OPINION EN BANC
BREYER, Circuit Judge.
The plaintiffs in this case, academic historians researching the McCarthy Era, have sued the government under the Freedom of Information Act (“FOIA”), 5 U.S.C. § 552 (1982 & Supp. IV 1986). The plaintiffs want the Federal Bureau of Investigation (“FBI”) to give them information contained in the FBI’s Smith Act prosecutions file, information that would reveal what certain FBI informants, who testified at the Smith Act trials of alleged Communist leaders in the 1950s, had told the FBI (and other related material about those informants). The FOIA provides that “upon any request for records” following certain procedures, the agency “shall make the records promptly available to any person.” 5 U.S.C. § 552(a)(3). But this broad disclosure provision is limited by several exemptions. The FBI refused to release the files to the plaintiffs, relying on FOIA exemption 7(D), which permits the government to withhold records or information compiled for law enforcement purposes that:
could reasonably be expected to disclose the identity of a confidential source ... and, in the case of a record or information compiled by criminal law enforcement authority in the course of a criminal investigation or by an agency conducting a lawful national security intelligence investigation, information furnished by a confidential source.
5 U.S.C. § 552(b)(7)(D) (emphasis added).
The legal question presented in this case is whether, despite the exception to disclo[1447]*1447sure afforded the FBI by the literal terms of exemption 7(D), the information should nevertheless be made available to the plaintiffs on the ground that the “confidential sources,” by testifying at public trials concerning some of their communications to the FBI, “waived” the FBI’s right to invoke exemption 7(D). The district court held that, because the informants had testified in public about these matters, much of the requested information no longer fell within the scope of exemption 7(D). On appeal, a panel of this court held that informants, by actually testifying publicly, “waived” the protections of exemption 7(D), but only insofar as they then actually revealed the information in question or insofar as the information in question would have fallen within the “hypothetical scope of cross examination” at the previous public trial. 851 F.2d 532 (1st Cir.1988) (subsequently withdrawn). Cf. Irons v. F.B.I., 811 F.2d 681 (1st Cir.1987) (“Irons I”) (holding that mere willingness to testify publicly did not “waive” exemption 7(D)).
The government asked for rehearing en banc. It pointed out that FOIA’s disclosure windows are open to every member of the public: a rule of law that permits reputable historians to conduct historical research will permit, to the same extent, the most disreputable criminals to search out the identity and knowledge of those who inform against them. See United States Department of Justice v. Reporters Committee for Freedom of the Press, — U.S. -, 109 S.Ct. 1468, 1480-81, 103 L.Ed.2d 774 (1989) (“Congress ‘clearly intended’ the FOIA ‘to give any member of the public as much right to disclosure as one with a special interest [in a particular document]’,” quoting NLRB v. Sears, Roebuck & Co., 421 U.S. 132, 149, 95 S.Ct. 1504, 1515, 44 L.Ed.2d 29 (1975) (emphasis added)). The government argued, in light of the fact that the rule of law enunciated in this case will apply well beyond the present Smith Act context to the entire realm of investigations governed by exemption 7(D), that the portion of the panel’s rule italicized above (the portion dealing with cross-examination) would bring too much confidential information into the public domain. The government urged that this rule is not a legally permissible interpretation of exemption 7(D). We granted the petition for rehearing en banc, vacating and withdrawing the panel opinion. See 851 F.2d 532 (1st Cir.1988). We have reconsidered the district court’s interpretation and application of exemption 7(D), and we conclude that the government is correct about the generally applicable rule of law. For that reason these plaintiffs are not legally entitled to the information they seek.
I.
To understand our answer to the legal question now before us, the reader must keep the following background circumstances in mind. First, the law permits the FBI to withhold both (1) information that “could reasonably be expected to disclose the identity of a confidential source,” and (2) “information furnished by a confidential source” (where the FBI has received the information in the course of a criminal or national security intelligence investigation). 5 U.S.C. § 552(b)(7)(D).
Second, for purposes of this rehearing en banc, we take as given the fact that the relevant sources here are “confidential.” A person is a confidential source
“if the person provided information under an express assurance of confidentiality or in circumstances from which such an assurance could be reasonably inferred.” S.Rep.No. 1200, 93d Cong., 2d Sess. 13 (1974) U.S. Code Cong. & Admin. News, 6267, 6291 (Conference Report).
Lame v. United States Department of Justice, 654 F.2d 917, 923 (3rd Cir.1981). The sources here received the requisite “assurance of confidentiality.” See Keys v. United States Department of Justice, 830 F.2d 337, 345 (D.C.Cir.1987); Irons I, 811 F.2d at 686 (assurance of confidentiality is “ ‘inherently implicit in FBI interviews conducted pursuant to a criminal investigation’ ”) (quoting Miller v. Bell, 661 F.2d 623, 627 (7th Cir.1981) (per curiam), cert. denied, 456 U.S. 960, 102 S.Ct. 2035, 72 L.Ed.2d 484 (1982)) (citations omitted). [1448]*1448Sometimes, of course, the fact that a source later gave public testimony might show that a law enforcement agency never gave a valid assurance of confidentiality in the first place, see, e.g., Van Bourg, Allen, Weinberg & Roger v. N.L.R.B., 751 F.2d 982, 986 (9th Cir.1985); Poss v. N.L.R.B., 565 F.2d 654, 658 (10th Cir.1977); Climax Molybdenum Co. v. N.L.R.B., 407 F.Supp. 208, 209 (D.Colo.1975), aff'd on other grounds, 539 F.2d 63 (10th Cir.1976); and sometimes it might show that an assurance was intended by all parties to expire after a certain time, e.g. Nemacolin Mines Corp. v. N.L.R.B., 467 F.Supp. 521, 524-25 (W.D.Pa.1979). But such is not the situation here. Irons I, 811 F.2d at 685-86 & n. 2.
Third, the information here at issue falls within the literal language of the second clause of the exemption. That is to say, it was “furnished by a confidential source” (though long ago). The words “furnished by a confidential source” do not mean that the information or the identity of the source is secret; they simply mean that the information was “provided in confidence” at the time it was communicated to the FBI. Shaw v. F.B.I., 749 F.2d 58, 61 (D.C.Cir.1984); L & C Marine Transport, Ltd. v. United States, 740 F.2d 919, 925 n. 8 (11th Cir.1984); Radowich v. United States Attorney, District of Maryland, 658 F.2d 957, 959 (4th Cir.1981); Keeney v. F.B.I., 630 F.2d 114, 117, 119 n. 2 (2d Cir.1980).
Fourth, we are not considering the FBI’s refusal to make available information restating what the sources in fact revealed at the Smith Act trials. In this dispute the government does not contest the plaintiffs’ right to obtain documents that reveal no more than what the FBI sources have already revealed at trial, even though other courts have upheld, under exemption 7(D), the FBI’s refusal to disclose such information. See L & C Marine Transport, 740 F.2d at 925 (law enforcement agencies need not disclose information about source identity even though the source’s identity is already publicly known); Radowich, 658 F.2d at 960 (same); Lame, 654 F.2d at 925 (“subsequent release or publication ... of a portion of the information [originally given in confidence] does not negate the exemption for any of the information originally given”) (emphasis added; footnote omitted); Lesar v. United States Department of Justice, 636 F.2d 472, 491 (D.C.Cir.1980) (same). We focus here only upon the plaintiffs’ claim that they are entitled to more than what the Smith Act trials in fact brought to light.
One might wonder, in light of what we have just written, how the plaintiffs could plausibly claim that they are entitled to the information they seek. After all, most of the information sought falls within the plain language of exemption 7(D): “information furnished by a confidential source.” Why, at least in respect to this information, is the literal language not the end of the matter? The reason that the plaintiffs’ claim is plausible is that some courts have written opinions that use the word “waiver” when discussing exemption 7(D); one might therefore argue that a “confidential source” could “waive” the exemption and that the statute foresees courts defining the scope of any such “waiver.” See, e.g., Ingle v. Department of Justice, 698 F.2d 259, 269 (6th Cir.1983); Miller v. Bell, 661 F.2d at 628; Radowich, 658 F.2d at 960; Powell v. United States Department of Justice, 584 F.Supp. 1508, 1530 (N.D.Cal.1984). The plaintiffs argue that the sources’ testifying amounted to such a “waiver.” Indeed, the panel in the present case agreed and undertook the difficult task of defining a “waiver’s” scope.
Thus, as mentioned at the outset, the legal question before us is whether the law requires us to interpret the language of exemption 7(D) rather literally or whether we may interpret it as embodying some kind of “waiver” doctrine. To answer this question, we have examined the statute, its history, and the case law in some detail. We have concluded that we must take the statute here to mean what it says.
II.
Our reasons for concluding that the information sought here falls within exemp[1449]*1449tion 7(D), and that the concept of “waiver” does not apply, are the following:
First,
The starting point in statutory interpretation is “the language [of the statute] itself.” Blue Chip Stamps v. Manor Drug Stores, 421 U.S. 723, 756 [95 S.Ct. 1917, 1935, 44 L.Ed.2d 539] (1975) (Powell, J., concurring). “[W]e assume that the legislative purpose is expressed by the ordinary meaning of the words used.” American Tobacco Co. v. Patterson, 456 U.S. 63, 68 [102 S.Ct. 1534, 1537, 71 L.Ed.2d 748] (1982) [citation omitted].
United States v. James, 478 U.S. 597, 604, 106 S.Ct. 3116, 3120, 92 L.Ed.2d 483 (1986). Accord Allende v. Schultz, 845 F.2d 1111, 1116-17 (1st Cir.1988). The language of the exemption’s second clause, giving all its words their “ordinary meaning,” permits the government to withhold “information furnished by a confidential source” to a “criminal investigation ... or national security intelligence investigation.” 5 U.S.C. § 552(b)(7)(D). This language squarely applies here. Neither this language, nor any other relevant language, says anything at all about “waiver.” Other courts (indeed virtually all other courts) have interpreted the statute’s language literally in this respect. The Third Circuit, for example, has said that “all the information given by a confidential source is exempt,” that “the release of a portion of such information does not lift the blanket exemption,” and that the “subsequent disclosure of information originally given in confidence does not render nonconfidential any of the information originally provided.” Lame, 654 F.2d at 925 (3d Cir.1981) (emphasis added). See also Kiraly v. F.B.I., 728 F.2d 273, 278-80 (6th Cir.1984); Lesar, 636 F.2d at 491-92 (D.C.Cir.1980); Scherer v. Kelley, 584 F.2d 170, 176 n. 7 (7th Cir.1978), cert. denied 440 U.S. 964, 99 S.Ct. 1511, 59 L.Ed.2d 778 (1979). Accord L & C Marine Transport, 740 F.2d at 923-25 (11th Cir.1984) (same in a case of civil law enforcement); Brown v. F.B.I., 658 F.2d 71, 75 (2d Cir.1981) (same for a related FOIA exemption). We ourselves have made clear that the district courts are not to balance interests under exemption 7(D), but rather simply to apply the criteria listed in the statute. Irons I, 811 F.2d at 685 (“the judiciary is not permitted to undertake a balancing of conflicting interests, but is required to uphold a claimed 7(D) exemption so long as the statutory criteria are met.”). Accord Curran v. Department of Justice, 813 F.2d 473, 474 (1st Cir.1987); L & C Marine Transport, 740 F.2d at 925; Lame, 654 F.2d at 923; Lesar, 636 F.2d at 492; Sands v. Murphy, 633 F.2d 968, 971 (1st Cir.1980).
Second, the fairly elaborate legislative history of exemption 7(D) suggests that Congress intended a literal interpretation, even where a literal application sweeps broadly. That history makes clear that Congress enacted the exemption in major part to help law enforcement agencies to recruit, and to maintain, confidential sources; its object was not simply to protect the source, but also to protect the flow of information to the law enforcement agency. See Irons I, 811 F.2d at 688 (policy of exemption 7(D) is to prevent “chilling effect on third parties [which] would significantly limit the prospective flow of information to the sovereign”); Church of Scientology of California v. United States Department of Justice, 612 F.2d 417, 423-26 (9th Cir.1979) (surveying legislative history and concluding that exemption 7 was designed “so that law enforcement agencies would not be adversely affected in their lawful investigatory duties”); Scherer, 584 F.2d at 176 & n. 7; T.V. Tower, Inc. v. Marshall, 444 F.Supp. 1233, 1237 (D.D.C.1978) (“the fundamental purpose of exemption 7(D) [is] the enhancement of agencies’ enforcement abilities by permitting them to withhold [information]”).
The plaintiffs have suggested that the statute codifies a common law “informants’ privilege,” a privilege that one might waive; but the statute’s legislative history makes no significant reference to such a “privilege.” Rather, the legislators refer to their law enforcement policy goals. Plaintiffs point to a judicial decision, Westing house Electric Corp. v. City of Burlington, Vermont, 351 F.2d 762 (D.C.Cir.1965) (citing Roviaro v. United States, 353 [1450]*1450U.S. 53, 77 S.Ct. 623, 1 L.Ed.2d 639 (1957)), for the proposition that exemption 7(D) codifies a common law “informant’s privilege.” But Westinghouse expressly restricts the privilege of which it speaks to “the identity of the informer;” it says the privilege does not apply to the “content of the communication,” Westinghouse, 351 F.2d at 768. See Roviaro, 353 U.S. at 59-62, 77 S.Ct. at 627-29 (same). Thus, Congress’ subsequent enactment in 1974 of exemption 7(D)’s second clause protecting “information furnished” could not have reflected any “common law” aspect of the privilege discussed in Westinghouse. Cf Han v. Food & Nutrition Service, U.S.D.A., 580 F.Supp. 1564, 1568-69 (D.N.J.1984) (characterizing only “identity” clause of exemption 7(D) as a “privilege”). Nor do we think, in contrast to the dissent, post p. 1458, that Congress’ 1974 FOIA legislation necessarily embodied the exact views of FOIA set forth a year earlier by the Supreme Court, see EPA v. Mink, 410 U.S. 73, 93 S.Ct. 827, 35 L.Ed.2d 119 (1973), or nine years earlier in the 1965 Senate Report relied on by Mink, 410 U.S. at 80, 93 S.Ct. at 832.
Instead, the second clause of exemption 7(D) responds to President Ford’s criticisms of an initial version of the Freedom of Information Act, in particular the criticism that it might hinder law enforcement efforts. See Keeney, 630 F.2d at 118; Church of Scientology, 612 F.2d at 422-23, 425. Congress responded by modifying exemption 7(D), adding the second clause’s language protecting “information furnished by a confidential source.” In doing so, the Act’s sponsors made statements suggesting an intent to have this language apply broadly and therefore quite literally. Senator Phillip Hart, for example, one of the chief architects of the exemption, explained the meaning of the language in question as follows:
The major change in conference was the provision which permits law enforcement agencies to withhold ‘confidential information furnished only by a confidential source’. In other words, the agency not only can withhold information which would disclose the identity of a confidential source but also can provide blanket protection for any information supplied by a confidential source. The President is therefore mistaken in his statement that the FBI must prove that disclosure would reveal an informer’s identity; all the FBI has to do is to state that the information was furnished by a confidential source and it' is exempt. In fact, this protection was introduced by the conferees in response to the specific request of the President in a letter to Senator Kennedy during the conference. All of the conferees endorsed the Hart amendment as modified.
Source Book: Legislative History, Texts, and Other Documents, Freedom of Information Act and Amendments of 1974 (P.L. 93-502), Joint Committee Print, March 1975, at 451 (“Source Book”), quoted in Radowich, 658 F.2d at 962 (emphasis added). Despite these changes, President Ford vetoed the bill, and Congress acted to override the veto. See Radowich, 658 F.2d at 963; Keeney, 630 F.2d at 118; Church of Scientology, 612 F.2d at 423. Speaking in favor of the override, Senator Kennedy, the Chairman of the Senate conferees, then reassured the Senate:
Then we also provided [in 7(D)] that there be no requirement to reveal not only the identity of a confidential source, but also any information obtained from him in a criminal investigation. The only source information that would be available would be that compiled in civil investigations.
Source Book at 459, quoted in Radowich, 658 F.2d at 963. And Senator Byrd, the Senate majority leader, added that any fear that the Act would hinder law enforcement was groundless in light of the new language in 7(D). He said:
The Senate-passed version of the bill contained an amendment which would have required disclosure of information from a law enforcement agency unless certain information was specifically exempted by the act. What particularly disturbed me was that while the identity of an informer would be protected, the confidential information which he [1451]*1451had given the agency would not have been protected from disclosure .... I was deeply concerned that without such protection, law enforcement agencies would be faced with a ‘drying-up’ of their sources of information and their criminal investigative work would be seriously impaired.
The bill in the form now presented to the Senate has been significantly changed by the conference on these critical issues.... The language has also been broadened substantially to protect from disclosure all of the information furnished by a confidential source to a criminal law enforcement agency if the information was compiled in the course of a criminal investigation.
Source Book at 468, quoted in Radowich, 658 F.2d at 963-64 (emphasis added).
Contrary to the dissent, see post pp. 1459-1460, we believe that Senator Byrd had reason to say what he did, and therefore to have meant what he said. Consider the informant who testifies in public and reveals at trial (i) that Joe participated in an organized crime numbers racket, but who does not say that he has also confidentially told the FBI (ii) that Wes, Lola, George, and Yvette were also involved and that the racket included loan sharking, bribery, and murder. The disclosure of item (i), and of the informant’s identity as the source of that information, may lead the informant to fear reprisals from Joe’s friends; but the disclosure of item (ii), and of the informant’s role as the source of it, could mean far more in the way of reprisals from friends of Wes, Lola, George and Yvette. One can understand why confidential sources might hesitate to talk if disclosure at trial of something like item (i) means that organized criminals have the legal right to obtain the information in item (ii) from the FBI through the FOIA, information that the defendants at trial legally could ask about but would not be likely to, say because of its damaging implications for Joe or because of its more minor importance to the trial of Joe. See infra pp. 1455-1456. Thus, even though one might debate the relevant probabilities of any or all of these events, across the minerun of typical cases, one can see why Senator Byrd might have expressed concern.
Congress may also have wanted the law to contain the language it wrote in 7(D), because the other exemptions in exemption 7 offer somewhat narrower protection. Exemption 7(A), for example, authorizes withholding information whose disclosure “could reasonably be expected to interfere with enforcement proceedings,” 5 U.S.C. § 552(b)(7)(A). It does not apply to sources who cooperated in now-completed enforcement proceedings. Exemption 7(C) only applies when disclosure could work an “unwarranted invasion of personal privacy;” such invasion might, or might not, be found when the source’s information is about other persons, say those who have already been convicted; and in any event, the exemption erects a balancing test which gives the source less guarantee of confidentiality. Exemption 7(E), which applies when production of the information “would disclose techniques and procedures for law enforcement investigations or prosecutions,” 5 U.S.C. § 552(b)(7)(E), does not protect sources’ information about the acts of others unless disclosure indicates how the agency investigated the case. And, exemption 7(F), while authorizing withholding of information which “could reasonably be expected to endanger the life or physical safety of any individual,” 5 U.S.C. § 552(b)(7)(F), says nothing about nonphysical threats, such as a business boycott or cruel harassment of vulnerable family members. Nor does 7(F) clearly protect against threats that the FOIA judge cannot assess in some reasonably concrete terms — a particular problem when the information concerns events in the more distant past. Taken together these exemptions do not reach every important corner of exemption 7(D)’s domain. Thus, it is not unreasonable to believe that Congress, both in the words of 7(D) and in its legislative history, meant what it said.
In sum, the history is not ambiguous. It shows that in 1974 the Congress, anxious to strengthen a Freedom of Information Act applicable to nearly all the federal government, sought to lessen opposition to [1452]*1452the proposal by simultaneously enacting a broad exemption for law enforcement. In 1986, Congress acted again to broaden exemption 7(D), making certain wording changes (such as the deletion of the word “only” after the words “information furnished”) so as to “broaden the reach of this exemption and to ease considerably a Federal law enforcement agency’s burden in invoking it.” 199 Cong.Rec. S16504 (daily ed. October 15, 1986) (statement of Sen. Hatch), quoted in Irons I, 811 F.2d at 687. Since the words of the statute say nothing about a waiver doctrine, and since there is no “clearly expressed legislative intention to the contrary,” the statute’s plain language must “be regarded as conclusive.” CPSC v. GTE Sylvania, Inc., 447 U.S. 102, 108, 100 S.Ct. 2051, 2056, 64 L.Ed.2d 766 (1980). Even were we to read the history for its least significance, it would indicate that, before courts find any “waiver” of exemption 7(D)’s protections, they must consider the interests of the law enforcement agency as well as those of the source; and this fact, in turn, would have to mean that “waiver” by “sources” will not automatically prove sufficient to release the information.
Third, given this history, it is not surprising to find, as we have already pointed out, that the circuits have not only used broad language to describe the application of exemption 7(D), see supra pp. 1449, but that they have also specifically interpreted the “information furnished” exemption to apply irrespective of subsequent public identification of the source, see L & C Marine Transport, 740 F.2d at 925; Kiraly, 728 F.2d at 278; Radowich, 658 F.2d at 960, and irrespective of subsequent public release of portions of the information provided by the source, see Lame, 654 F.2d at 925; Lesar, 636 F.2d at 491; Scherer, 584 F.2d at 176 n. 7. Those courts concluded that FBI disclosure through the FOIA, by confirming what had become public through other sources, could nonetheless either harm the source or harm the agency’s ability to recruit other sources, and they therefore applied the literal language of exemption 7(D) to protect the information. They have also interpreted the exemption to apply irrespective of the nature of the information (so long as the information meets the criteria in the exemption). See Keys, 830 F.2d at 341, 345 (decades-old information); Weisberg v. United States Department of Justice, 745 F.2d 1476, 1492 (D.C.Cir.1984) (specific nature of information irrelevant); Diamond v. F.B.I., 707 F.2d 75 (2d Cir.1983) (McCarthy era information), cert. denied, 465 U.S. 1004, 104 S.Ct. 995, 79 L.Ed.2d 228 (1984); Lesar, 636 F.2d at 492 (specific contents of information not relevant); Lamont v. Department of Justice, 475 F.Supp. 761 (S.D.N.Y.1979) (McCarthy era Smith Act documents).
Fourth, while courts in some exemption 7(D) cases have used the word “waiver,” see supra 1448 and infra 1454-56, they have not used that word in any context or in any way that argues for application of a “waiver doctrine” in the type of case before us.
Courts generally use the concept of “waiver” in the law in four related sorts of circumstances. (1) Courts sometimes say an individual has “waived” a protection the law grants him when the individual expressly says that he wishes to do without the protection. See, e.g., Miranda v. Arizona, 384 U.S. 436, 475, 86 S.Ct. 1602, 1628, 16 L.Ed.2d 694 (1966) (“express statement ... could constitute a waiver” of Fifth Amendment right against self-incrimination); Regional Properties, Inc. v. Financial & Real Estate Consulting Co., 752 F.2d 178, 183 (5th Cir.1985) (“waiver of rights [to rescind a contract] may result where a party demonstrates intentional relinquishment of rights of which the party has full knowledge”). See also Irons I, 811 F.2d at 686 (citing cases of intentional express waiver).
(2) Courts sometimes infer from an individual’s statements or conduct that the individual wishes to forego a protection, even though the courts remain somewhat uncertain about what the individual would really say were he presented with the choice anew before the court. See, e.g., United States v. Gann, 732 F.2d 714, 722-23 (9th Cir.), cert. denied, 469 U.S. 1034, [1453]*1453105 S.Ct. 505, 83 L.Ed.2d 397 (1984) (communication in presence of third party indicates that communication’s confidentiality for purposes of attorney-client privilege is waived); 2 J. Weinstein & M. Berger, Weinstein’s Evidence 503-37 & n. 5 (1988 & Cum. Supp. May 1988) (same); United States v. Collins, 690 F.2d 431, 439 (5th Cir.1982) (party may not complain on appeal of errors invited or induced by its own conduct at trial), cert. denied, 460 U.S. 1046, 103 S.Ct. 1447, 75 L.Ed.2d 801 (1983); United States v. Krynicki, 689 F.2d 289, 291 (1st Cir.1982) (failure to raise issue at trial waives right to appeal on that ground). See also Irons I, 811 F.2d at 686-87 (citing cases on waiver implied by conduct).
(3) Courts may also use the word “waiver” as a way of insisting that an individual forego protection which he says that he does not wish to give up but which he has agreed to give up in the past. See, e.g., Schmid v. National Bank of Greece, 622 F.Supp. 704, 714-15 (D.Mass.1985) (enforcing contractual release of right to sue other party), aff'd, 802 F.2d 439 (1st Cir.1986); Anselmo v. Manufacturers Life Insurance Co., 595 F.Supp. 541, 549-51 (W.D.Mo.1984) (enforcing contractual release of right to sue, and encouraging settlements incorporating such releases), aff'd, 771 F.2d 417 (8th Cir.1985); Wilhelm v. Baxter, 436 F.Supp. 1322, 1326-27 (S.D.Ill.1977) (finding purchase of liability insurance to waive local government’s immunity from suit).
(4) Finally, courts sometimes insist that an individual forego protection that he does not wish to give up, in order to avoid unfairness to others, such as adversaries in litigation who might suffer harm were a factfinder to be misled, say, by a partial disclosure of relevant information. Thus the “rule of completeness” provides for “the right of the opponent, against whom the utterance is offered, to put the remainder in evidence on cross-examination or as part of his case.... subject to the general principles of relevancy,” 1 J. Weinstein & M. Berger, Weinstein’s Evidence H 106[02] at 106-17 (1988), even though the remainder would not by itself have been admissible. See 7 J. Wigmore, Evidence §§ 2094-125 (Chadbourn rev.1978) (formulating rule of completeness); United States v. LeFevour, 798 F.2d 977, 980-82 (7th Cir.1986) (discussing alternative remedies); United States v. Pierre, 781 F.2d 329, 331 (2d Cir.1986) (rule as applied to prior consistent statements); Brewer v. Jeep Corp., 724 F.2d 653, 657 (8th Cir.1983); United States v. Rubin, 609 F.2d 51, 63 (2d Cir.1979), aff'd on grant of certiorari limited to other issue, 449 U.S. 424, 428, 101 S.Ct. 698, 700, 66 L.Ed.2d 633 (1981); id., 609 F.2d at 70 (Friendly, J., concurring) (“the great principle of completeness”); United States v. Jamar, 561 F.2d 1103, 1108-09 (4th Cir.1977); United States v. Fayette, 388 F.2d 728, 733-34 & n. 2 (2d Cir.1968). See also Fed.R.Evid. 410 (last paragraph, part (i): otherwise inadmissible statement from plea negotiation is admissible where another statement from that negotiation has been introduced and fairness requires that the statements be considered together). Similarly, courts have held that a defendant’s voluntary act of taking the stand to testify on his own behalf waives his Fifth Amendment right against self-incrimination, because otherwise the defendant could unfairly reveal to the jury partial information supporting his case while claiming immunity to cross-examination about the rest of the story. See Brown v. United States, 356 U.S. 148, 154-56, 78 S.Ct. 622, 626-27, 2 L.Ed.2d 589 (1958); United States v. Black, 767 F.2d 1334, 1341 (9th Cir.), cert. denied, 474 U.S. 1022, 106 S.Ct. 574, 88 L.Ed.2d 557 (1985).
The first example is obviously inapplicable here, where neither source nor agency has asserted any intention to “waive” exemption 7(D). Nor is it sensible to apply “waiver” of the second variety, waiver reflecting a court’s efforts to infer from surrounding circumstances that the source himself actually wishes disclosure. That is because exemption 7(D) is not designed solely to protect the source. As discussed above, it mainly seeks to protect law enforcement agencies in their efforts to find future sources. Any legal principle that finds “waiver” and then requires disclosure in ambiguous circumstances would work [1454]*1454against that statutory end. To reach this conclusion one need not believe that sources make fine spun risk-benefit calculations (e.g., “I’ll talk to the FBI if I’ll only run the risk of eventually testifying and being cross-examined, but I won’t talk if an FOIA requestor can get the information”). One need only, and more reasonably, believe that, as a general matter, the more confidential information that appears in public (contrary to the true desire of the source), the harder it becomes for the law enforcement agency to recruit confidential sources. That being so, there is no reason to apply the “waiver” doctrine where not only is there no indication that the sources actually wanted to make public the information they did not in fact made public, but also the agency itself does not want such disclosure. There is no reason to apply concepts of express waiver or waiver inferred from conduct — notions applicable in other legal contexts — to the information now at issue before us.
The last two mentioned examples— where courts force an individual to give up protection against the individual’s stated wishes — are irrelevant in this type of Freedom of Information Act case, where the relevant “individual” is not the informant but the law enforcement agency. No one here has agreed to give up protection. Certainly the relevant party — the law enforcement agency — has never agreed to give up the exemption’s protection. Nor does “fairness” between parties require disclosure. This type of case arises outside the context of litigation; the concerns about self-serving incomplete testimony before a jury, which motivated the courts in crafting the “rule of completeness” and in deciding that the act of testifying waives the right against self-incrimination, are not prompted by a FOIA request. Considerations of an adversarial kind of fairness as between the public (the requestors of the information) and the source (who disclosed information to the agency) are not present in the FOIA context. There is no reason grounded in fairness for requiring a source who disclosed information during testimony to reveal, against his will (or to have the FBI reveal for him), information that he did not disclose in public.
Examination of the circuit court cases that refer to “waiver” in the context of exemption 7(D) reveals that those cases are not relevant in the present context. We have found five kinds of exemption 7(D) cases that use the word “waiver.” (1) In some cases, the courts have held that a source “waived” confidentiality by later explaining that, before he or she provided the agency with information, the source had not expected the information would be kept confidential. Those cases are different from this one because the courts in those cases held that the source simply was not a “confidential source.” See Miller v. Bell, 661 F.2d at 627-28 (finding one witness’ information not within exemption 7(D) because she asserted that she had never received assurances of confidentiality; also reaffirming Scherer, 584 F.2d 170, which had held no waiver despite public testimony by the source). Here the source was “confidential” and the information was “furnished by a confidential source.” See supra 1447-1448. (2) In other cases courts have said that even though the relevant information already is public, the FBI nonetheless need not disclose it because the source has not “waived” the exemption. See Radowich, 658 F.2d at 960; Lesar, 636 F.2d at 491. Such cases, in forbidding disclosure of already public information, obviously do not hold that the FBI must reveal information that has not previously been made public. (3) Still other cases state that public testimony does not “waive” protection of information not made public. See Scherer, 584 F.2d at 176 n. 7 (“we reject Scherer’s argument [that the source ‘relinquished’ its right to nondisclosure]. Because a person may have given testimony at a trial on a specific topic does not mean that all information offered by that source upon a guarantee of confidentiality automatically becomes available to the person to whom it relates.”). These cases support the government, not the plaintiffs. (4) One case says that the FBI cannot “waive” the protection the exemption gives the source. Ingle v. Department of Justice, 698 F.2d 259 (6th Cir.[1455]*14551983). That case says nothing about when, or whether, a source might “waive” protection thereby requiring the FBI to disclose against its will. (5) A single district court case does hold that actual testimony waives the right to nondisclosure. Powell, 584 F.Supp. at 1529-30 (N.D.Cal.1984). That case, however, speaks only about the waiver of the right to withhold a source’s “identity” once the source has testified; it says nothing about disclosure of the information furnished by the source. In addition, the Powell court apparently thought “confidential” meant “secret” at the time of the FOIA request, id. at 1529, which, as we have noted above, supra 1448, is not the proper interpretation of the term under exemption 7(D) (rather, “confidential” under 7(D) means “provided in confidence” to the agency).
The plaintiffs also point to several labor law cases interpreting exemption 7(D). Those eases, however, are beside the point. For one thing, those cases concern an issue different from the one before us. They consider whether a source, knowing he is likely to testify at the time he furnishes information to the agency, is, or remains after testimony, a “confidential source” within the meaning of the statute — a point not here in issue. See Van Bourg, 751 F.2d at 986; Poss, 565 F.2d at 658; Nemacolin Mines, 467 F.Supp. at 524; Mylan Pharmaceuticals, Inc. v. N.L.R.B., 407 F.Supp. 1124, 1127 (W.D.Pa.1976); Climax Molybdenum, 407 F.Supp. at 209. See supra 1447-48 (sources here are “confidential”). In addition, these labor cases involve civil law enforcement, not criminal law enforcement; hence, they involve only the first clause of exemption 7(D), the clause that protects the “identity of a confidential source,” not the second clause that protects “information compiled by a criminal law enforcement authority in the course of a criminal investigation [and] furnished by a confidential source.” 5 U.S.C. § 552(b)(7)(D). See statement of Sen. Kennedy, supra; Keys, 830 F.2d at 343; Akron Standard Division of Eagle-Picher Industries, Inc. v. Donovan, 780 F.2d 568, 573, petition for reh’g denied, 788 F.2d 1223 (6th Cir.1986); Lame, 654 F.2d at 923. Further, the cases involve OSHA and the NLRB, different enforcement agencies, operating in different statutory and institutional contexts, where sources may have different expectations. It may be, for example, that an NLRB source knows from the beginning that he will have to testify and that his employer will discover his identity; it may be that an FBI source does not know whether he will have to testify and, in any event, believes that testimony will not necessarily reveal all the “information” he has “furnished” the FBI. Finally, the circuits themselves are in conflict over the holding that the sources are not “confidential,” even in the labor law enforcement and statutory context in which they arise. Compare United Technologies Corp. v. N.L.R.B., 777 F.2d 90 (2d Cir.1985) (finding source is confidential and no waiver); L & C Marine Transport, 740 F.2d 919 (no waiver), with Van Bourg, 751 F.2d 982 (not confidential); Poss, 565 F.2d 654 (same); Nemacolin Mines, 467 F.Supp. 521 (same); Mylan Pharmaceuticals, 407 F.Supp. 1124 (same); Climax Molybdenum, 407 F.Supp. 208 (same). The one circuit that has directly considered whether its “labor context” holding applies in the criminal law context has indicated that it does not. Akron Standard Division of Eagle-Picher Industries v. Donovan, 788 F.2d 1223 (6th Cir.1986) (denying petition for rehearing en banc) (“we wish to make it clear that we do not thereby abandon the analysis of this court in Kiraly ” (which concluded, in the “criminal context,” that testimony by a source does not waive exemption 7(D))).
In a nutshell, some cases use the word “waiver” in the context of saying that a person was not a “confidential source;” others use it in the context of saying protection was not “waived.” Those cases do not support the proposition that courts may declare a “waiver,” over an agency’s objection, of the protections the statute gives to information that was furnished by a confidential source.
Fifth, the judicial effort to create a “waiver” exception to exemption 7(D)’s language runs afoul of the statute’s “intent to provide ‘workable’ rules.” FTC v. Grolier, [1456]*1456Inc., 462 U.S. 19, 27, 103 S.Ct. 2209, 2214, 76 L.Ed.2d 387 (1983); accord Reporters Committee for Freedom of the Press, 109 S.Ct. at 1485; EPA v. Mink, 410 U.S. at 80, 93 S.Ct. at 832. Consider, for example, the serious problems posed by the “hypothetical scope of cross examination” rule that the dissent advocates here. That rule would permit any member of the public to obtain now any information that a confidential source furnished to the FBI in years past if that source ever testified about any matter at all and the confidential information might have emerged in response to questions that a cross examiner did not ask but, under the law, might have asked. The dissent concedes that this includes “a range of questions” on “a queue of topics,” infra 1462.
In evaluating the workability of this rule, we note (1) the fact that cross examiners typically ask of their witnesses only a tiny fraction of the questions the law permits them to ask; (2) the fact that lawyers often have a fairly good idea of what cross examiners will not ask about, say, for example, because a defense attorney will not want a testifying source to reveal before the jury all the bad things the source knows about the defendant; and (3) the fact that the judge trying to apply the “hypothetical scope of cross examination” rule is not the judge at the original trial where the source first testified, but is rather the judge at the later FOIA proceeding, where neither the source, nor his counsel, nor the original cross examiner is likely to be present, and which may take place months or years after the original trial.
These three facts pose grave difficulties for the FOIA-suit judge. What rules of evidence are to govern — those presently in effect, in the FOIA-suit jurisdiction, or those of, say, forty years ago when the original trial took place, and in the trial’s jurisdiction? How is the FOIA judge to resolve these legal issues? Must she imagine evidentiary rulings on innumerable hypothetical questions? Can she think herself back into the original proceeding in order to determine how that earlier judge might have ruled on the permissible scope of cross examination? Has she given adequate weight, say, to the fear of reprisals that might have affected those earlier rulings, and should she consider such fears?
The prosecutor at the original trial will also face substantial problems in trying to decide whether to have a source testify. The prosecutor might well believe, to use our earlier example, that if the source testifies about Joe’s numbers racket, the practical chances that Joe’s attorney will wish to delve into related bad conduct by the defendant’s somewhat distant associates is small; but under the dissent’s rule, the prosecutor must also consider the fact that an FOIA suit could force the FBI to make public all these matters so long as Joe’s attorney could legally have asked about them. Can the prosecutor run this additional risk to his source and to his ability to recruit new sources?
No less troublesome will be the position of potential sources. Of course, they must always realize that the information they give might someday become public, particularly if they testify. But, under the dissent’s rule, can they think other than: “If I testify about anything, the public — including those I implicate — will see everything "?
Given these practical problems, we can understand (1) why exemption 7(D) contains language that, without qualification, exempts from disclosure “information furnished by a confidential source;” (2) why the statute’s legislative history shows that Congress meant what it said; (3) why the case law (with one possible district court exception) rejects any effort to create a “waiver” doctrine where “information” has been “furnished by a confidential source;” and (4) why, despite the sympathetic factual circumstances of the case now before us, the law requires us to draw a line that groups this case with many others in which the need not to disclose is obviously paramount.
III.
For these reasons, we hold that public testimony by “confidential sources” cannot “waive” the FBI’s right under the second [1457]*1457clause of exemption 7(D) to withhold information furnished by a confidential source” and not actually revealed in public. For basically similar reasons, the first clause of exemption 7(D), protecting information that could reveal “the identity of a confidential source,” is not “waived” (notwithstanding subsequent public testimony by the source), insofar as disclosure of information not contained in the public testimony could confirm the source’s identity as to some information, or could reveal the source’s identity as the provider of other not-yet-disclosed information. Consequently, the plaintiffs are not entitled to information furnished to the FBI by confidential sources, beyond what has been actually disclosed in the source’s prior public testimony.
The judgment of the district court is vacated. This case is remanded for further proceedings consistent with this opinion.