Stat. 251. In 1974, this exemption was rewritten to permit the nondisclosure of "investigatory records compiled for law enforcement purposes," but only to the extent that producing such records would involve one of six specified dangers. The first of these, with which we are here concerned, is that production of the records would "interfere with enforcement proceedings."

The Board contends that the original language of Exemption 7 was expressly designed to protect existing NLRB policy forbidding disclosure of statements of prospective witnesses until after they had testified at unfair labor practice hearings. In its view, the 1974 amendments preserved Congress' original intent to protect witness statements in unfair labor practice proceedings from premature disclosure, and were directed primarily at case law that had applied Exemption 7 too broadly to cover any material, regardless of its nature, in an investigatory file compiled for law enforcement purposes. The Board urges that a particularized, case-bycase showing is neither required nor practical, and that witness statements in pending unfair labor practice proceedings are exempt as a matter of law from disclosure while the hearing is pending.

Respondent disagrees with the Board's analysis of the 1974 amendments. It argues that the legislative history conclusively demonstrates that the determination of whether disclosure of any material would "interfere with enforcement proceedings" must be made on an individual, case-by-case basis. While respondent agrees that the statements sought

reports prepared by, on behalf of, or for the use of an agency responsible for the regulation or supervision of financial institutions; or

"(9) geological and geophysical information and data, including maps, concerning wells.

"Any reasonably segregable portion of a record shall be provided to any person requesting such record after deletion of the portions which are exempt under this subsection."

here are "investigatory files compiled for law enforcement purposes," and that they are related to an imminent enforcement proceeding, it argues that the Board's failure to make a specific factual showing that their release would interfere with this proceeding defeats the Board's Exemption 7 claim.

A

The starting point of our analysis is with the language and structure of the statute. We can find little support in the language of the statute itself for respondent's view that determinations of "interference" under Exemption 7 (A) can be made only on a case-by-case basis. Indeed, the literal language of Exemption 7 as a whole tends to suggest that the contrary is true. The Exemption applies to:

"investigatory records compiled for law enforcement purposes, but only to the extent that the production of such records would (A) interfere with enforcement proceedings, (B) deprive a person of a right to a fair trial or an impartial adjudication, (C) constitute an unwarranted invasion of personal privacy, (D) disclose the identity of a confidential source and, in the case of a record compiled by a criminal law enforcement authority in the course of a criminal investigation, or by an agency conducting a lawful national security intelligence investigation, confidential information furnished only by the confidential source, (E) disclose investigative techniques and procedures, or (F) endanger the life or physical safety of law enforcement personnel."

There is a readily apparent difference between subdivision (A) and subdivisions (B), (C), and (D). The latter subdivisions refer to particular cases-"a person," "an unwarranted invasion," "a confidential source"-and thus seem to require a showing that the factors made relevant by the statute are present in each distinct situation. By contrast, since subdivision (A) speaks in the plural voice about "enforcement

proceedings," it appears to contemplate that certain generic determinations might be made.

Respondent points to other provisions of FOIA in support of its interpretation. It suggests that, because FOIA expressly provides for disclosure of segregable portions of records and for in camera review of documents, and because the statute places the burden of justifying nondisclosure on the Government, 5 U. S. C. §§ 552 (a) (4) (B), (b) (1976 ed.), the Act necessarily contemplates that the Board must specifically demonstrate in each case that disclosure of the particular witness' statement would interfere with a pending enforcement proceeding. We cannot agree. The in camera review provision is discretionary by its terms, and is designed to be invoked when the issue before the District Court could not be otherwise resolved; it thus does not mandate that the documents be individually examined in every case. Similarly, although the segregability provision requires that nonexempt portions of documents be released, it does not speak to the prior question of what material is exempt. Finally, the mere fact that the burden is on the Government to justify nondisclosure does not, in our view, aid the inquiry as to what kind of burden the Government bears.

We thus agree with the parties that resolution of the question cannot be achieved through resort to the language of the statute alone. Accordingly, we now turn to an examination of the legislative history.

B

In originally enacting Exemption 7, Congress recognized that law enforcement agencies had legitimate needs to keep certain records confidential, lest the agencies be hindered in their investigations or placed at a disadvantage when it came time to present their cases. Foremost among the purposes of this Exemption was to prevent "harm [to] the Government's case in court," S. Rep. No. 813, 89th Cong., 1st Sess. (1965), reprinted in Freedom of Information Act Source Book, Sub

committee on Administrative Practice & Procedure, Senate Judiciary Committee, S. Doc. No. 93–82, p. 44 (1974) (hereinafter cited as 1974 Source Book), by not allowing litigants "earlier or greater access" to agency investigatory files than they would otherwise have,. H. R. Rep. No. 1497, 89th Cong., 2d Sess. (1966), reprinted in 1974 Source Book 32. Indeed, in an unusual, post-passage reconsideration vote, the Senate modified the language of this Exemption specifically to meet Senator Humphrey's concern that it might be construed to require disclosure of "statements of agency witnesses" prior to the time they were called on to testify in agency proceedings. Id., at 110.

Senator Humphrey was particularly concerned that the initial version of the Exemption passed by the Senate might be "susceptible to the interpretation that once a complaint of unfair labor practice is filed by the General Counsel of the NLRB, access could be had to the statements of all witnesses, whether or not these statements are relied upon to support the complaint." Ibid. He argued against this, noting that "[w]itnesses would be loath to give statements if they knew that their statements were going to be made known to the parties before the hearing," id., at 111, and proposed adding another exemption to make clear that "statements of agency witnesses" would be exempt "until such witnesses are called to testify in an action or proceeding," id., at 110. In direct response to what he described as Senator Humphrey's "valu

'Senator Humphrey's amendment would have exempted from disclosure "statements of agency witnesses until such witnesses are called to testify in an action or proceeding and request is timely made by a private party for the production of relevant parts of such statements for purposes of cross examination." 1974 Source Book 110. Colloquy on the floor made clear that the Senators thought it desirable to extend the so-called "Jencks" rule to agency proceedings, requiring the disclosure of witnesses' statements only after the witnesses testified at the agency proceedings. See id., at 111.

able suggestion," Senator Long offered an amendment resulting in the version of Exemption 7 actually passed in 1966, which Senator Humphrey agreed would "take care of the situation." Id., at 111.

In light of this history, the Board is clearly correct that the 1966 Act was expressly intended to protect against the mandatory disclosure through FOIA of witnesses' statements prior to an unfair labor practice proceeding. From one of the first reported decisions under FOIA, Barceloneta Shoe Corp. v. Compton, 271 F. Supp. 591 (PR 1967), through the time of the 1974 amendments, the courts uniformly recognized this purpose. Thus, in Wellman Industries, Inc. v. NLRB, 490 F. 2d 427 (CA4), cert. denied, 419 U. S. 834 (1974), the Court of Appeals held that affidavits obtained by an NLRB investigator during an inquiry into union objections to a representation election, which ultimately led to the filing of an unfair labor practice charge, were exempt from disclosure sought by the employer prior to the hearing on the complaint. It noted that employees might become unwilling to make " uninhibited and non-evasive statement [s]'" if disclosure were granted, 490 F. 2d, at 431, quoting NLRB v. National Survey Service, Inc., 361 F. 2d 199, 206 (CA7 1966), and emphasized that application of the exemption was "necessary in order to prevent premature disclosure of an investigation so that the Board can present its strongest case in court." 490 F. 2d, at 431. Accord, NLRB v. Clement Bros. Co., 407 F. 2d 1027, 1031 (CA5 1969).

C

In 1974 Congress acted to amend FOIA in several respects. The move to amend was prompted largely by congressional disapproval of our decision in EPA v. Mink, 410 U. S. 73 (1973), regarding the availability of in camera review of classified documents. Congress was also concerned that administrative agencies were being dilatory in complying with the