J. SKELLY WRIGHT, Chief Judge:

This case concerns a request under the Freedom of Information Act (FOIA) by appellant Mark A. Allen that the Central Intelligence Agency (CIA) disclose a 15-page document containing information related to the assassination of President Kennedy. Citing Exemption 2 of the FOIA, the CIA has refused to release portions of the document containing its filing and routing instructions. Other portions of the document have been withheld under Exemptions 1 or 3 of the FOIA. The District Court granted summary judgment in favor of the CIA with respect to all three exemptions. Finding merit in many of the appellant's arguments, we reverse with respect to Exemption 2. And with respect to Exemptions 1 and 3, we vacate and remand for an in camera inspection to determine the applicability of the exemptions.

I. FACTS AND PROCEDURAL BACKGROUND

Mark Allen has for a number of years engaged in extensive research concerning the murder of President Kennedy. On July 24, 1978 he made an FOIA request for a CIA document identified as Item No. 509-803. This document contains CIA-developed information about the activities of Lee Harvey Oswald in Mexico City during the seven-week period prior to the President's assassination. The CIA refused to release the document on the basis of Exemptions 1, 2, and 3 of the FOIA.

On September 18, 1978 Allen initiated this FOIA suit in the District Court, challenging the CIA's withholding of the requested document. In January 1979 the CIA moved to dismiss the suit and supported the motion with the affidavit of CIA Officer Robert E. Owen. The District Court granted the motion. Shortly after Allen had filed a notice of appeal with this court, however, the CIA asked us to remand the case for supplementing of the record. We granted the CIA's motion on October 31, 1979 and remanded the case for proceedings not inconsistent with Founding Church of Scientology v. Bell, 603 F.2d 945 (D.C. Cir. 1979). During the subsequent proceedings the CIA released portions of the requested document and filed a supplemental affidavit of CIA Officer Owen. Meanwhile, Allen made several requests for discovery, all of which were denied by the District Court. On February 6, 1980 the District Court granted summary judgment in favor of the CIA, without having made an in camera inspection of the document. Allen then brought this appeal, challenging the denial of discovery and the grant of summary judgment.

II. THE FILING AND ROUTING INSTRUCTIONS

The CIA withheld those portions of the document containing filing and routing instructions on the basis of Exemption 2 of the FOIA, which exempts from disclosure matters "related solely to the internal personnel rules and practices of an agency." Appellant Allen argues that Exemption 2 does not cover filing and routing instructions. The District Court held the exemption applicable.

We disagree. In Jordan v. U.S. Dep't of Justice, 591 F.2d 753 (D.C. Cir. 1978) ( en banc), this court held "that the phrase `internal personnel' [in Exemption 2] modifies both `rules' and `practices'." Id. at 764. Although it is thus clear that "Congress intended the exemption to be read as a composite clause, covering only internal personnel matters," id. (emphasis added), it is still necessary to examine the exemption's legislative history to ascertain its scope. Unfortunately, the House and Senate reports on the legislation that enacted Exemption 2 differ in the scope they attributed to the exemption. The Senate report stated:

Exemption No. 2 relates only to the internal personnel rules and practices of an agency. Examples of these may be rules as to personnel's use of parking facilities or regulation of lunch hours, statements of policy as to sick leave, and the like.

The House report described the exemption in broader terms:

2. Matters related solely to the internal personnel rules and practices of any agency: Operating rules, guidelines, and manuals of procedure for Government investigators or examiners would be exempt from disclosure, but this exemption would not cover all "matters of internal management" such as employee relations and working conditions and routine administrative procedures which are withheld under the present law.

The Supreme Court addressed the conflict between the two reports in Dep't of Air Force v. Rose, 425 U.S. 352, 96 S.Ct. 1592, 48 L.Ed.2d 11 (1976). The Court held that the Senate report provided a better indication of congressional intent. Id. at 365-367, 96 S.Ct. at 1596-1602. In the instant case there is little doubt that the narrow scope of Exemption 2 reflected in the Senate report does not extend to the filing and routing instructions. That report, by the examples of exempt matters it gives in the portion quoted above, makes clear that the exemption covers nothing more than trivial administrative personnel rules generally concerning hours, pay, and permitted activity while at work. Filing and routing instructions for a document, however, are plainly not included in that narrow category of administrative personnel rules and are totally unlike any of the examples cited. We thus share the view of appellant that the filing and routing instructions are outside the ambit of Exemption 2. The District Court's holding to the contrary is accordingly reversed and the CIA is directed to release those portions of the document containing filing and routing instructions.

III. THE PORTIONS OF THE DOCUMENT WITHHELD UNDER EXEMPTIONS 1 AND 3

The CIA relies on Exemptions 1 and 3 as justification for its withholding of portions of the document other than the filing and routing instructions. Exemption 1 permits withholding of matters that are authorized by Executive Order to be kept secret and "are in fact properly classified pursuant to such Executive order[.]" Exemption 3 permits nondisclosure of information "specifically exempted from disclosure by statute[.]" Allen contends that summary judgment was improper with respect to Exemptions 1 and 3 because the two affidavits presented by the CIA failed to demonstrate that the withheld portions of the document come within the two exemptions. We agree.

A. The Adequacy of the CIA Affidavits

The FOIA directs trial courts to conduct de novo review of the applicability of the particular exemptions cited by the agency to the withheld matters. 5 U.S.C. § 552(a)(4)(B) (1976). To assist the trial court in making its de novo review agencies are expected to submit affidavits demonstrating the applicability of the exemptions. In some cases the agency affidavits will provide a sufficient basis for decision without in camera inspection. In Hayden v. National Security Agency/Central Security Service, 608 F.2d 1381 (D.C. Cir. 1979), cert. denied, 446 U.S. 937, 100 S.Ct. 2156, 64 L.Ed.2d 790 (1980), this court enunciated the standard for granting such summary judgment:

[T]he affidavits must show, with reasonable specificity, why the documents fall within the exemption. The affidavits will not suffice if the agency's claims are conclusory, merely reciting statutory standards, or if they are too vague or sweeping. If the affidavits provide specific information sufficient to place the documents within the exemption category, if this information is not contradicted in the record, and if there is no evidence in the record of agency bad faith, then summary judgment is appropriate without in camera review of the documents. * * *

Id. at 1387 (footnotes omitted).

In the instant case we are of the view that the CIA affidavits were not "reasonabl[y] specific," but rather were "conclusory, merely reciting statutory standards," and that summary judgment was accordingly inappropriate.

1. The Exemption 1 claims

Exemption 1 requires that the most recent classification of a requested document be in conformity with both the procedural and substantive criteria of the then-applicable Executive Order. See Lesar v. U.S. Dep't of Justice, 636 F.2d 472, 483 (D.C. Cir. 1980) ( citing S.Rep. No. 1200, 93d Cong., 2d Sess. 11-12 (1974) U.S. Code Cong. Admin. News 1974, pp. 6267, 6285; Zweibon v. Mitchell, 516 F.2d 594, 642 (D.C. Cir. 1975) ( en banc) ( quoting H.R. Rep. No. 1380, 93d Cong., 2d Sess. 12 (1974) U.S. Code Cong. Admin. News 1974, p. 6267), cert. denied, 425 U.S. 944, 96 S.Ct. 1684, 48 L.Ed.2d 187 (1976). While in the instant case both affidavits of CIA Officer Owen state that the document was properly classified under Executive Order 12065, they are drawn in conclusory terms that merely parrot the language of the Executive Order. There is no basis on which a trial court might conclude that the procedural requirements of Executive Order 12065 have been satisfied. For instance, Section 1-501 of Executive Order 12065 requires that

[a]t the time of original classification, the following shall be shown on the face of paper copies of all classified documents:

(a) the identity of the original classification authority;

(b) the office of origin;

(c) the date or event for declassification or review; and

(d) one of the three classification designations defined in Section 1-1.

The two affidavits in the present case, however, indicate neither the "identity of the original classifi[er]" nor "the date or event for declassification or review."

Owen's affidavits are also defective in that they do not permit a trial court to conclude that the document was classified in conformity with the substantive requirements of Executive Order 12065. Representative of the conclusory nature of the affidavits is that portion of Owen's supplemental affidavit purporting to justify the withholding of almost the entirety of pages 4-9 of the document:

12. Deletions designated with the letters "A B" on pages 4 through 9, in paragraphs 5 through 12, show where portions were deleted to protect against the disclosure of intelligence sources and methods. The substance in these paragraphs concern one sequence of events, which has been the subject of a number of other documents which have been released for public access. The material is presented in such a manner, in this document, that to name the principal figures would result in the eventual identification of the intelligence sources who produced the information and the intelligence methods used in the process. Such a disclosure would compromise the intelligence sources and methods involved, which are currently viable and functioning. The information is thus exempt from release pursuant to FOIA exemptions (b)(1) and (b)(3) * * *.[]

The affidavit's reliance on such expansive phrases as "intelligence sources and methods," "sequence of events," and "process" falls far short of providing the "reasonable specificity" that this court has held is required for summary judgment without in camera inspection. Indeed, the statement does not adequately demonstrate that the substantive standard for classification under Executive Order 12065 has been met. Section 1-302 of that Order states that information "may not be classified unless an original classification authority also determines that its unauthorized disclosure reasonably could be expected to cause at least identifiable damage to the national security." Here, though, the CIA relies on the trial court to draw an inference of "identifiable damage." Unfortunately, the description fails to indicate whether disclosure of this document will hasten the "eventual identification of * * * intelligence methods" that would likely occur even without disclosure of the document.

The affidavits also afford no basis for a conclusion that all "reasonably segregable" nonexempt portions of the document have been released. They do not even contain an assertion to that effect. The CIA argues that by releasing portions of the documents on remand it made clear that no segregable nonexempt portions remain withheld. But release of portions of the document on remand may reflect nothing more than the Agency's attempt to convince the reviewing court of its good faith. To accept the CIA's argument would constitute an abandonment of the trial court's obligation under the FOIA to conduct a de novo review.

2. The Exemption 3 claims

For purposes of its Exemption 3 claims the CIA invokes Sections 403(d)(3) and 403g of Title 50, which exempt from disclosure information that might reveal CIA "intelligence sources and methods." While this court has held that these two statutory provisions are exempting statutes for purposes of Exemption 3, see Goland v. CIA, 607 F.2d 339 (D.C. Cir. 1978), cert. denied, 445 U.S. 927, 100 S.Ct. 1312, 63 L.Ed.2d 759 (1980), we are nevertheless of the view that the District Court erred in granting summary judgment with respect to Exemption 3.

With respect to those portions of the document withheld under Exemption 3, the affidavits fail to demonstrate that the portions are clearly exempt. Indeed, the affidavits of Robert Owen are no less conclusory or nonsupportive with respect to the Exemption 3 claims than they are with respect to the Exemption 1 claims. The CIA's affidavits do little more than parrot the language of Section 403(d)(3) by stating that "intelligence sources and methods" will be compromised if the document is disclosed. But as this court's opinion in Sims v. CIA, (D.C. Cir. No. 79-2203, decided September 29, 1980), demonstrates, the phrase "intelligence sources and methods" is susceptible to varying interpretations, some of which are unacceptably broad. Thus, unless greater specificity is provided regarding the nature of the "intelligence sources and methods," it is impossible for a trial court to conclude that withholding of portions of the document under Exemption 3 was proper.

In addition to the failure of the affidavits to show that the portions withheld under Exemption 3 are clearly exempt, they also fail to indicate whether there is any segregable, nonexempt information still withheld — the same defect that exists with respect to the portions withheld under Exemption 1.

B. In Camera Inspection in FOIA Cases

As the previous section demonstrates, the District Court erred in granting summary judgment in favor of the CIA on Exemptions 1 and 3. While in certain cases it might be appropriate to remand for a taking of further affidavits, in the instant case we are of the view that the District Court should conduct an in camera inspection of the document. To understand why we hold that in camera inspection is required in the instant case, however, we must first look at the terms and legislative history of the FOIA.

1. The legislative history of the 1974 and 1976 Amendments to the FOIA

Underlying the enactment of the FOIA in 1966 was the congressional desire to provide "full agency disclosure unless information is exempted under clearly delineated statutory language[.]" S.Rep. No. 813, 89th Cong., 1st Sess. 3 (1965). The courts were given an especially significant role to play in enforcement of the FOIA. Federal District Courts were granted "jurisdiction to enjoin the agency from the withholding of agency records and to order the production of any agency records improperly withheld from the complainant." In such cases, Congress explicitly provided that "the court shall determine the matter de novo and the burden shall be upon the agency to sustain its action."

Unfortunately, the judiciary was at first reluctant to assume fully the difficult supervisory role that Congress had established for it. In EPA v. Mink, 410 U.S. 73, 93 S.Ct. 827, 35 L.Ed. 119 (1973), the Supreme Court held that District Courts, in reviewing nondisclosure of a document under Exemption 1, could not engage in in camera inspection of the document. Rather, the Court held that reviewing courts were only charged with the responsibility of ensuring the procedural — not substantive — propriety of the classification. In barring in camera inspection for Exemption 1 claims, the Court observed that "Congress chose to follow the Executive's determination in these matters and that choice must be honored." Id. at 81, 93 S.Ct. at 833.

Congress reacted swiftly to the Mink decision. In 1974 it amended the FOIA to provide explicitly that a court engaging in de novo review of agency nondisclosure "may examine the contents of such agency records in camera to determine whether such records or any part thereof shall be withheld under any of the exemptions[.]" Congress also rewrote Exemption 1 so as to make clear that reviewing courts were charged with the responsibility of reviewing de novo the substantive as well as procedural propriety of the classification. The exemption now covers matters that are

(A) specifically authorized under criteria established by an Executive order to be kept secret in the interest of national defense or foreign policy and (B) are in fact properly classified pursuant to such Executive order.[]

The legislative history of the 1974 Amendments to the FOIA demonstrates quite clearly that Congress sought to overrule Mink and facilitate in camera inspection of documents. In 1974 both the House and the Senate took up legislation that amended the Freedom of Information Act. In the House the Committee on Government Operations reported a bill that, among other things, would have amended the FOIA to include the language now in Section 552(a)(3)(B) of the FOIA authorizing courts to conduct in camera inspection. It also would have rewritten Exemption 1 to cover information "authorized under criteria established by an Executive order to be kept secret in the interest of the national defense or foreign policy[.]" The House passed the reported bill with only a technical amendment by a vote of 383 to 8.

In the Senate the Committee on the Judiciary reported a bill with liberal language granting reviewing courts the authority to employ in camera inspection. But bowing to pressure from the President, the Committee proposed restrictive language concerning the judicial role in Exemption 1 claims: agency withholdings of documents were to be sustained unless they were without a "reasonable basis." When the bill reached the Senate floor, however, Senator Muskie introduced an amendment that deleted the restrictive language. After adopting Senator Muskie's amendment, the Senate overwhelmingly passed the amended version of the bill.

The two versions of the 1974 Amendments both went to a Conference Committee. While the Committee was considering the legislation President Ford — who had just succeeded President Nixon — wrote to the Committee expressing his concerns about the proposed legislation. In particular, the President objected that

provisions in both bills * * * would place the burden of proof upon an agency to satisfy a court that a document classified because it concerns military or intelligence * * * secrets and diplomatic relations is, in fact, properly classified, following an in camera inspection of the document by the court. * * *[]

President Ford indicated he could accept in the place of such provisions a provision permitting in camera inspection "only after a review of the evidence did not indicate that the matter had been reasonably classified in the interests of our national security."

The Conference Committee resisted the pressure of the President and instead reported out a bill that, just as the Senate and House versions had, granted reviewing courts broad discretion to employ in camera inspection. With respect to Exemption 1, the Conference Committee merged the Senate and House versions to produce the language now contained in Section 552(b)(1). In its report the Conference Committee made explicit its desire to overrule EPA v. Mink, supra, and authorize reviewing courts to employ in camera inspection under any of the FOIA exemptions:

The conference substitute follows the Senate amendment, providing that in determining de novo whether agency records have been properly withheld, the court may examine records in camera in making its determination under any of the nine categories of exemptions under section 552(b) of the law. In Environmental Protection Agency v. Mink, et al., 410 U.S. 73 [ 93 S.Ct. 827, 35 L.Ed. 119] (1973), the Supreme Court ruled that in camera inspection of documents withheld under section 552(b)(1) of the law, authorizing the withholding of classified information, would ordinarily be precluded in Freedom of Information cases, unless Congress directed otherwise. H.R. 12471 amends the present law to permit such in camera examination at the discretion of the court. While in camera examination need not be automatic, in many situations it will plainly be necessary and appropriate. Before the court orders in camera inspection, the Government should be given the opportunity to establish by means of testimony or detailed affidavits that the documents are clearly exempt from disclosure. The burden remains on the Government under this law.[]

The bill as reported out of Conference Committee was passed overwhelmingly by both houses of Congress. President Ford, however, vetoed the legislation, noting that the concerns he had earlier expressed still remained. Rejecting the objections of the President, Congress overrode the presidential veto.

In sum, the 1974 Amendments to the Freedom of Information Act manifest an unmistakable congressional intent to bolster the authority of reviewing courts. The active role that Congress intended the judiciary to play in enforcing the FOIA was emphasized further by amendments in 1976 that were enacted to overrule the Supreme Court decision in FAA Administrator v. Robertson, 422 U.S. 255, 95 S.Ct. 2140, 45 L.Ed.2d 164 (1975). The case involved Exemption 3 of the FOIA, which at the time covered matters "specifically exempted from disclosure by statute." In Robertson the Court held that this language comprehended a statute that granted a "broad degree of discretion on what information is to be protected[.]" Id. at 266, 95 S.Ct. at 2147. Within 15 months Congress overruled the decision by narrowing Exemption 3 to its present form. The "unmistakable thrust" of the amendment was "to assure that basic policy decisions on governmental secrecy be made by the Legislative rather than the Executive branch." American Jewish Congress v. Kreps, 574 F.2d 624, 628 (D.C. Cir. 1978) (footnote omitted). The Robertson amendment, like the 1974 Amendments, thus evinced a congressional intent that the de novo review mandated by the Freedom of Information Act be extremely thorough so as "to insure that agencies do not impermissibly expand by unreviewed interpretations the `particular types of matters' Congress has exempted from disclosure." Ray v. Turner, 587 F.2d 1187, 1221 (D.C. Cir. 1978) (Wright, C. J., concurring).

The judicial reluctance to assume an active role in reviewing FOIA claims is reflected in both the Mink and Robertson decisions. In response Congress has plainly attempted to strengthen the de novo review that courts must engage in. While Congress has not mandated in camera inspection for any particular subset of FOIA cases, it has nevertheless made clear — by the concern reflected in the 1974 and 1976 Amendments for a thorough and meaningful de novo review — that in certain cases such in camera inspection "will plainly be necessary and appropriate." H.R. Rep. No. 93-1380, 93d Cong., 2d Sess. 8, U.S. Code Cong. Admin. News 1974, p. 6267, reprinted in Source Book at 226. Congress, however, never isolated those instances in which in camera inspection of the requested document is "plainly * * * necessary." While we in no way mean to minimize the broad discretion granted to trial courts over whether to conduct in camera inspection, we think it appropriate in this case to outline some of the considerations that trial courts should take into account in exercising that discretion.

2. Considerations supporting in camera inspection a. Judicial economy

In conducting its de novo review, a trial court should first offer the agency the opportunity to demonstrate, through detailed affidavits and oral testimony, that the withheld information is clearly exempt and contains no segregable, nonexempt portions. See EPA v. Mink, supra, 410 U.S. at 73, 93 S.Ct. at 829. Where the agency fails to meet that burden, a not uncommon event, the court may employ a host of procedures that will provide it with sufficient information to make its de novo determination, including in camera inspection, further agency affidavits, and discovery by the plaintiff.

Courts have been reluctant, however, to conduct in camera inspection, favoring instead the other options available. Where the examination of the requested documents requires herculean labors because of their volume, the reluctance to conduct such inspection is understandable. But when the requested documents are few in number and of short length, such reluctance frequently exacts a cost from the parties and the courts in time and money. An examination of the documents themselves in those instances will typically involve far less time than would be expended in presentation and evaluation of further evidence. The other procedures are usually nothing more than surrogates for in camera inspection. And, when utilization of these surrogates has not proven fruitful, the court not infrequently finds it necessary to conduct in camera inspection — often by direction of an appellate court after a costly appeal has been pursued by the plaintiff.

b. The conclusory nature of the agency affidavits

Where the agency affidavits merely parrot the language of the statute and are drawn in conclusory terms, the court's responsibility to conduct de novo review is frustrated. Sufficiently detailed justifications for the agency's withholding is often impossible, however, because such justifications would reveal the very information sought to be protected. In those instances, we doubt that there is any way the agency action could be sustained without in camera inspection. And in camera inspection permits the courts in such instances to fulfill their statutory obligation to conduct a meaningful de novo review.

c. Bad faith on the part of the agency

Where there is evidence of bad faith on the part of the agency, the representations of the agency lose all trustworthiness. In camera inspection in such situations is "plainly necessary" unless it is clear to the court that the withholding by the agency would not even be sustainable after in camera inspection.

d. Disputes concerning the contents of the document

In camera inspection is most helpful when the dispute over the applicability of the particular exemption centers on the actual contents of the document. On the other hand, such inspection is not appropriate when there is no dispute between the parties as to the document's contents. Interpretation of the scope of an exemption, for instance, is not made any easier by the use of in camera inspection.

e. The agency proposes in camera inspection

The reluctance of the courts to conduct in camera inspection is often attributable to the concern that such inspection will involve judicial intrusion into the activities of the Executive Branch through examination of information it refuses to disclose to the public. But little basis for such concern exists when the agency itself proposes that the court conduct an in camera inspection of the document. In such instances, therefore, use of in camera inspection is more appropriate than in cases where the agency expresses its opposition to the technique.

f. Strong public interest in disclosure

In cases that involve a strong public interest in disclosure there is also a greater call for in camera inspection. The Freedom of Information Act was aimed at ending secret law and insuring that this country have "an informed, intelligent electorate[.]" H.R. Rep. No. 1497, 89th Cong., 2d Sess. 12 (1966) U.S. Code Cong. Admin. News 1966, p. 2419. When citizens request information to ascertain whether a particular agency is properly serving its public function, the agency often deems it in its best interest to stifle or inhibit the probes. It is in these instances that the judiciary plays an important role in reviewing the agency's withholding of information. But since it is in these instances that the representations of the agency are most likely to be protective and perhaps less than accurate, the need for in camera inspection is greater.

C. The Need for In Camera Inspection in the Instant Case

In the instant case, an application of the foregoing considerations convinces us that in camera inspection of the requested document is "plainly necessary" to determine the applicability of Exemptions 1 and 3. First, as is evident from the fact that this is the second appeal to this court, much time and money have been expended by the courts and the parties in determining the applicability of the cited exemptions to the withheld document. What is so startling, however, is that in this case the document itself is only 15 pages in length. The two affidavits by the CIA, on the other hand, total 14 pages, without even counting the attachments. If ever there was a case in which in camera inspection offered the most efficient technique for conducting de novo review, this is it.

Second, the basis on which the CIA refuses to release the undisclosed portions of the document makes de novo review almost impossible without in camera inspection. The CIA concedes that most of the document has been released in other public documents, but argues that its manner of presentation will reveal new information. The CIA thus argues that to require greater specificity in its affidavits would result in disclosure of the information sought to be protected. The only way to escape this dilemma involves use of in camera inspection.

Third, with respect to both the Exemption 1 and the Exemption 3 claims, the contents of the requested documents are in dispute. An examination of the document would make totally unnecessary speculation and inference as to the contents of the document, and firmly resolve the competing assertions made by both sides.

Fourth, the CIA has expressed its willingness for the court to conduct an in camera inspection of the document. It is the plaintiff who resists such inspection in the instant case.

Finally, the plaintiff's request for the document seems in part to be motivated by a desire to determine whether the CIA has frustrated the investigation into or had a role in the assassination of President Kennedy — an event in which the public has demonstrated almost unending interest. Such an FOIA request, in an area of great public interest and that seeks to demonstrate the impropriety of the Agency's actions, makes in camera inspection especially appropriate.

IV. CONCLUSION

For the reasons herein stated, we reverse that portion of the judgment of the District Court holding Exemption 2 applicable to the filing and routing instructions contained in the document. Further, we vacate that portion of the judgment holding Exemptions 1 and 3 applicable to the other portions of the document, and remand for an in camera inspection to determine the applicability of the two exemptions.

Reversed in part, vacated in part, and remanded.

* * * * * *

(3) specifically exempted from disclosure by statute (other than section 552b of this title), provided that such statute (A) requires that the matters be withheld from the public in such a manner as to leave no discretion on the issue, or (B) establishes particular criteria for withholding or refers to particular types of matters to be withheld[.]