two matters.
The Department places principal reliance on Formaldehyde Inst. v. Department of Health and Human Servs., 889 F.2d 1118 (D.C.Cir.1989). That case involved the application of Exemption 5 to a peer review letter received by the Centers for Disease Control (“CDC”), an agency within the Department of Health and Human Services, from a professional journal. The journal had reviewed a report submitted by an agency employee, determined not to publish the report, and then forwarded the peer review letter to the agency. The Formaldehyde Institute requested copies of all records of agency contacts with the journal relating to publication or rejection of the report. The agency rejected the request, relying principally on Exemption 5. The court of appeals reversed judgment for the Institute. Its opinion is largely devoted to determining that the peer review letter was predeci-sional and part of the deliberative process. But it also held that the peer review letter qualified under the inter-agency/intra-agency test. Quoting from its prior decision in CNA Fin. Corp. v. Donovan, 830 F.2d 1132, 1161-62 (D.C.Cir.1987), which, in turn, relied on Ryan v. Department of Justice, 617 F.2d 781 (D.C.Cir.1980), it held that “ ‘[wjhether the author is a regular agency employee or a temporary consultant is irrelevant; the pertinent element is the role, if any, that the document plays in the process of agency deliberations.’ ” See Formaldehyde, 889 F.2d at 1118. In Ryan, the court had said that “[w]hen an agency record is submitted by outside consultants as part of the deliberative process, and it was solicited by the agency, we find it entirely reasonable to deem the resulting document to be an ‘intra-agency’ memorandum for purposes of determining the applicability of Exemption 5.” Ryan, 617 F.2d at 790. More recently, the court held that communications mandated by statute between the National Archives and former *1038Presidents relating to access to their presidential records are within Exemption 5. Public Citizen, Inc. v. Department of Justice, 111 F.3d 168, 170-71 (D.C.Cir.1997).
This court has not yet had occasion to address the reach of the inter-agency/in-tra-agency test under Exemption 5 and to determine whether the expansive interpretation adopted by the District of Columbia Circuit is consistent with the policy of broad disclosure on which the FOIA is anchored. We need not reach the issue here because this case differs in a material respect from those on which the Department relies. Here, the Tribes with whom the Department has a consulting relationship have a direct interest in the subject matter of the consultations. The development of the KPOP and the Oregon water rights adjudication will affect water allocations to the Tribes as well as those to members of the Association. While the Tribes and the Association may not be engaged in conventional adversary litigation, they assert conflicting claims in a contentious proceeding involving the Department. The documents at issue are relevant to those claims. Thus, this case differs from Public Citizen, Inc. v. Department of Justice, on which the Department relies, in that it presents not simply “the potential for an adversary relationship” but a clear and present conflict with respect to the subject matter of the documents, which is for the Department to resolve. See 111 F.3d at 171 (“At some point, of course, features of the other relationships (above all, a possible future adversary one) might come to eclipse the consultative relationship.... ”).
We have held that documents submitted to an agency by persons outside the government as part of an administrative proceeding are not internal agency documents exempt from disclosure. See Van Bourg, Allen, Weinberg & Roger v. NLRB, 751 F.2d 982, 984-85 (9th Cir.1985) (affidavits describing union practices, officials and members submitted as part of an NLRB unfair labor practice investigation not within Exemption 5). The Department distinguishes the instant case on the ground that it had requested the advice of the Tribes. But that distinction makes no difference because, as County of Madison v. United States Dep’t of Justice, 641 F.2d 1036, 1040 (1st Cir.1981), holds in a similar context, consultation with the tribes is not similar to ‘“the advice from staff assistants and exchange of ideas among agency personnel’ that forms the object of exemption five,” which exemption is limited to “interagency or intra-agency memorandums or letters.” In County of Madison, the court held that communications between an Indian tribe and the Department of Justice in an unsuccessful effort to settle litigation between them did not qualify as inter-agency/intra-agency documents. It distinguished cases such as Ryan from the case before it in which, “by contrast, the Oneidas approached the government with their own interest in mind. While they came to parley, they were past and potential adversaries, not coopted colleagues.” Id. While it is true that the Department requested the advice of the Tribes, the matters with respect to which it sought advice were matters in which the Tribes had their own interest and the communications presumptively served that interest, even if they incidentally benefited the Department. Thus, we conclude that even were we to take an expansive view of the inter-agency/intra-agency test, these documents do not qualify for exemption.
To hold otherwise would extend Exemption 5 to shield what amount to ex parte communications in contested proceedings between the Tribes and the Department. Rejection of such an extension does not conflict with the Department’s fiduciary obligations to the Tribes. See United States v. Cherokee Nation, 480 U.S. 700, 707, 107 S.Ct. 1487, 94 L.Ed.2d 704 (1987). The Department exercises its regulatory powers in the context of the governing statutes; while it must act in the interests of the tribes, it may not afford them greater rights than they would have under the regulatory scheme. See Skokomish Indian Tribe v. Federal Ener*1039gy Regulatory Comm’n, 121 F.3d 1303, 1308 (9th Cir.1997). Indeed, the 1994 Presidential Memorandum directing the heads of all executive departments and agencies to consult with tribal governments prior to taking actions that affect them specifically, provides that “[a]ll such consultations are to be open and candid so that all interested parties may evaluate for themselves the potential impact of relevant proposals.” 3 C.F.R. 1007 (1995). And a corresponding directive issued by the Secretary of the Interior in 1993 contains the identical mandate. See United States Dept, of the Interior, Protection of Indian Trust Resource Procedures app. Order No. 3175 (1993).
Because the documents fail to meet the threshold inter-agency/intra-agency test, we need not reach the other issues raised by the Association. The judgment is REVERSED.
REVERSED.