Opinion for the Court filed by BAZELON, Chief Judge.
Concurring Opinion filed by LEVEN-THAL, Circuit Judge.
Dissenting Opinion filed by WILKEY, Circuit Judge, with whom MacKINNON, Circuit Judge, joins.
BAZELON, Chief Judge:These consolidated cases are before the court en banc on appeals by the Federal Trade Commission (FTC) from orders of the district court granting enforcement in part and denying enforcement in part with respect to administrative subpoenas duces tecum issued by the FTC to appellees, seven natural gas producers.1 The subpoenas in question were authorized by the FTC in aid of a formal investigation into the procedures employed by various natural gas producers in reporting their gas reserves — an investigation stemming primarily from an unprecedented decline in these reported reserves. That this nation currently is in the midst of an energy crisis, however defined, need not be detailed by this court. -The extent of the energy shortage, the reasons for it, and the appropriate governmental and industry responses to the problem are the focus of debate and investigation in various executive agencies and in Congress. Such questions are largely outside the province of the judiciary. In these cases we consider only the propriety of these investigative subpoenas in the context of the limited role assigned to the federal courts in enforcement proceedings.
I. FACTUAL BACKGROUND
A. The FTC Investigation
The American Gas Association (AGA), a trade association composed of producers, distributors, and marketers of natural gas, is recognized as one of the principal sources of authoritative statistical data concerning the natural gas industry. In 1945 the AGA established a Committee on Natural Gas Reserves to formulate annual estimates of proved reserves 2 for the benefit of the gas *395industry, the Government, and the general public. To facilitate this task, the Committee has subdivided the United States into ten regions and has assigned a subcommittee of its members to compile the gas reserve estimates for each area. Members of the subcommittees usually are employees of the gas producers, and each subcommittee member generally is assigned fields in which his employer is the major producer or has some other ownership interest.3
In May of 1969 the AGA for the first time reported a decline in the nation’s proved reserves, occurring in 1968. The reported decrease came on the heels of a Federal Power Commission (FPC) order instituting a proceeding to reconsider rates for the offshore portion of Southern Louisiana in light of the supply of gas reserves for that area.4 The AGA report for 1969, issued in May of 1970, revealed further declines in total reserves for the United States and, this time, in Southern Louisiana reserves as well. The Southern Louisiana area is generally acknowledged to be the most important gas-producing area in the nation, accounting for approximately one-third of our domestic natural gas production.5
By letter of September 1, 1970 to Commissioner McIntyre of the FTC, Senator Philip A. Hart, chairman of the Subcommittee on Antitrust and Monopoly of the Senate Judiciary Committee, stated that there were numerous allegations that natural gas producers were withholding information on gas reserves in order to obtain higher rates from the FPC and recommended that the Commission conduct an investigation to determine whether any activities in violation of section 5 of the Federal Trade Commission Act had occurred.6 On October 13, the Secretary of the Commission replied that “in order that the possibility of collusion or other unlawful conduct in this field may be more fully explored, we have today directed *396our staff to commence an investigation which will focus principally on the reporting, estimation, and deployment of reserves by the Natural Gas Industry in one selected area of the country.”7
After informal investigative efforts proved inadequate, the Bureau of Competition determined that the issuance of subpoenas would be necessary and so advised the Commission. On June 3,1971, the FTC issued a resolution directing the use of compulsory process in furtherance of a nonpublic investigation. The nature and scope of the investigation were stated as follows:
The purpose of the authorized investigation is to develop facts relating to the acts and practices of . [certain named corporations] to determine whether said corporations, and other persons and corporations, individually or in concert, are engaged in conduct in the reporting of natural gas reserves for Southern Louisiana which violates Section 5 of the Federal Trade Commission Act, or are engaged in conduct or activities relating to the exploration and development, production, or marketing of natural gas, petroleum and petroleum products, and other fossil fuels in violation of Section 5 of the Federal Trade Commission Act.8
During this period of the investigation the AGA cooperated with the FTC on a voluntary basis. Field-by-field estimates of each Southern Louisiana subcommittee member for the years 1966 through 1970 were made available for the Commission’s inspection and analysis in October 1971. The FTC staff also obtained data from reports filed with the FPC pertaining to gas reserves in Southern Louisiana.' These reports, known as Form 15 reports, are filed by interstate natural gas pipelines and list recoverable, saleable gas reserves committed to, collected by, or held by the reporting pipeline company. With information gained from these sources, as well as from numerous interviews and depositions, the FTC drafted a comprehensive subpoena duces tecum which was issued on November 24, 1971 to eleven natural gas producers.9
The FTC subpoena is premised on a thorough investigation of the producers’ estimation of gas reserves for the Southern Louisiana area, with a view towards comparison of the various estimates used by producers in their internal procedures and business operations with those reported as proved estimates to the AGA. To summarize briefly, Specifications A through F of the subpoena demand background information such as the company’s annual reports, subsidiaries, officers, customers, net production, and sales volume. Specification G requests documents and underlying data relating to all reserve estimates for the Southern Louisiana area made by the producers, both for internal purposes and for reports to the AGA, during the period 1962-1970. Specification H requires technical data concerning the location, operations, ownership interests, and drilling status of *397the fields and leaseholds for which estimates are provided pursuant to Specification G. Specification I seeks documents commenting on or otherwise relating to the preparation of various reserve estimates, the procedures employed therein, and the personnel involved. Specification I also requires, inter alia, documents relating to “lease nominations and bids, any agreements for joint or common leasing, exploration, development, production, purchase or sale, or any cash flow or economic feasibility studies preparatory to leasing, exploring, developing, purchasing or selling, which involve Offshore South Louisiana acreage.” Specification J requires various documents pertaining to reports of proved reserves to the AGA. Specification K asks for documents referring to any relation between the reporting of proved reserves and the rates for natural gas permitted by the FPC. Finally, Specification L demands the names of all employees involved in the estimating and evaluating process, together with their areas of responsibility.
All eleven gas producers filed motions to quash the subpoenas. On June 27,1972, the Commission denied the motions. During subsequent negotiations between the Commission’s staff and the gas producers, the Commission offered additional confidentiality protection for the information to be provided under Specifications G, H, and I;10 as a result, two producers agreed to comply in full with the subpoenas and one producer agreed to comply in part. The remaining producers refused to comply. Accordingly, petitions for enforcement were filed in the district court on June 4, 1973.11 Shortly thereafter, one other firm agreed to comply-
B. The FPC Proceeding
Roughly concurrently with the FTC’s investigation, the Federal Power Commission was conducting a ratemaking proceeding for the Southern Louisiana area. Since this proceeding figures prominently in the arguments of the gas producers, it will be discussed at this point. The FPC began considering area rates for Southern Louisiana in the early 1960’s, (So La I), but a final decision was not rendered until 1968.12 Almost immediately, and while So La I was still under review by the Fifth Circuit, the FPC instituted a new proceeding (So La II) to reconsider rates for the offshore portion of Southern Louisiana;13 a few months later, the Commission expanded the proceeding to include the entire area.14
The FPC was responding to numerous complaints that the supply-demand situation had changed significantly since the record in So La I was closed. The gas producers argued that present supplies were diminishing and that the rates established in So La I were inadequate to stimulate the development of new supplies. Various municipal distributors charged, however, that the producers were understating their reserves in reports to the AGA and were deliberately withholding natural gas. In December 1969 the FPC established procedures for the So La II proceeding and directed that a full evidentiary record be *398made on the reserve data question.15 As part of a staff investigation into the accuracy of the AGA data, the FPC ordered producers to furnish data relating to “uncommitted” natural gas reserves in the Southern Louisiana area;16 these estimates were confirmed by a staff-supervised spot audit. From an analysis of the pertinent Form 15 reports, the results of the uncommitted reserves study, and testimony from AGA officials, the FPC staff concluded that the AGA data was reliable. Following extensive evidentiary hearings before an administrative law judge, the record was certified to the entire Commission.
The FPC issued its decision in So La II on July 16, 1971 (shortly after the FTC resolution authorizing compulsory process in its investigation). The Commission discussed in some detail both the staff’s investigation and the contentions of several intervenors that producers had underreported their reserves.17 The Commission concluded that the AGA reserve data was “reasonably reliable for the [ratemaking] purposes used herein.” 18
C. Subsequent Litigation
Pursuant to the FTC’s petitions for enforcement of the subpoenas against the seven companies still refusing to comply, the district court held hearings on July 30 and December 13, 1973, and considered extensive briefs and other evidentiary materials filed by the parties. The two orders at issue here were filed on March 22, 1974. One order deals with the subpoenas issued to appellees Texaco, Inc., Standard Oil Co. (Indiana), Standard Oil Co. of California, Mobil Oil Corp., Shell Oil Co., and Exxon Corp.; the other order pertains to the subpoena issued to Superior Oil Co., Inc. The orders granted in part and denied in part the FTC’s petitions.
The exact basis for each modification made by the district judge is unclear. In the introductory paragraph of the first order, the court noted that the gas producers had contended “that the principles of primary jurisdiction and collateral estoppel preclude the Trade Commission from seeking the demanded documents or data for purposes of determining the validity or accuracy of natural gas reserve estimates, and . that certain demands of the subpoenas are irrelevant to any proper subject or area of investigation and are unduly broad and burdensome . . .” Without specifically ruling on these arguments in relation to each demand in the subpoenas, the court stated that:
being of the opinion that the Trade Commission is authorized to pursue the investigation to determine whether there exists any evidence of conspiracy in the reporting of proved natural gas reserve estimates to the American Gas Association by respondents, but that the subpoenas duces tecum are improper inso*399far as they seek data for the purposes of enabling the Trade Commission to attempt to determine natural gas reserves or the validity or accuracy of natural gas reserve estimates, matters already considered and ruled upon by the Federal Power Commission, and the Court being of the further opinion that the subpoenas are improper in other respects as well and should not be enforced as issued . . .”
In the first order the district court granted enforcement of Specifications A through F, dealing with background data; these specifications were not really contested by the parties. For Specifications G, H, and I, production of documents was limited to the years 1969, 1970, and 1971 and to a random sample of 100 out of approximately 225 offshore Southern Louisiana fields. Most importantly, production was limited to documents containing or underlying proved natural gas reserve estimates; “raw field data, bid calculation data, and bid calculation files” were specifically excluded. The court stated that all production pursuant to these three specifications “shall be made for the sole purpose of permitting the Trade Commission to investigate whether there is a conspiracy in the reporting of natural gas proved reserve estimates, and not for the purpose of permitting the Trade Commission to investigate or determine the amount of proved natural gas reserves.” In Specifications J and K production was limited to documents relating to proved reserves in only those offshore fields which were included in reports for 1971 by the AGA subcommittee for Southern Louisiana, and to documents from 1966 through 1971 “which were exchanged between or among, or constitute, contain or refer to any agreement, arrangement or communication between or among, respondent or others, including the American Gas Association”; production of intra-corporate documents was foreclosed. Specification L was limited to those employees who “acted with respect to proved natural gas estimates” for offshore Southern Louisiana during the period 1966 through 1971. For all specifications, the court granted the producer the option of producing the documents at the corporate office or field location where they were normally maintained, rather than at the FTC’s offices in Washington, D.C.; further, for documents furnished at a producer’s offices, the FTC was to bear any costs of reproducing the documents. Finally, the court provided further protection for any documents designated by the producer as confidential, ruling that, unless otherwise ordered by the court, such documents were to be held in the custody of the Commission’s Secretary, used only in the current investigation, inspected only by Commission employees assigned to the investigation, and returned to the producer at the completion of the investigation.
In the second order, relating to Superior, the district court enforced only Specifications A through F and K through L of the subpoena; Specifications G through J, requiring, inter alia, the production of reserve estimates, were quashed in their entirety. The same confidentiality protection accorded the other six producers also was granted to Superior. While no rationale was stated in the order, the different treatment for Superior apparently reflects an acceptance of Superior’s argument that because it had never been a member of the AGA and had not furnished reserve estimates to the AGA, it could not be involved in any conspiracy to underreport reserves.
On appeal, a panel of this Court affirmed the district judge’s orders, upholding all modifications of the subpoena except the limitation to data from 1969-1971 in Specifications G, H, and I — the FTC’s demand for documents from 1962-1971 was reinstated. The FTC petitioned for rehearing or rehearing en banc; on February 6, 1976 this court vacated the panel opinion and ordered the cases reheard en banc.
II. COURT ENFORCEMENT OF ADMINISTRATIVE SUBPOENAS — THE APPLICABLE LEGAL PRINCIPLES
The Supreme Court has made it clear that the court’s role in a proceeding to enforce an administrative subpoena is a *400strictly limited one. The seminal case is Endicott Johnson v. Perkins, 317 U.S. 501, 63 S.Ct. 339, 87 L.Ed. 424 (1943). The Endicott Court held that, on application for enforcement of a subpoena issued by the Secretary of Labor in administrative proceedings against the petitioner under the Walsh-Healy Public Contracts Act, the district court lacked authority to determine whether the corporation’s activities were covered by the statute. Rather the Court stated, since the evidence sought by the subpoena was not “plainly incompetent or irrelevant to any lawful purpose” of the Secretary, it was the district court’s duty to order its production for the Secretary’s consideration. Id. at 509, 63 S.Ct. at 343. Shortly thereafter, in Oklahoma Press Publishing Co. v. Walling, 327 U.S. 186, 66 S.Ct. 494, 90 L.Ed. 614 (1946), the Court applied the same principles to the enforcement of subpoenas issued pursuant to an investigation under the Fair Labor Standards Act.19 Rejecting any power in the district court to adjudicate coverage, the Court ruled that so long as the investigation was for a lawfully authorized purpose, the documents sought were relevant to the inquiry, and the demand was reasonable, the Administrator had a right to judicial enforcement of the subpoenas. See id. at 209, 66 S.Ct. 494. Emphasizing the importance of the administrative mandate to search out violations with a view to securing enforcement of the Act, the Court stated that while the Administrator may not act arbitrarily or in excess of his statutory authority, “this does not mean that his inquiry must be ‘limited . by forecasts of the probable result of the investigation’. . . . ” Id. at 216, 66 S.Ct. at 509 quoting Blair v. United States, 250 U.S. 273, 282, 39 S.Ct. 468, 63 L.Ed. 979 (1919).
In a case dealing directly with the investigative powers of the Federal Trade Commission, United States v. Morton Salt Co., 338 U.S. 632, 70 S.Ct. 357, 94 L.Ed. 401 (1950), the Court once again enunciated the standard: “. . . it is sufficient if the inquiry is within the authority of the agency, the demand is not too indefinite and the information sought is reasonably relevant.” Id. at 652, 70 S.Ct. at 369. In upholding the Commission’s order requiring certain corporations to file special reports demonstrating continuing compliance with a cease and desist order, the Court distinguished the judicial process, which does not involve itself in so-called “fishing expeditions” to determine if violations of law have occurred, from the administrative function of investigation:
The only power that is involved here is the power to get information from those who best can give it and who are most interested in not doing so. Because judicial power is reluctant if not unable to summon evidence until it is shown to be relevant to issues in litigation, it does not follow that an administrative agency charged with seeing that the laws are enforced may not have and exercise powers of original inquiry. It has a power of inquisition, if one chooses to call it that, which is not derived from the judicial function. It is more analogous to the Grand Jury, which does not depend on a case or controversy for power to get evidence but can investigate merely on suspicion that the law is being violated, or even just because it wants assurance that it is not. When investigative and accusatory duties are delegated by statute to an administrative body, it, too, may take steps to inform itself as to whether there is probable violation of the law. Id. at 642-43, 70 S.Ct. at 364.
Thus, while the court’s function is “neither minor nor ministerial,” Oklahoma Press Publishing Co. v. Walling, 327 U.S. at 217 n. 57, 66 S.Ct. 494, the scope of issues which may be litigated in an enforcement proceeding must be narrow, because of the important governmental interest in the expeditious investigation of possible unlawful activity. As the Ninth Circuit has noted, the “very backbone of an administrative agency’s effectiveness in carrying out the congressionally mandated duties of industry regulation is the rapid exercise of the power to investigate . . . .” FMC v. Port *401of Seattle, 521 F.2d 431, 433 (9th Cir. 1975).20
III. THE ISSUES
With these standards in mind, we turn to the issues at hand. The FTC’s allegations of error in the district court’s modifications of the subpoenas, and the producers’ arguments in response, focus on four general areas: 1) limitations apparently grounded on relevance, 2) application of some form of collateral estoppel to preclude certain aspects of the FTC’s investigation, 3) limitations premised on burdensomeness, and 4) conditions on use and possible disclosure of the documents.21
A. Relevance Determinations
1. Limitation to Documents Relating to Proved Reserve Estimates
The gas producers contend that the district court properly limited production to those documents relating to proved reserves on grounds of relevance.22 They argue that because the FTC’s investigation is targeted on a conspiracy to underreport reserves to the AGA, and only proved reserves are reported to the AGA, only proved reserves can be relevant to the inquiry. The FTC, on the other hand, maintains that its investigation cannot be so circumscribed, and that all reserve estimates made by the producers, both for various internal business purposes and for reports to the AGA, and however denominated, are relevant to access whether violations of section 5 of the Federal Trade Commission Act have taken place.
In resolving this controversy, we must determine whether the district judge’s limitation comports with the standard of “reasonable relevance.” 23 Where, as here, no complaint has yet been formulated and *402the issues have therefore not yet been crystallized, some courts have concluded that an attenuated standard of relevance is appropriate.24 In our view, however, the better approach is simply to recognize that in the pre-complaint stage, an investigating agency is under no obligation to propound a narrowly focused theory of a possible future case. Accordingly, the relevance of the agency’s subpoena requests may be measured only against the general purposes of its investigation. The district court is not free to speculate about the possible charges that might be included in a future complaint, and then to determine the relevance of the subpoena requests by reference to those hypothetical charges. The court must not lose sight of the fact that the agency is merely exercising its legitimate right to determine the facts, and that a complaint may not, and need not, ever issue.25
Under this frame of reference, the district court’s determination that only proved reserve estimates are relevant cannot withstand scrutiny. The relevance of the material sought by the FTC must be measured against the scope and purpose of the FTC’s investigation, as set forth in the Commission’s resolution.26 Here, however, the gas producers have posited — and the district court has apparently accepted — an erroneous interpretation of the scope of the FTC’s inquiry, and they have then sought to limit the investigation to the confines of this distorted interpretation. There is no merit to the producers’ contention that the FTC is only investigating possible underreporting of proved reserves to the AGA. The FTC’s resolution does not even mention either the AGA or proved reserves; further, in addition to “conduct in the reporting of natural gas reserves,” the resolution obviously incorporates a broad range of activities “relating to the exploration and development, production, or marketing of natural gas . . .” Although the FTC has never denied that reporting to the AGA *403is one aspect of its inquiry, it has repeatedly stated that its investigation cannot be so narrowly defined.27
Basically, the gas producers would have us believe that all the FTC has in mind is a recomputation of proved reserve estimates submitted to the AGA. On the contrary, the authorized inquiry envisions an examination of all phases of the estimating process. In particular, the FTC seeks to compare estimates prepared for various business purposes with those reported to the AGA. As Specification G of the subpoena indicates, producers may make reserve estimates in connection with bidding on or nominating leases; deciding whether or not to erect permanent platforms; compiling or inventorying total company reserves or supply; negotiating or contracting for the sale of natural gas, or for the joint or common exploration, development, production, purchase, or sale of acreage; obtaining bank loans; or filing depreciation expense schedules with the Internal Revenue Service. While some of these estimates may be labeled proved, some may not. Producers also may refer to certain reserve estimates as, inter alia, speculative, possible, or probable, depending on the stage of development of the field.
In order to assess whether proved reserve figures accurately reflect economic reality, reserve estimates with other labels •may be important; the same or substantially similar underlying data may give rise to distinctly denominated reserve estimates. In other words, the FTC may fairly inquire whether the companies, through the use of an excessively restrictive approach, have excluded awareness of certain realistic and reliable estimates which are taken into account in making significant business decisions but which are not labeled “proved” and are therefore not included in the AGA reports. As counsel for the FTC stated to the district judge, in explaining the relevance of the requested data,
This is relevant in determining whether AGA reserves reflect economic realities. Remember, those reserves are based on a definition of what constitutes a proved reserve but it may be that an examination of the company’s practices in the way it computes its reserves would show that the AGA reserve definitions are too restrictive, that in fact the companies themselves by their own conduct show that their reserves are more than what they would report to the AGA as proved reserves, or given a top and down estimate they may pick within a wide range, they may pick a top estimate for purposes where it serves their purposes, and a low estimate for other purposes where it serves their purpose.
App. II 368a-369a.
Thus, even if the FTC were investigating only the reporting of proved reserves (and we conclude that the inquiry is not so narrow), the analysis would certainly not be limited to whether the gas producers have accurately calculated their proved reserves. It is possible that such calculations are entirely in accord with the AGA’s definition of proved reserves, but that, in light of other estimates considered significant by the producers, this definition has an anti-competitive effect. The agreement of the producers, with each other, and with and through the AGA, to use such a restrictive definition as the exclusive method of projecting the industry’s position may have the effect — and, indeed, the purpose — of raising prices through its impact on purchasers and government. The FTC’s investigation is for the purpose of enabling it to determine whether the companies’ practices constitute an “unfair method of competition.” An unfair method of competition may result from concerted action even though there is no conspiracy by the dark of the moon. And as Morton Salt noted, the FTC may investigate either to develop the existence of a violation or to assure itself that none exists. 338 U.S. at 652, 70 S.Ct. 357.28
*404It is thus clear that the development and reporting of estimates at various stages of the investment and development process is reasonably relevant to the FTC’s purpose. We therefore hold that the district judge’s limitation of enforcement of the subpoena to only proved reserve estimates was erroneous.29
2. The Bid Files
In addition to ruling that only proved reserve estimates need be produced, the district court specifically found that “bid calculation data and bid calculation files” were irrelevant to the investigation, and therefore need not be produced.30 Like the district court’s general relevance determination, this more specific ruling is also premised upon the court’s erroneous delineation of the scope and purpose of the FTC’s investigation, and therefore, it, too, cannot be sustained.
Bid files are collections of documents developed for and used in nominating and bidding for the right to lease tracts in the federal domain for oil and gas exploration. According to the producers, bid files typically contain speculative reserve estimates, back-up data for such estimates — i. e., raw geological data and interpretation thereof, and documents reflecting the calculation of the producer’s bid.31
The producers maintain that bid files are not relevant to the determination of proved reserves, because bid files contain only speculative estimates which are of no further use once the company obtains a lease and begins exploratory drilling. The question, however, is not relevance to the calculation of proved reserves, but relevance to the FTC’s investigative purpose. Admittedly, bid file estimates are quickly superseded by more accurate data, are not used to compute proved reserve figures, and may be completely erroneous predictions of the amount of natural gas eventually found. But any estimate of reserves — however *405defined — on which a company relies in the course of its business is relevant to the company’s practices in estimating and reporting reserves.
We agree with the FTC that comparative information of this sort is “reasonably relevant” to its investigation. While, in response to the companies’ arguments, the FTC has advanced several examples to demonstrate the relevance of bid files,32 the Commission emphasized that this approach — which requires, in effect, the delineation of a particular theory of violation — is inappropriate in the pre-complaint stage; and here, too, we agree. While the FTC has not articulated the specific anti-competitive practices which may be present, it could not reasonably do so without access to the relevant documents.33 Certainly a wide range of investigation is necessary and appropriate where, as here, multifaceted activities are involved, and the precise character of possible violations cannot be known in advance.
3. The Superior Order
Apparently because Superior is not a member of the AGA and does not report proved reserve-estimates to the AGA, the district judge denied enforcement of Specifications G through J in relation to Superi- or. Again, this ruling misconceives the nature of and unduly limits the FTC’s investigation. Superior’s argument that it cannot be guilty of a conspiracy to underreport proved reserve estimates to the AGA is not dispositive, because the FTC’s investigation is not restricted to this theory. Superior does make reserve estimates for its fields in Southern Louisiana; therefore, it possesses information that could well be relevant to the FTC’s inquiry. In point of fact, comparison of Superior’s estimating process with that of a producer who does report to the AGA could be a useful analysis. At this stage, whether or not Superior has participated in some conduct that would amount to an unfair trade practice is certainly conjectural, but the Commission need not demonstrate that a complaint is likely to issue against Superior. We hold that the district judge erred in denying enforcement against Superior of major parts of the subpoena.
B. Application of Collateral Estoppel
The gas producers contended in the district court that, because the FPC determined in So La II that the AGA proved *406reserve data were accurate, the FTC is precluded from relitigating that issue by the principle of collateral estoppel.34 Further, as we noted in our analysis of the district court’s relevancy findings, the producers maintained that accuracy of the AGA’s proved reserve estimates is all that the FTC is really trying to investigate.
On appeal there is some disagreement among the producers as to whether the district court applied a collateral estoppel theory in modifying the FTC’s subpoenas. One group states that the district court “properly applied” collateral estoppel in its ruling;35 another company, however, claims that collateral estoppel “is not properly an issue in this case,”36 and still another professes indifference on the ground that it is not affected by the dispute.37
This confusion results from the district court’s order, which did not detail findings of fact and conclusions of law. It is reasonably clear, nonetheless, that th"e district judge employed a variety of collateral estoppel to restrict the FTC’s investigation. The order stated that the subpoenas were “improper insofar as they seek data for the purposes of enabling the Trade Commission to attempt to determine natural gas reserves of the validity or accuracy of natural gas reserve estimates, matters already considered and ruled upon by the Federal Power Commission . ” (emphasis added). In relation to the modifications of Specifications, G, H, and I, the court emphasized that all production under these specifications was to be made “for the sole purpose of permitting the Trade Commission to investigate whether there is a conspiracy in the reporting of natural gas proved reserve estimates, and not for the purpose of permitting the Trade Commission to investigate or determine the amount of proved natural gas reserves.” Thus, so far as we can tell, the district judge accepted the producers’ theory that in essence the FTC was investigating only a conspiracy to underreport proved reserves to the AGA. While the court professed to acknowledge the FTC’s right to determine “whether there exists any evidence of conspiracy in the reporting of [such estimates] to the American Gas Association,” the court required the FTC to take as a “given” the accuracy of the AGA data.
Although, as we have discussed, the FTC’s investigation is not focused exclusively on a mere recalculation of proved reserve estimates, the district court specifically precluded any FTC inquiry which would “determine” or even “investigate” the amount of such reserves. Such a restriction patently hamstrings the FTC’s effort to compare various estimates made by the producers and necessitates constant vigilance by the Commission as to whether it has overstepped the bounds delineated by the court. Equally important, the district court’s constriction of the FTC’s purpose, to determine only the possibility of a conspiracy in the reporting of proved reserves to the AGA, when coupled with the premise that the reliability of the proved reserve data had been conclusively established by the FPC, resulted in the exclusion on relevancy grounds of all data not relating to proved estimates.
We have already determined that all of the data requested by the FTC is reasonably relevant to its inquiry. Given that assumption, the question remains whether the FPC’s conclusions in a rate-making proceeding can foreshorten the FTC’s investigation; that is, whether the FTC can be collaterally estopped from investigating the “amount of proved natural gas reserves.” We conclude that collateral *407estoppel cannot be invoked to limit enforcement of the FTC’s subpoenas.
As a general rule, substantive issues which may be raised in defense against an administrative complaint are premature in an enforcement proceeding. The controlling case again is Endicott Johnson, where the Court stated that the petitioner had “advanced many matters that are entitled to hearing and consideration in its defense against the administrative complaint, but they are not of a kind that can be accepted as a defense against the subpoena.” 317 U.S. at 509, 63 S.Ct. at 343 (footnote omitted).38 Moreover, in holding that an administrative subpoena must be enforced if the information is relevant to a lawful purpose of the agency, and not unduly indefinite or unreasonably burdensome, the Supreme Court has clearly rejected other defenses. The reasons for this rule are obvious. If parties under investigation could contest substantive issues in an enforcement proceeding, when the agency lacks the information to establish its case, administrative investigations would be foreclosed or at least substantially delayed.39 As the Court stated in Oklahoma Press,
[Petitioners’ view, if accepted, would stop much if not all of investigation in the public interest at the threshold of inquiry and, in the case of the Administrator, is designed avowedly to do so. This would render substantially impossible his effective discharge of the duties of investigation and enforcement which Congress has placed upon him. 327 U.S. at 213, 66 S.Ct. at 508.
No substantive rights are negated by this restriction, for if a formal complaint is issued, subpoenaed parties may assert their defenses in the subsequent administrative proceeding. Further, the agency’s final decision in that adjudicatory proceeding is reviewable by a court of appeals.
These principles have consistently been applied when jurisdictional defenses have been raised in enforcement proceedings. Two recent cases are illustrative. In FMC v. Port of Seattle, the Ninth Circuit held that the district court erred in limiting enforcement of Maritime Commission discovery orders to only those facts necessary to determine the Commission’s jurisdiction to investigate the Port’s consolidation services and in refusing to permit the Commission to inquire into the “details” of the consolidation services. 521 F.2d 431, 433-436 (1975). Similarly, the Seventh Circuit held in SEC v. Savage that the Commission was not required to establish its jurisdiction by demonstrating that a company’s commodities future contracts were “securities” within the meaning of the Securities Act before the subpoena would be enforced. 513 F.2d 188, 189 (1975). The court emphasized that the company “would require SEC to answer at the outset of its investigation the possibly doubtful questions of fact and law that the investigation is designed and authorized to illuminate.” Id.40
While the defense of collateral estoppel is very much akin to these jurisdictional questions,41 it is, if anything, even *408more inappropriate in the investigatory context than questions of statutory coverage. Because a collateral estoppel defense rests on factual identities, an enforcing court to evaluate this defense must preview the ultimate complaint. In the instant case, the court must not only foretell the various theories which the FTC’s evidence might support and all issues which conceivably might be raised in a FTC proceeding, but must also define all issues decided by the FPC. The court then must determine if an issue decided in the first proceeding is identical to an issue to be decided in the second proceeding. Such an exercise is unwise, if not impossible, and is in clear violation of the Supreme Court’s admonition in Oklahoma Press that an agency’s inquiry should not be limited by “forecasts” of the “probable results.” 327 U.S. at 216, 66 S.Ct. 494.
That the enforcing court should not undercut the agency’s investigative function by such hypotheses has been recognized by other courts of appeal. The Sixth and Seventh Circuits recently enforced subpoenas issued by the FTC in an investigation of taxicab companies for possible violations of the FTC Act, despite claims of res judicata and collateral estoppel based upon prior Government actions brought under the Sherman Act. In FTC v. Markin, 532 F.2d 541 (6 Cir. 1976), the Sixth Circuit, analogizing to cases involving a question of agency coverage or jurisdiction, held that such defenses were premature in the enforcement proceeding:
Whether or not res judicata or collateral estoppel should be applied in this case depends on a variety of factual determinations which should be made by the Commission in the first instance .
The basic weakness in respondents’ position is that neither the district court nor FTC has sufficient information at the present time to make the factual findings required to resolve the principal issue of res judicata or collateral estoppel. The administrative proceeding should not be interrupted by judicial intrusion before the pertinent facts are determined and assessed by the Commission. Id. at 544.
The Seventh Circuit followed the same analysis in FTC v. Feldman, 532 F.2d 1092 (7th Cir. 1976). Noting that interpretation of the factual data sought by the FTC would involve agency expertise and discretion, and that the FTC undoubtedly would consider, among other things, the effect of the prior litigation in deciding whether or not to formulate a complaint, the court concluded:
We deem it the more appropriate and orderly procedure for the Commission to proceed with the investigation within its discretion. If it ultimately issues a complaint, appellants will then have an opportunity, depending on the issues raised by the complaint, or the proof thereunder, to assert the defense of res judicata or collateral estoppel, if they see fit. Id. at 1095.
In holding that collateral estoppel is not a proper defense to this enforcement proceeding,42 we do not reach the merits of the allegations that the FTC has intruded into the FPC’s territory of expertise43 and *409is attempting to relitigate an issue definitively settled by the Power Commission. We note, however, that this is an era of overlapping agency jurisdiction under different statutory mandates. In United States v. RCA, RCA contended that the Federal Communications Commission’s approval of a television station exchange collaterally estopped the Justice Department from attacking the exchange in a separate civil antitrust suit. 358 U.S. 334, 338-39, 79 S.Ct. 457, 3 L.Ed.2d 354 (1959). The Supreme Court held that collateral estoppel was inapplicable because the FCC has no power to decide antitrust questions: “the issue in controversy before the Commission was whether the exchange would serve the public interest, not whether § 1 of the Sherman Act had been violated.” Id. at 352, 79 S.Ct. at 468. Under the principles of RCA, what the FPC found to be consonant with the public interest could still be viewed by the FTC as an unfair method of competition. It therefore appears that a court should approach gingerly a claim that one agency has conclusively determined an issue later analyzed from another perspective by an agency with different substantive jurisdiction.
C. Burdensomeness Determinations
The FTC challenges the district court’s limitation of production under Specifications G, H, and I to a random sample of 100 fields out of approximately 220 in Southern Louisiana and to the years 1969 through 1971. The Commission also disputes the district court’s provision for production where the documents are located, rather than at FTC headquarters, at the option of the producer, with any reproduction costs to be borne by the FTC. These rulings ordinarily would seem to fall under the rubric of burdensomeness. In line with the Oklahoma Press requirement that the disclosure sought shall not be unreasonable, 327 U.S. at 208, 66 S.Ct. 494, the district court is authorized to impose reasonable conditions and restrictions with respect to the production of the subpoenaed material if the demand is unduly burdensome.44 It appears that such modifications rest within the discretion of the trial judge and should be reversed by a reviewing court only for an abuse of that discretion45 In this case, however, it is clear that determinations of burden were intimately tied to the district court’s constricted view of the FTC’s investigation; that is, the district court found the subpoenas to be unreasonably broad and burdensome because they were, in the court’s view, duplicative of FPC activities.46 *410Since these dispositions were colored in substantial measure by an erroneous concept of the FTC’s purpose, and rested at least in part on improper applications of collateral estoppel and relevance, we are not bound by an abuse of discretion standard47 and therefore review these modifications for mere error.48
We emphasize that the question is whether the demand is unduly burdensome or unreasonably broad. Some burden on subpoenaed parties is to be expected and is necessary in furtherance of the agency’s legitimate inquiry and the public interest. The burden of showing that the request is unreasonable is on the subpoenaed party.49 Further, that burden is not easily met where, as here, the agency inquiry is pursuant to a lawful purpose and the requested documents are relevant to that purpose.50 Broadness alone is not sufficient justification to refuse enforcement of a subpoena.51 Thus courts have refused to modify investigative subpoenas unless compliance threatens to unduly disrupt or seriously hinder normal operations of a business.52
There is no doubt that these subpoenas are broad in scope, but the FTC’s inquiry is a comprehensive one — and must be so to serve its purposes. Further, the breadth complained of is in large part attributable to the magnitude of the producers’ business operations. Although some of the producers have alleged that the time and expense involved in compliance with the subpoenas as presently drawn would be extreme,53 it is clear that clarification of some misunderstandings and limitation of some back-up data by the FTC staff have alleviated these concerns to some extent. Mobil Oil admits that the alleged burdensomeness of its subpoena was “substantially mitigated” during the course of extensive negotiations with *411Commission attorneys.54 Moreover, we cannot ignore the fact that those gas producers who complied with the subpoenas were able to submit the required data without undue effort.55
We turn now to the specific limitations at issue. The FTC maintains that the random sample limitation would seriously undermine its ability to compare the data supplied by producers who voluntarily complied with the subpoenas with the data from these producers. Comparison of the producers’ estimates with all data submitted to the AGA for this region also would be foreclosed to some extent. The Commission notes that other studies have utilized random sampling techniques and that, in its opinion, such studies are inadequate for its purposes. We are reluctant to approve such a limitation in light of the fact that the district court rested its restriction largely on collateral estoppel grounds.56 We therefore enforce the subpoena as originally conceived, without production on a random sample basis.
The district court’s limitation of Specifications G through I to the years 1969, 1970, and 1971 also cannot be sustained. The impetus for the FTC investigation was the drop in 1968 and 1969 of proved reserves as reported by the AGA. Clearly data from an earlier period would be necessary for comparative purposes. The Commission’s requirement of data beginning in 1962 is reinstated.57
The FTC argues that the producers’ option to release the documents for inspection where they are stored, when coupled with the FTC’s required assumption of any reproduction costs, is in derogation of the Commission’s subpoena power. We agree. The FTC is specifically authorized to compel production of evidence “from any place in the United States, at any designated place of hearing.”58 While room for accommodation and compromise is certainly available, the district court’s placement of the entire burden of travel and expense59 on the Commission was unwarranted on this record.60 We enforce the subpoena without this modification.
D. Confidentiality Protection
The district court imposed various conditions on the disclosure by the FTC of any documents designated as confidential by the producers. The producers are, of course, justifiably concerned about the confidentiality of these documents, some of which could be classified as trade secrets; however, the district court’s order goes too far in an effort to protect these valid interests.
In essence, the order requires that any release or use of the documents beyond the investigation first be cleared with the court. *412Thus, the Commission apparently could not use the documents in an adjudicatory proceeding without gaining the court’s permission. Nor could the Commission exercise its discretion to determine what documents are exempt from public disclosure under the FTC Act or the Commission’s rules.61 Although the FTC’s argument that the order would prohibit even the Commissioners from viewing the documents seems somewhat strained, the order would unquestionably place the court in a position of supervision and control over the Commission in the exercise of its statutory duties.
At least until the subpoenaed information has been made available to the agency and it has had an opportunity to rule on specific requests for confidential treatment, such a protective order is premature and improper. See FCC v. Schreiber, 381 U.S. 279, 290-1, 295-6, 85 S.Ct. 1459, 14 L.Ed.2d 383 (1965).62 Accordingly, we accept with some modifications, the FTC’s proposed confidentiality protection which would provide notice to the producers of any FTC decision. Specifically, we order that the FTC not disclose any of the documents produced which a company designates as confidential to any person63 outside the employ of the FTC (other than an outside consultant retained by the FTC who has agreed not to disclose the documents) without first giving the company ten days’ notice of its intention to do so.64 Such a *413procedure would, of course, provide an opportunity for judicial review at some later date, if the producers believe that a particular proposed disclosure is improper.
IV. CONCLUSION
Using its own conception of the proper scope of the FTC’s investigation, the district court limited the subpoena on a composite of relevance and collateral estoppel grounds. We have determined that these limitations, which effectively blocked legitimate avenues of the FTC’s inquiry, cannot be reconciled with the narrow ambit — as defined by the Supreme Court — of a court asked to enforce an agency’s investigative subpoena. We have also concluded that the district court erred in terms of other modifications founded on burdensomeness, and that certain confidentiality restrictions operated to usurp the agency’s initial decision-making power. We therefore enforce the subpoenas as issued by the FTC, with the exception of the two modifications, in regard to .raw field data and the suspected location of natural gas in currently unleased acreage, proposed by the FTC and accepted by the producers.65 We also charge the FTC with implementation of the modifications to Specifications G through K offered by the Commission but rejected by the producers as unacceptable for settlement purposes.66 Production is to be made within 90 days of the date of this opinion.67
So Ordered.
APPENDIX A
SUBPOENA DUCES TECUM
UNITED STATES OF AMERICA FEDERAL TRADE COMMISSION
To Mr. A. C. Long, Chairman Executive Committee & Chief Executive Officer,
Texaco, Inc., 135 East 42nd Street, New York, New York. 10017
You are hereby required to appear before Donald K. Tenney, an Attorney and Examiner of the Federal Trade Commission, at Room 368, Federal Trade Commission Building, 6th and Pennsylvania Avenue, N.W., in the City of Washington, D.C. 20580 on the 5th day of January, 1972, at 10:00 a. m., to testify in connection with the Commission’s investigation of various corporations and persons, File No. 711 0042, pursuant to Commission Resolution dated June 3, 1971, a copy of which is attached and made a part hereof, for the purposes stated therein.
And you are hereby required to bring with you and produce at said time and place the following books, papers, and documents; See attached “Definitions” and “Specifications.”
Fail not at your peril
*414In testimony whereof, the undersigned, an authorized official of the Federal Trade Commission, has hereunto set his hand and caused the seal of said Federal Trade Commission to be affixed at Washington, D.C., this 24th day of November, 1971.
[SEAL]
/s/_
Assistant Director, Bureau of Competition.
DEFINITIONS
As used herein, the term “documents” means all writings of every kind including books, records, folios, minutes, reports, memoranda, correspondence, agreements, discounted cash flow studies, cover sheets, calculation sheets, print outs, telegrams, diary entries, pamphlets, notes, charts, and tabulations in the possession, custody or control of the Company. The term “documents” also includes voice recordings and reproductions or film impressions of any of the aforementioned writings as well as copies of documents which are not identical duplicates of the originals and copies of documents of which the originals are not in the possession, custody or control of the Company. The term “documents” further includes all punch cards or other cards, tapes or recordings used in data processing, together with the programming instructions and other written material necessary to understand or use such punch cards, tapes or other recordings.
In response to specifications in which the term “documents” is followed by an asterisk (*), a verified written statement by an officer of the company containing the requested information may be submitted in lieu of the documents called for provided that the underlying documents or source materials are listed or otherwise specifically identified in, or as part of, such verified statement.
Each document submitted must be identified as to the specification or specifications to which it is responsive.
The term “the Company” means the corporation upon which this Subpoena was served as well as its directors, officers, employees, and agents; its subsidiaries and affiliates; and the directors, officers, employees and agents of its subsidiaries and affiliates. The term “the corporation” means the corporation upon which this Subpoena was served.
Unless otherwise stated, the following definitions apply to the specifications that ensue:
1. South Louisiana. That geographical area delineated by Map III, page 84, of the May, 1971 edition of Reserves of Crude Oil, Natural Gas Liquids, and Natural Gas in the United States and Canada and United States Productive Capacity as of December 31, 1970 including the offshore area. The term “Offshore South Louisiana” is defined as that geographic area which lies seaward from the Louisiana coastline. The South Louisiana Offshore Area is sometimes referred to as Federal Areas 1 through 4 and includes the West Cameron Area, East Cameron Area, Vermilion Area, South Marsh Island Area, Eugene Island Area, Shoal Area, South Pelto Area, Bay Marc-hand Area, South Timbalier Area, Grand Isle Area, West Delta Area, South Pass Area, Main Pass Area, Breton Sound Area, Chandeleur Area and Chandeleur Sound Area and any additions thereto, as indicated on the United States Geographical Survey “Oil and Gas Development Map of the Gulf Coast State of Louisiana Outer Continental Shelf”, as revised on January 5, 1971.
2. Net Production. The definition appearing in Technical Report No. 1, Standard Definitions for Petroleum Statistics (First Edition, July 1, 1969), at page 11, is adopted.
3. Natural Gas Present or Recoverable or Ultimately Recoverable.
a. Present. Natural gas in place, i. e., existing either in the gaseous phase or in solution with crude oil in a natural underground reservoir or reservoirs.
b. Recoverable. Natural gas in place that is producible.
*415c. Ultimately recoverable. Natural gas in place that is producible, together with its cumulative production.
4. Field. A field is an area consisting of a single reservoir or multiple reservoirs all grouped on, or related to, the same individual geological features and/or stratigraphical condition. A reservoir is a porous and permeable underground formation containing an individual and separate natural accumulation of hydrocarbons (oil and/or gas) which is confined by impermeable rock or water barriers and is characterized by a single natural pressure system.
5. Completion Date. The first date on which any permanent equipment for the production of oil or gas is installed in a well. Completion reports may relate to the abandonment of a well or to the installation of permanent productive equipment.
6 & 7. Associated Gas; Dissolved Gas. The definitions of these two terms that appear in Technical Report No. 1, Standard Definitions for Petroleum Statistics (First Edition, July 1, 1969), page 6, are adopted.
8. Nonassociated Gas. Natural gas which is in a reservoir or reservoirs not containing significant quantities of crude oil.
9-13. Proved Reserves; Revisions; Extensions; New Field Discoveries; and New Reservoir Discoveries in Old Fields. The definitions of these five terms that appear in Reserves of Crude Oil, Natural Gas Liquids, and Natural Gas in the United States and Canada and United States Productive Capacity as of December 31, 1970 at pages 102-104, are adopted.
14. Dedicated Reserves. The volume of natural gas committed to a pipeline company and for which both the seller and the pipeline company have received certificate authorization from the Federal Power Commission.
SPECIFICATIONS
A.Documents * which will indicate the correct legal name and business address of the corporation, its date and state of incorporation, and the name, position and home address of each officer and director of said corporation.
B. Documents * which will indicate the correct legal name and business address of the parent of the corporation, the date and state of incorporation of the parent and the percentage ownership the parent has in the corporation, and the name, position and home address of each officer and director of the parent.
C. The corporation’s Annual Reports for each of the years 1966, 1967, 1968, 1969 and 1970.
D. Documents * which will indicate the name and address of each subsidiary, affiliate, and division of the corporation and of the divisions of each such subsidiary and affiliate engaged in the exploration, development, production, or distribution of natural gas; the function(s) as heretofore set forth of each; and the dates and states of .incorporation and the names, positions, and addresses of officers, directors, managers of each subsidiary, affiliate, and division.
E. Documents * which will indicate (1) each type of customer purchasing natural gas, produced in South Louisiana, from the corporation, its subsidiaries and affiliates and (2) the manner and methods of distribution of such natural gas to each type of customer.
F. Documents * which will indicate the following for each of the years 1966 through 1970:
1. Total net production of natural gas, in units, in (a) the United States and (b) South Louisiana, by the corporation, its subsidiaries and affiliates.
2. Total unit and dollar volume of sales of the total net production of natural gas produced in (a) the United States and (b) South Louisiana, by the corporation, its subsidiaries and affiliates.
3. Total dollar volume of sales of the total net production of natural gas produced in South Louisiana by the corporation, its subsidiaries and affiliates to each type of customer identified in Specification E(l) — for 1969 and 1970 only.
*416G. Documents either received (from whatever source) or written by the Company, in whole or in part, at any time between January 1, 1962 to December 31, 1970, which contain estimates or evaluations of the volume of natural gas present or recoverable or ultimately recoverable (1) throughout all of South Louisiana (2) throughout all of Offshore South Louisiana and/or (3) in specific fields, portions of fields, leaseholds and/or portions of leaseholds located in Offshore South Louisiana.
Excluded from this specification are any documents previously made available to the Commission by the American Gas Association and'presently in the custody , of Price, Waterhouse & Company, 1801 K Street, Washington, D.C. Included in this specification by way of illustration but not limitation are documents containing estimates or evaluations including re-estimates or reevaluations made in connection with or in preparation for or as the result of the following: (1) bidding on or nominating leases (2) deciding whether to erect permanent platforms (3) compiling or inventorying total company reserves or supply (4) negotiating or contracting for the sale of natural gas, or for the joint or common exploration, development, production, purchase or sale of acreage, or for obtaining bank loans (5) filing depreciation expense schedules with Internal Revenue Service or (6) submitting field-by-field estimates to subcommittees or committees of the American Gas Association or the American Petroleum Institute.
H. Documents * indicating any or all of the following with regard to each field and leasehold in Offshore South Louisiana for which estimates or evaluations of the volume of natural gas, pertaining to the whole or a portion thereof, are produced pursuant to Specification G:
1.For each such field and portion thereof, its name and the number(s) of each block number comprising said field or portion thereof- — if the field or field portion is situated at least in part in a portion of a block, the portion of the block as well, e. g., “NW V-t”;
2. For each such leasehold and portion thereof, the OSC number and name(s) and location(s) of the field(s) and portion^) thereof comprising such leasehold or portion thereof;
3. The pipeline company(ies) serving each such field, leasehold, or portion thereof;
4. The producer(s) and the operator(s) of each such field, leasehold, or portion thereof, indicating the precise interest each such producer and operator has in the acreage;
5. For each such field, leasehold and portion thereof, the location (on the map) and designation of each well drilled including (for each such well):
a. ’ The current status as classified by the Company, e. g., “dry and abandoned”, “temporarily abandoned”, “suspended”, “shut-in”, “service”, “producer”, etc.;
b. Whether classified by the Company as an oil or gas well at the time of (1) application for drilling (2) the filing of each completion report (3) currently;
c. The number of reservoirs containing natural gas that have been penetrated by the well;
d. The date drilling commenced; the date total depth was reached; first date of testing; first date of testing officially reported; completion date; date commenced producing.
I. Documents either received (from whatever source) or written by the Company, in whole or in part, at any time subsequent to January 1, 1962, which refer, analyze, compare, comment on, set forth, and/or relate to any or all of the following:
1. Any natural gas estimates or evaluations called for by Specification G; the preparation or completion of such estimates or evaluations; the procedures, criteria or interpretations used in such preparation or completion; the identity of organizational units and personnel of the Company involved in such preparation or completion;
2. Any natural gas estimates or evaluations made available to the Commission by the American Gas Association and *417presently at Price, Waterhouse & Co., or appearing in any American Gas Association Report on Natural Reserves, published subsequent to January 1, 1967, including the constituent categories of these estimates such as “proved reserves”, “revisions”, “extensions”, “new field discoveries”, “new reservoir discoveries in old fields”; the preparation or completion of such estimates or evaluations; the procedures, criteria or interpretations used in such preparation or completion; the organizational units and personnel of the Company involved in such preparation or completion;
3. Any lease nominations and bids, any agreements for joint or common leasing, exploration, development, production, purchase or sale, or any cash flow or economic feasibility studies preparatory to leasing, exploring, developing, purchasing or selling, which involve Offshore South Louisiana acreage;
4. Any compilation, report or study of “dedicated reserves”;
5. Whether any well designated in response to Specification H — 5 contains natural gas in sufficient quantities as to be capable of producing in paying quantities.
J.Documents either received (from whatever source) or written by the Company, in whole or in part, at any time subsequent to January 1, 1966, which refer, analyze, compare, comment on, set forth, and/or relate to any or all of the following:
1. Any failures or delays, for whatever reason, in reporting proved reserves of natural gas to the American Gas Association, including any failures or delays by personnel of the Association to identify to subcommittee members all fields containing proved reserves;
2. The classification or exclusion or inclusion of volumes of natural gas as proved reserves;
3. The relationship between increases or decreases of crude oil proved reserves with increases or decreases of associated, dissolved or associated-dissolved natural gas proved reserves;
4.Negative revisions to American Gas Association proved reserve estimates because of clerical or mathematical error.
K. Documents either received (from whatever source) or written by the Company, in whole or in part, at any time subsequent to January 1, 1962, which refer, analyze, compare, comment on, set forth, and/or relate to any or all of the following:
1. The relation between the amount of “proved reserves” and the rate allowed, to be allowed, or that may be allowed for natural gas by the Federal Power Commission;
2. The reporting of lower “proved reserve” figures.
L. Documents * naming all employees of the corporation, its subsidiaries and affiliates who have, any time since January 1, 1966 with regard to Offshore South Louisiana, estimated, evaluated or enumerated natural gas proved reserves, dissolved gas proved reserves, potential gas supply or well drilling activity either for the American Gas Association, American Petroleum Institute, Potential Gas Committee, American Association of Petroleum Geologists or the International Oil Scouts, including local scout checks, indicating for each person named (1) the association for which he estimated or enumerated (2) whether a member of the association (3) what was estimated or enumerated and (4) the dates for which he estimated or enumerated for the particular association.
APPENDIX B
IN THE UNITED STATES DISTRICT COURT FOR THE DISTRICT OF COLUMBIA
Civil Action No. 1089-73 FEDERAL TRADE COMMISSION v.
TEXACO, INC.
*418Civil Action No. 1090-73 FEDERAL TRADE COMMISSION v.
STANDARD OIL CO. (INDIANA)
Civil Action No., 1092-73 FEDERAL TRADE COMMISSION v.
EXXON CORPORATION
Civil Action No. 1093-73 FEDERAL TRADE COMMISSION v.
SHELL OIL COMPANY
Civil Action No. 1095-73 FEDERAL TRADE COMMISSION v.
STANDARD OIL COMPANY OF CALIFORNIA
Civil Action No. 1096-73 FEDERAL TRADE COMMISSION v.
MOBIL OIL CORPORATION
ORDER
The Federal Trade Commission (“Trade Commission”) having petitioned on June 13, 1973, for enforcement of subpoenas duces tecum issued by an Assistant Director of the Trade Commission’s Bureau of Competition to each of the above captioned respondents on November 24, 1971, in the course of a Trade Commission investigation into natural gas reserve reporting procedures (FTC Investigation File No. 7110042); and the respondents having opposed enforcement of said subpoenas, contending that the principles of primary jurisdiction and collateral estoppel preclude the Trade Commission from seeking the demanded documents or data for purposes of determining the validity or accuracy of natural gas reserve estimates, and contending further, inter alia, that certain demands of the subpoenas are irrelevant to any proper subject or area of investigation and are unduly broad and burdensome; and the parties having fully briefed and presented oral argument on the issues; and the Court upon consideration of all the premises, being of the opinion that the Trade Commission is authorized to pursue the investigation to determine whether there exists any evidence of conspiracy in the reporting of proved natural gas reserve estimates to the American Gas Association by respondents, but that the subpoenas duces tecum are improper insofar as they seek data for the purposes of enabling the Trade Commission to attempt to determine natural gas reserves or the validity or accuracy of natural gas reserve estimates,- matters already considered and ruled upon by the Federal Power Commission, and the Court being of the further opinion that the subpoenas are improper in other respects as well and should not be enforced as issued:
It is now therefore ordered:
1. Enforcement of specifications A, B, C, D, E, and F of the subpoenas duces tecum is hereby granted. Enforcement of specifications G, H, I, J, K, and L is hereby denied except as provided below.
2. Respondents shall produce documents as called for by specifications G, H, and I of the subpoenas duces tecum for the years 1969, 1970 and 1971, subject to the following modifications and limitations:
(a) Production shall be limited to documents containing or underlying proved natural gas reserve estimates. Raw filed data, bid calculation data, and bid calculation files are not required to be produced. As regards underlying back-up data for each estimate called for by specification G, only the immediate data used to make the estimate need be submitted. For estimates arrived at volumetrically, *419specification 1(1) will be satisfied by supplying all the underlying numbers which were used in the formula including the recovery factor and the size of the reservoir (s). As for the estimates arrived at by pressure decline curves, specification 1(1) will be satisfied by submitting the curve used.
(b) Production of documents shall be made with respect only to a random sample of 100 of those offshore Southern Louisiana fields which were included in reports for 1971 by the Southern Louisiana Subcommittee of the American Gas Association Committee of Natural Gas Reserves. This random sample shall be selected by a procedure agreed upon between Trade Commission and respondents.
(c) Each respondent shall make production with respect to the fields, selected in the manner described in paragraph 2(b), in which it had an ownership interest as of the date reports were submitted by the Southern Louisiana Subcommittee of the American Gas Association Committee of Natural Gas Reserves.
(d) All production ordered pursuant to this paragraph 2 shall be made for the sole purpose of permitting the Trade Commission to investigate whether there is a conspiracy in the reporting of natural gas proved reserve estimates, and not for the purpose of permitting the Trade Commission to investigate or determine the amount of proved natural gas reserves.
3.Respondents shall produce documents as called for by specifications J and K of the subpoenas duces tecum, subject to the following modifications and limitations:
(a) Production shall be limited to documents relating to proved natural gas reserve estimates in those offshore Southern Louisiana fields which were included in reports for 1971 by the Southern Louisiana Subcommittee of the American Gas Association Committee of Natural Gas Reserves.
(b) Production shall be limited to documents prepared or dated during the years 1966 through 1971, inclusive, which were exchanged between or among, or constitute, contain or refer to any agreement, arrangement or communication between or among, respondent or others, including the American Gas Association.
4. Respondents shall produce documents as called for by specification L, except production shall be limited to the employees who have acted with respect to proved natural gas reserve estimates for offshore Southern Louisiana during the year 1966 through 1971, inclusive.
5. In complying with this Order, the definition of terms contained in the original subpoenas duces tecum shall apply.
6. Respondents shall comply with this Order within 180 days after the date upon which they are advised of the sample fields selected in accordance with paragraph 2(b) hereof.
7. Each respondent shall have the option of producing documents called for by this Order at the corporate office or field location where the responsive documents are normally maintained or at the Federal Trade Commission’s offices in Washington, D.C. With respect to documents as to which any respondent elects to make production at a corporate office or field location, the Trade Commission shall inspect and reproduce any of said documents at such office or field location at, such other location as agreed upon by the respective parties, and shall bear any costs of reproduction or copying which the Trade Commission may require or desire.
8. Any document produced under this Order which contains confidential information may be designated as being confidential by the respective respondents, in which event all documents so designated shall be subject to the following protective treatment:
(a) Documents designated as confidential by a respondent shall be deposited with and be maintained by a custodian who shall be the Secretary of the Commission. Unless and until otherwise ordered by the Court upon due notice to all affected parties documents so designated *420may be inspected only at the depository location and only by employees of the Trade Commission officially assigned to the Trade Commission’s investigation entitled “File No. 711 0042.” Said documents shall be used only in connection with said investigation, and said employees shall not suffer or permit disclosure or copying of any such document, or any portion thereof, or any information contained therein to any other person.
(b) Unless and until otherwise ordered by the Court upon due notice to all affected parties, documents designated confidential under this Order shall remain in custody of the Custodian and neither the documents nor any copies thereof shall be removed from such custody.
(c) At the conclusion of the Trade Commission’s investigation pursuant to which such confidential documents have been produced, all documents so designated as confidential, together with all copies thereof, shall be returned to the respective respondent unless the Trade Commission seeks and obtains an order of the Court providing otherwise.
(d) The protective provisions of this Order shall be deemed to apply to the Trade Commission, to the individual Commissioners of the Trade Commission and to all persons in the employ of the Trade Commission; sanctions for violation of any provision of this Order may be imposed on the Trade Commission, or any person who violates any provision of this Order.
9. The Court reserves its ruling as to any and all matters, contentions or issues not specifically disposed of by this Order. Jurisdiction over these proceedings is retained for the purposes of providing other and further relief as necessary.
So ordered this 22nd day of March, 1974.
/s/ George L. Hart Jr.
Chief Judge
APPENDIX C
IN THE UNITED STATES DISTRICT COURT FOR THE DISTRICT OF COLUMBIA
Civil Action No. 1091-73 FEDERAL TRADE COMMISSION v.
SUPERIOR OIL COMPANY ORDER
Upon consideration of the Federal Trade Commission’s petition for enforcement of a subpoena duces tecum, the matter having been fully briefed and argued before the Court, and the Court being advised in the premises, it is this 22nd day of March, 1974, ORDERED, That the respondent, The Superior Oil Co., Inc., shall comply, within 180 days from the date on which this Order becomes final, with Specifications A through F and K through L of the subpoena, provided that Specifications A, B. D. E and F may be complied with by submitting a verified written statement by an officer of the Company containing the requested information in lieu of the documents specified, and it is
FURTHER ORDERED, That as to the respondent, The Superior Oil Co., Inc., Specifications G through J of the subpoena be, and the same hereby are, denied enforcement and quashed; and it is
FURTHER ORDERED, That any document produced under this Order- which contains confidential information may be designated as being confidential by the respondent, in which event all documents so designated shall be subject to the following protective treatment:
(a) Documents designated as confidential by a respondent shall be deposited with and be maintained by a custodian who shall be the Secretary to the Commission. Unless and until otherwise ordered by the Court upon due notice to all affected parties documents so designated may be inspected only at the depository location and only by employees of the Trade Commission officially assigned to the Trade Commission’s investigation en*421titled “File No. 711 0042.” Said documents shall be used only in connection with said investigation, and said employees shall not suffer or permit disclosure or copying of any such document, or any portion thereof, or any information contained therein to any other person.
(b) Unless and until otherwise ordered by the Court upon due notice to all affected parties, documents designated confidential under this Order shall remain in custody of the Custodian and neither the documents nor any copies thereof shall be removed from such custody.
(c) At the conclusion of the Trade Commission’s investigation pursuant to which such confidential documents have been produced, all documents so designated as confidential, together with all copies thereof, shall be returned to the respondent unless the Trade Commission seeks and obtains an order of the Court providing otherwise.
(d) The protective provisions of this Order shall be deemed to apply to the Trade Commission, to the individual Commissioners of the Trade Commission and to all persons in the employ of the Trade Commission; sanctions for violation of any provision of this Order may be im-. posed on the Trade Commission, or any' person who violates any provision of this Order.
The Court reserves its ruling as to any and all matters, contentions or issues not specifically disposed of by this Order. Jurisdiction over these proceedings is retained for the purposes of providing other and further relief as necessary.
SO ORDERED THIS 22 DAY OF MARCH, 1974.
GEORGE L. HART, JR.
George L. Hart, Jr.
Chief Judge
. The FTC subpoena and the district court orders are reproduced in the appendix to this opinion.
. The term “proved reserves” is central to the discussion herein. The following definition has been adopted by the AGA:
Proved Reserves are the estimated quantity of natural gas which analysis of geologic and engineering data demonstrate with reasonable certainty to be recoverable in the future from known oil and gas reservoirs under existing economic and operating conditions. Reservoirs are considered proved that have demonstrated the ability to produce by either actual production or conclusive formation test.
The area of a reservoir considered proved is that portion delineated by drilling and defined by gas-oil, gas-water contacts or limited by the structural deformation or lenticularity of the reservoir. In the absence of fluid contacts, the lowest known structural occurrency of hydrocarbons controls the proved limits of the reservoir. The proved area of a reservoir may also include the adjoining portions not delineated by drilling but which can be evaluated as economically productive on the basis of geological and engineering data available at the time the estimate is made. Therefore, the reserves reported should include total proved reserves which may be in either the drilled or the undrilled portions of the field or reservoir. *395Natural gas reserves take into account the shrinkage of the reservoir gas volume resulting from the removal of the liquefiable portions of the hydrocarbon gases and the reduction of volume due to the exclusion of non-hydrocarbon gases where they occur in sufficient quantity to render the gas unmarketable.
The proved reserves estimated are to include all gas reserves regardless of size, availability of market, ultimate disposition or use.
See “Reserves of Crude Oil, Natural Gas Liquids, and Natural Gas in the United States and Canada and United States Productive Capacity,” Volume 28, June 1974. The first two paragraphs of this definition appear on page 103 of this publication, the third paragraph is derived from page 99, and the last paragraph is derived from pages 96 and 97.
Essentially the concept of proved reserves is bottomed on the presence of enough technical data to ensure reasonably accurate measurement of a known reservoir. Even proved reserves are only estimates, however, and competent evaluators may produce slightly different figures based on different analyses of the geological data. See, e. g., Federal Power Commission Staff Report on the Updated 31 Lease Investigation, June 1976, at 16; Federal Power Commission Analysis of “Gas Reserve Estimation of Offshore Producible Shut-in Leases in the Gulf of Mexico,” May 1976, at 1-3. Gas producers may also denominate reserves as “speculative,” “possible,” “probable,” “recoverable,” or “ultimately recoverable” — indicating the progression of knowledge as a field is developed — but there is no accepted use or definition of these terms by the industry. Only proved reserves are consistently defined, and only proved reserves are reported by the AGA.
. App. III 537a-543a, 556a-558a.
. 41 F.P.C. 378 (Mar. 20, 1969). The FPC order mandated an investigation of “offshore gas supply and costs associated therewith.” Id. at 379; see further discussion infra at 397-398 of 180 U.S.App.D.C., at 869-870 of 555 F.2d. In May of 1968 the Supreme Court had approved the FPC’s functional use of price “as a tool to encourage the production of appropriate supplies of natural gas.” Permian Basin Area Rate Cases, 390 U.S. 747, 796-98, 88 S.Ct. 1344, 1375, 20 L.Ed.2d 312.
. Mobil Oil Corp. v. FPC, 417 U.S. 283, 292-93, 94 S.Ct. 2328, 41 L.Ed.2d 72 (1974), citing Southern Louisiana Rate Cases, 428 F.2d 407, 418 (5th Cir. 1970). The area is defined by the FPC to include all parts of the state south of the thirty-first parallel, together with the offshore territory in the federal domain that would be bounded by Louisiana borders if extended into the Gulf of Mexico. Id.
. Section 5(a)(1) of the FTC Act, as amended, provides that “Unfair methods of competition in or affecting commerce, and unfair or deceptive acts or practices in or affecting commerce, are declared unlawful.” 15 U.S.C. § 45(a)(1).
. App. IX 1686a. Section 6(a) of the FTC Act, as amended, empowers the Commission
To gather and compile information concerning, and to investigate from time to time the organization, business, conduct, practices, and management of any person, partnership, or corporation engaged in or whose business affects commerce, excepting banks and common carriers subject to the Act to regulate commerce, and its relation to other persons, partnerships, and corporations. 15 U.S.C. § 46(a).
. App. Ill 497a.
. Section 9 of the FTC Act, as amended, provides in pertinent part:
For the purposes of [the FTC Act] the Commission, or its duly authorized agent or agents, shall at all reasonable times have access to, for the purpose of examination, and the right to copy any documentary evidence of any person, partnership, or corporation being investigated or proceeded against; and the Commission shall have power to require by subpoena the attendance and testimony of witnesses and the production of all such documentary evidence relating to any matter under investigation. Any member of the Commission may sign subpoenas, and members and examiners of the Commission may administer oaths and affirmations, examine witnesses, and receive evidence. Such attendance of witnesses, and the production of such documentary evidence, may be required from any place in the United States, at any designated place of hearing. 15 U.S.C. § 49.
. App. IV 625a, 643a.
. Section 9 of the FTC Act, as amended, provides in relevant part that
. in case of disobedience to a subpoena the Commission may invoke the aid of any court of the United States in requiring the attendance and testimony of witnesses and the production of documentary evidence. Any of the district courts of the United States within the jurisdiction of which such inquiry is carried on may, in case of contumacy or refusal to obey a subpoena issued to any person, partnership, or corporation issue an order requiring such person, partnership, or corporation to appear before the Commission, or to produce documentary evidence if so ordered, or to give evidence touching the matter in question; and any failure to obey such order of the court may be punished by such court as a contempt thereof. 15 U.S.C. § 49.
. Area Rate Proceeding (Southern Louisiana), 40 F.P.C. 530 (Sept. 25, 1968), modified on rehearing, 41 F.P.C. 301 (Mar. 20, 1969), aff’d, Southern Louisiana Area Rate Cases, 428 F.2d 407 (5th Cir.), cert. denied, 400 U.S. 950, 91 S.Ct. 241, 27 L.Ed.2d 257 (1970).
. 41 F.P.C. 378 (Mar. 20, 1969).
. 42 F.P.C. 1110 (Dec. 15, 1969).
. The FPC stated that evidence should be taken “with respect to the adequacy of gas supply and adequacy of service to consumers, the demand for gas, the cause of a gas shortage, if any, the effect of price on gas supply and demand, and other relevant economic evidence. . . .”42 F.P.C. 1110, 1112 (Dec. 15, 1969).
. 43 F.P.C. 444, 445 (Mar. 17, 1970). The FPC already had data pertaining to gas reserves from Form 15 reports filed by pipelines. Form 15 applies only to reserves “committed” or “dedicated” to interstate sale; thus, “uncommitted” reserves are unreported. The uncommitted reserves study was intended to supplement existing data in an effort to determine if the trends reflected in Form 15 reports were an accurate cross-check of AGA reported reserves. See 46 F.P.C. 86, 113-114 (July 16, 1976).
. Order and Opinion Determining Just and Reasonable Rates for Natural Gas Produced in the Southern Louisiana Area, 46 F.P.C. 86, 110-116 (July 16, 1971).
. Id. at 116. The Commission’s order was affirmed by the Fifth Circuit, Placid Oil v. FPC, 483 F.2d 880 (5th Cir. 1973), and the court of appeals subsequently was affirmed by the Supreme Court, Mobil Oil v. FPC, 417 U.S. 283, 94 S.Ct. 2328, 41 L.Ed.2d 72 (1974).
At the direction of Congress, the FPC began in 1971 a National Gas Reserves Study. The independent survey was conducted on a random sampling basis and produced estimates of gas reserves as of December 31, 1970. A staff report, published in May 1973, noted that the AGA total estimate was slightly higher than the NGRS total estimate. App. VI 1048a.
. Notably, the Fair Labor Standards Act incorporated sections 9 and 10 of the Federal Trade Commission Act for the purpose of any hearing or investigation. See 327 U.S. at 200, n. 24, 66 S.Ct. 494.
. The principles set down by the Supreme Court have been uniformly followed by the circuit courts of appeals. See, e. g., United States v. Litton Industries, 462 F.2d 14, 16 (9th Cir. 1972); Genuine Parts v. FTC, 445 F.2d 1382, 1391 (5th Cir. 1971); FTC v. Browning, 140 U.S.App.D.C. 292, 298, 435 F.2d 96, 102 (1970); SEC v. Wall Street Transcript Co., 422 F.2d 1371, 1375 (2d Cir.); cert. denied, 398 U.S. 958, 90 S.Ct. 2170, 26 L.Ed.2d 542 (1970); Adams v. FTC, 296 F.2d 861, 866 (8th Cir. 1961), cert. denied, 369 U.S. 864, 82 S.Ct. 1029, 8 L.Ed.2d 83 (1962).
. On the initial appeal to this court, Standard Oil of California maintained that the district court’s first order is not a final decision under 28 U.S.C. § 1291 and therefore is not appealable. This argument was rejected in the panel decision, and Standard Oil has not pressed it on rehearing en banc. We nonetheless note that it is settled that an order of a district court granting or denying an agency’s petition for enforcement of a subpoena is final and appealable. Ellis v. ICC, 237 U.S. 434, 442, 35 S.Ct. 645, 59 L.Ed. 1036 (1915); Int’l Brotherhood of Electrical Workers v. EEOC, 398 F.2d 248, 251 (3d Cir. 1968), cert. denied, 393 U.S. 1021, 89 S.Ct. 628, 21 L.Ed.2d 565 (1969). The district court’s retention of jurisdiction for possible further relief after the documents were produced does not defeat finality. See FTC v. Feldman, 532 F.2d 1092, 1098 (7th Cir. 1976).
. As previously discussed, the district judge did not concretely state the reasons for the limitation to proved reserves in his order. During the hearings, however, the district judge appeared to accept the producers’ arguments that only proved reserves are relevant. App. II 398a-402a, 431a, 439a-443a. The limitation to proved reserves was also premised in part on an application of collateral estoppel. See discussion infra at 409 of 180 U.S.App.D.C., at 881 of 555 F.2d.
.This standard was urged by the FTC in its first brief on appeal. FTC’s Brief at 16. In its supplementary brief the FTC argues that the pertinent inquiry is whether the requested material is “plainly irrelevant” to the investigation. Supp. Brief at 5, 31.
The “plainly irrelevant” language is derived, of course, from the Supreme Court’s statement in Endicott Johnson that the evidence sought by the subpoena was not “plainly incompetent or irrelevant” to any lawful purpose of the Secretary. 317 U.S. at 509, 63 S.Ct. 339. The issue before the Endicott Court was the authority of the district court to decide the question of statutory coverage; the appropriate standard of relevance was not directly addressed. In Oklahoma Press and Morton Salt, decided after Endicott, the Court spoke of information “relevant” and “reasonably relevant,” respectively, to the inquiry. 327 U.S. at 209, 66 S.Ct. 494; 338 U.S. at 652, 70 S.Ct. 357. More recently, the Court has stated that, for enforcement of an Internal Revenue Service summons for records, the Commissioner must demonstrate, in*402ter alia, that the inquiry “may be relevant” to a legitimate purpose. United States v. Powell, 379 U.S. 48, 57, 85 S.Ct. 248, 13 L.Ed.2d 112 (1964). And in See v. City of Seattle, 387 U.S. 541, 87 S.Ct. 1737, 18 L.Ed.2d 943 (1967), the Court noted, citing Morton Salt and Oklahoma Press, that when an administrative agency subpoenas corporate books or records, the subpoena must be “sufficiently limited in scope, relevant in purpose, and specific in directive so that compliance will not be unreasonably burdensome.” Id. at 544, 87 S.Ct. at 1740.
While some courts of appeal have employed a “clearly” irrelevant standard in enforcement proceedings, see, e. g., FTC v. Feldman, 532 F.2d 1092, 1098 (7th Cir. 1976); FTC v. Standard American, Inc., 306 F.2d 231, 235 (3d Cir. 1962), most have utilized the “reasonably relevant” language of Morton Salt. See cases cited at - of 180 U.S.App.D.C., n. 20, at 873 of 555 F.2d, n. 20. In Moore Business Forms v. FTC, 113 U.S.App.D.C. 231, 307 F.2d 188 (1962), a panel of this court stated it could not say that the subpoenaed information was “plainly irrelevant” to the charges in the complaint. Id. at 232, 307 F.2d at 189. Another panel of this court, however, has recited the “reasonably relevant” language. FTC v. Browning, supra n. 20, 140 U.S.App.D.C. at 298, 435 F.2d at 102.
Without deciding whether a “plainly irrelevant” standard actually is indicative of a more limited power of review, it suffices to dispose of this case that the material sought by the FTC is “reasonably relevant” to a permissible FTC purpose.
. See, e. g., Westside Ford v. United States, 206 F.2d 627, 632 (9th Cir. 1953); FTC v. Green, 252 F.Supp. 153, 156 (S.D.N.Y.1966).
. In Oklahoma Press, the Court emphasized that the purpose of the subpoena was “to discover and procure evidence, not to prove a pending charge or complaint, but upon which to make one if, in the Administrator’s judgment, the facts thus discovered should justify doing so.” 327 U.S. at 201, 66 S.Ct. at 501. And in Morton Salt the Court stated that “[ejven if one were to regard the request for information in this case as caused by nothing more than official curiosity, nevertheless law-enforcing agencies have a legitimate right to satisfy themselves that corporate behavior is consistent with the law and the public interest.” 338 U.S. at 652, 70 S.Ct. at 369.
. Supra, p. 396 of 180 U.S.App.D.C., at 868 of 555 F.2d. While the language of the resolution is broad, resolutions of this sort are not uncommon in the investigative process, and the agency was not required to articulate its purpose with greater specificity. See, e. g., FTC v. Feldman, supra n. 23, 532 F.2d at 1093; FTC v. Standard American, Inc., supra n. 23, 306 F.2d at 233-34; Westside Ford v. United States, supra n. 24, 206 F.2d at 630-31; FTC v. Green, supra n. 24, 252 F.Supp. at 154-56.
. FTC Reply Brief at 304; FTC Supp. Brief at 32-34, TR. at 5-7.
. Another entirely legitimate result may ensue from an investigation of questionable conduct, even if the agency should conclude that the conduct does not violate existing law — the in*404vestigation may reveal the need for changes in the law. The underlying act gives the FTC the authority to conduct investigations for the purpose of making recommendations to Congress. 15 U.S.C. § 49. See generally Davis, Administrative Law Treatise §§ 3.02-.03.
.The dissent argues that the evaluation of the relevance of particular documents is “essentially factual in nature,” and that the district court’s conclusion on this point can therefore be reviewed only for “clear error” or “abuse of discretion.” Dissenting op. at 425, 431, 434 of 180 U.S.App.D.C., at 897, 904, 907 of 555 F.2d. Here, however, the district court’s relevance determinations rested upon — and, indeed, were inseparable from — its view of the applicable law with respect to the proper scope of the FTC’s investigation.
When relevance determinations are, in essence, factual judgments, they are normally entitled to special deference from appellate courts, at least where there are issues of credibility of witnesses. We need not pause to consider to what extent the appellate court has greater latitude on review where, as here, the evidence was documentary, and raised no issues of credibility. Here the determinations of the trial court were dependent on, and integrally related to, a legal premise. In such a case, the appellate court has the authority — and the duty — to determine the proper legal premise and to correct the legal error of the trial judge, without limitation by the doctrines of “clearly erroneous” and “abuse of discretion” that are applicable to review of factual determinations. See Del. & Hudson Ry. Co. v. United Trans. Union, 146 U.S.App.D.C. 142, 159-160, 450 F.2d 603, 620-1, cert. denied, 403 U.S. 911, 91 S.Ct. 2209, 29 L.Ed.2d 689 (1971):
If the appellate court has a view as to the applicable legal principle that is different from that premised by the trial judge, it has a duty to apply the principle which it believes proper and sound. The reversal of the trial judge in no way reflects a determination that he was unreasonable or arbitrary, or chargeable with an abuse of discretion, but only and simply that his premise as to the applicable rule of law is deemed erroneous by the appellate court.
Id. See also Natural Resources Defense Council, Inc. v. Morton, 148 U.S.App.D.C. 5, 10, 458 F.2d 827, 832 (1972); Perry v. Perry, 88 U.S. App.D.C. 337, 190 F.2d 601 (1951); Societe Comptoir de L'Industrie v. Alexander's Dept. Stores, 299 F.2d 33, 35-6 (2d Cir. 1962); Milsen Co. v. Southland Corp., 454 F.2d 363, 369 (7th Cir. 1971).
. The district judge ruled from the bench that bid files are irrelevant to the FTC’s investigation. App. II 431a.
. Mobile Brief at 6. Bid files are considered highly confidential by the producers; a competitor who had access to the bidding model developed — at high cost — by another producer could easily outbid his opponent.
. The FTC suggests, for example, that bid files may contain proved reserve figures for adjacent tracts. These proved reserve figures could be compared with other proved reserve figures for the same tract maintained by the company. While Mobil asserts that none of its bid files contain such proved reserve figures, Mobil Brief at 17-18, the affidavit of a Commission attorney who has examined bid files of producers who complied with the subpoenas states that such files have been found to contain proved reserve estimates, App. IV 633a. On this record we cannot conclude that the Commission’s supposition is obviously wrong.
Moreover, the Commission suggests that bid files might be relevant in analyzing whether companies have deferred drilling in some circumstances in order to minimize the extent of proved reserves which would have to be reported. The district judge provided that if the FTC found a “situation where a company has been awarded a bid on a property and has delayed an unreasonable time in drilling on it so they could come up with a proper estimate, then you may apply and I will consider giving you the bid file on that particular one.” App. II 431a. Without the bid files, however, it may be difficult, if not impossible, for the FTC to identify such instances.
The Commission also suggests that bid files could be used to establish lease histories; such histories would enable the Commission to examine the relationship, if any between “speculative” and “proved” estimates. If the Commission were to find a reasonably stable relationship between these different estimates — if, for example, “speculative” estimates were consistently higher than the reported “proved” estimates, and by a roughly equivalent amount— this might well be indicative of anticompetitive practices.
. In Moore Business Forms v. FTC, supra, n. 23, the company argued against enforcement on the ground that the documents sought were not relevant — indeed, were “meaningless” — to the precise theory the Government would have to use to demonstrate a trade violation. 113 U.S.App.D.C. at 232, 307 F.2d at 189. A panel of this court enforced the subpoenas per curiam, noting that the Commission had not yet ruled on the inherent factual question and that the court should not “anticipate” the Commission’s determination by passing on that question. Id.
.In addition, the producers argued that the doctrine of “primary jurisdiction” forecloses this issue to the FTC, since regulatory and fact-finding expertise concerning proved reserve estimates lies with the Power Commission. On appeal, and particularly on rehearing en banc, the producers have concentrated on collateral estoppel, rather than on a primary jurisdiction argument, presumably because the district court’s order appears more likely to be premised on collateral estoppel.
. Texaco, et al. Supp. Brief at 2.
. Standard Oil (California) Supp. Brief at 2.
. Superior Supp. Brief at 2.
.While the defenses urged were briefly summarized by the Court in a footnote, see 317 U.S. at 509 n. 11, 63 S.Ct. at 343 n. 11, they were explained in greater (and here quite pertinent) detail in the Second Circuit’s decision:
Defendants also urge that application of the Walsh-Healy Act to their tanneries, etc., would be improper because of an alleged prior inconsistent “ruling” made, as to a different company, by the acting administrator, and because of certain conduct thought to “estop” the government. Consideration of these issues has no place in such a proceeding as this . . . . Perkins v. Endicott Johnson Corp., 2 Cir., 128 F.2d 208, 224, aff’d, 317 U.S. 501, 63 S.Ct. 339, 87 L.Ed. 424.
. The instant case is an ample witness to the correctness of this rationale. Enforcement proceedings began in 1973.
. See also SEC v. Brigadoon Scotch Distributing Co., 480 F.2d 1047, 1052-53 (2d Cir. 1973), cert. denied, 415 U.S. 915, 94 S.Ct. 1410, 39 L.Ed.2d 469 (1974); FTC v. Gibson, 460 F.2d 605, 608 (5th Cir. 1972).
. The producers specifically argued that the FTC had no “jurisdiction” to inquire into gas reserves, by virtue of both primary jurisdiction and collateral estoppel. App. II 218-220a, 226a. In the second hearing in the district court, the parties agreed to present their “jurisdictional” arguments first. Id. 331a-332a.
. We do not hold that collateral estoppel can never be raised in defense to an investigative subpoena. Instances of abuse of a court’s process can be imagined, though they are unlikely. In the instant case, we can perceive no reason to deviate from the general principles discussed above. Moreover, because we conclude that the assertion of collateral estoppel in this enforcement proceeding is premature, we need not reach the issue, discussed in Judge Leventhal’s concurring opinion, of whether a determination in an essentially legislative rate-making proceeding can ever be given preclusive effect.
. In this context we note that section 15(b) of the Federal Energy Administration Act of 1974, P.L. 93-275, 88 Stat. 96, 109 (May 7, 1974), provides:
(b) Not later than one year after the effective date of this Act, the Administrator shall submit a report to the President and Congress which will provide a complete and independent analysis of actual oil and gas reserves and resources in the United States and its Outer Continental Shelf, as well as of the existing productive capacity and the extent to which such capacity could be increased for crude oil and each major petroleum product each year for the next ten years through full utilization of available technology and capacity. The report shall also contain the Admin*409istration’s recommendations for improving the utilization and effectiveness of Federal energy data and its manner of collection. The data collection and analysis portion of this report shall be prepared by the Federal Trade Commission for the Administration. Unless specifically prohibited by law, all Federal agencies shall make available estimates, statistics, data and other information in their files which, in the judgment of the Commission or Administration, are necessary for the purposes of this subsection.
Although this statute was enacted several years after the FTC commenced its investigation, it is at least indicative that Congress intends a major role for the FTC in the analysis of natural gas reserves.
. Adams v. FTC, supra n. 20, 296 F.2d at 870 n. 7; see SEC v. Savage, 513 F.2d 188, 189 (7th Cir. 1975); SEC v. Brigadoon Scotch Distributing Co., supra n. 40, 480 F.2d at 1056; Genuine Parts Co. v. FTC, 313 F.Supp. 855, 857 (N.D. Ga.1970), aff'd, 445 F.2d 1382 (5th Cir. 1971).
. See FTC v. Lonning, 176 U.S.App.D.C. 200, at 209, 539 F.2d 202, at 211, 1976; FCC v. Cohn, 154 F.Supp. 899, 912 (S.D.N.Y.1957); cf. NLRB v. Northern Trust Co., 148 F.2d 24, 29 (7th Cir.), cert. denied, 326 U.S. 731, 66 S.Ct. 38, 90 L.Ed. 435 (1945). Most courts have not enunciated the correct scope of review. In Adams v. FTC, supra n. 20, for example, a panel of the Eighth Circuit overturned several modifications made by the district court on grounds of burdensomeness without specifically stating the applicable standard. See 296 F.2d at 867-870.
.That many of the restrictions were premised on a limited view of the FTC’s inquiry is evident from the district judge’s remarks towards the close of the second hearing:
Well, Gentlemen, I think this: it is within their province to determine whether there has been any violation of the matters that are entrusted to them. For that I don’t think it is necessary or proper that they endeavor to obtain and to determine the entire gas reserves available to all these companies, but it may well be pertinent that they get certain *410information to determine whether or not there has been a conspiracy to get together and violate some law in connection with these returns.
So I think the better way to handle it would be for the Court to limit their discovery in such a manner as to cover the purposes and not go to all out to have a further determination of what the national gas reserve is.
Now, how do we approach that? Your present subpoenas are certainly, it seems to me, too broad .
App. II 397a.
In formulating the random sample limitation, the court stated,
Say 100 out of 220, would give them, it seems to me, ample opportunity to prove any conspiracy if there is one. At the same time, it wouldn’t let them get into the business of estimating all the gas reserves in the country.
App. II 438a.
. Cf. Colonial Times v. Gasch, 166 U.S.App. D.C. 184, 189-191, 509 F.2d 517, 522-24 (1975); Societe Comptoir de LTndustrie Cotonniere Establissements Boussac v. Alexander’s Department Stores, Inc., 299 F.2d 33, 35-36 (2d Cir. 1962); Ring v. Spina, 148 F.2d 647, 650 (2d Cir. 1945).
. Arguably, these questions could be remanded to the district court for a reassessment, free from the errors made in the areas of collateral estoppel and relevance. This litigation already has been inordinately delayed, however; a proceeding usually summary in nature has stretched into years. In a protracted litigation of this sort, we need not return an issue “for another round of proceedings in the trial or appellate courts” — even if that issue is one which normally depends on trial court discretion — “if we can fairly dispose of it at this juncture.” Zenith Radio Corp. v. Hazeitine Research, 401 U.S. 321, 340-41, 91 S.Ct. 795, 807, 28 L.Ed.2d 77 (1971).
. See United States v. Powell, 379 U.S. 48, 58, 85 S.Ct. 248, 13 L.Ed.2d 112 (1964); FTC v. Standard American, Inc., supra n. 23, 306 F.2d at 235.
. See 379 U.S. at 58, 985 S.Ct. 248; SEC v. Brigadoon Scotch Distributing Co., supra n. 40, 480 F.2d at 1056; Genuine Parts Co. v. FTC, supra n. 44, 445 F.2d at 1391; Adams v. FTC, supra n. 20, 296 F.2d at 867; FCC v. Cohn, supra n. 45, 154 F.Supp. at 912.
. Adams v. FTC, supra n. 20, 296 F.2d at 867. The Fifth Circuit has stated that the Commission must be accorded “extreme breadth” in conducting its investigations. Genuine Parts Co. v. FTC, supra n. 44, 445 F.2d at 1382, citing United States v. Morton Salt, 338 U.S. at 652, 70 S.Ct. 357.
. See, e. g., SEC v. Savage, supra n. 44, 513 F.2d at 189; SEC v. Wall Street Transcript Corp., supra n. 20, 422 F.2d at 1381; FTC v. Standard American, Inc., supra n. 23, 306 F.2d. at 235.
. See, e. g., App. IX 1759a-1762a.
. Mobil Brief at 5; see App. XI 2014a-2031a.
. See FTC Brief at 52-53; App. IV 628a. Gulf Oil, a company with extensive natural gas operations, informed the Commission that 2028 man-hours were spent gathering the documents. Two other companies compiled, reproduced, and forwarded the data to the FTC within three months. Id.
. See note 46 supra.
. The district court also changed the beginning date in Specification K from 1962 to 1966. This modification must fall for the same reason.
. 15 U.S.C. § 49; see n. 9 supra. While this statute grants the FTC the power of “access” and the “right to copy” any documentary evidence of an entity under investigation, it also enables the FTC to require such evidence via a subpoena duces tecum. See id. Here the FTC chose to act pursuant to its subpoena power, not its access power.
. This is not a case in which the subpoena is directed to a third party not under investigation. See FTC v. Bowman, 149 F.Supp. 624, 630 (N.D.Ill.), aff'd, 248 F.2d 456 (7th Cir. 1957). Cf. United States v. Friedman, 3rd Cir., 532 F.2d 928 (1976); United States v. Davey, 426 F.2d 842 (2d Cir. 1970); United States v. Dauphin Deposit Trust Co., 385 F.2d 129 (3d Cir. 1967), cert. denied, 390 U.S. 921, 88 S.Ct. 854, 19 L.Ed.2d 981 (1968).
. There is no indication that the bulk of these documents are in current business use; in fact, since the investigation is focused on the period 1962-1971, the situation appears to the contrary. See, e. g., App. IX 1762a. See also FTC v. Standard American, Inc., supra n. 23, 306 F.2d at 235.
. See 15 U.S.C. § 46(f); 16 C.F.R. §§ 3.45, 4.10, 4.11.
. In the past, some courts have conditioned enforcement of an agency subpoena upon a protective order. See, e. g., FTC v. Menzies, 145 F.Supp. 164 (D.Md.1956), aff’d, 242 F.2d 81 (4th Cir.), cert. denied, 353 U.S. 957, 77 S.Ct. 863, 1 L.Ed.2d 908 (1957); FCC v. Cohn, supra n. 45, 154 F.Supp. at 912-913. The Schreiber decision makes clear, however, that it is the agencies, not the courts, which should, in the first instance, establish the procedures for safeguarding confidentiality. See 381 U.S. 295-6, 85 S.Ct. 1459. See also FTC v. United States Pipe and Foundry Co., 304 F.Supp. 1254, 1260 (D.D.C.1969), FTC v. Green, supra n. 24, 252 F.Supp. at 157; Gellhorn, “The Treatment of Confidential Information by the Federal Trade Commission: Pretrial Practices,” 36 U.Chi.L. Rev. 113, 126 (1968).
. We think it not unreasonable to require notice to the producers even in the event of a proposed release to Congress, since the circumstances surrounding such a disclosure cannot presently be ascertained. See Ashland Oil v. FTC, 179 U.S.App.D.C. 22, 548 F.2d 977 (1976).
. The Court is not herein adopting a rule of general applicability for a 10-day notice provision. It is rather adopting for purposes of this case a proposal for confidentiality advanced by FTC, even though this was put as a basis for settlement and no settlement was reached.
It should be noted that the settlement conference was initiated by this Court. Pursuant to an order of this Court dated April 21, 1976, counsel for the FTC and the appellees conferred for the purpose of seeking agreement as to the issues which still divided them on this appeal. On May 19, 1976, the FTC and Superi- or filed a Stipulation with the Court, indicating that they were “unable to agree on any modifications of the district court’s order of March 22, 1974, concerning Superior which would eliminate or narrow the issues remaining for decision by this Court.” On the same date, the FTC and the other six appellees who are parties in this matter filed a “Stipulation re Issues on which Parties have Agreed and Issues which Remain to be Resolved by the Court,” in which they set forth certain issues upon which they had reached agreement. Attached to the stipulations was a document entitled “FTC’s Statement of Issues and Proposed Modifications,” which included certain “modifications the FTC is willing to accept but which the Companies have not agreed to.” Paragraph 18 of this latter document (Paragraph 9 of the Attachment to the “Stipulation” filed with Superior), which sets forth the modifications of the district court’s confidentiality protection that the FTC was “willing to accept,” reads as follows:
Subject to the exceptions set forth below, the FTC will not disclose any of the documents produced which a company designates confidential to any person outside the employ of the FTC (other than an outside consultant retained by the FTC who has agreed not to disclose the documents) without first giving the company ten days’ notice of its intention to do so.
(a) With respect to an official request for such documents from a committee or subcommittee of Congress or a court (by compulsory process), the FTC will advise the Congressional committee or subcommittee or the court that the company considers the material to be confidential, and will give the company ten days’ prior notice where possible, and in any event, as much advance notice as can reasonably be given, before releasing or granting access to the documents, [footnote omitted]
*413(b) The above notice provisions shall not apply to any information which (1) is now in the public domain; (2) enters the public domain from a source other than the FTC or its employees; (3) was in the FTC’s possession prior to disclosure to the FTC by Superior; or (4) is supplied to the FTC or its employees by a third party lawfully in possession thereof.
(c) In the event that the investigation with respect to which the subpoena issued results in issuance of an adjudicative complaint, the confidential status of the documents and the limitations on their disclosure shall be governed solely by the applicable provisions of the FTC’s Rules of Practice, Part 3 — Rules of Practice for Adjudicative Proceedings.
.Stipulation re Issues on Which Parties Have Agreed and Issues Which Remain to Be Resolved by the Court, May 19, 1976, at 5.
. Id. at 7-9, ¶ 15-17; FTC’s Statement of Issues and Proposed Modifications (re Superior Oil), May 19, 1976, at 3-5, ¶ 5-8.
. The district court ordered that the documents be produced within 180 days. However, the experience of those companies that have already complied with the subpoenas- — evidence which was, of course, not available to the district court — indicates that 90 days should suffice. See notes 54 and 55 supra and accompanying text. To remand this issue to the district court for re-evaluation in light of this new evidence would only prolong this already protracted litigation unnecessarily. See note 48 supra.