CHURCH OF SCIENTOLOGY OF CALIFORNIA, Appellant,
                                       v.
                        INTERNAL REVENUE SERVICE, et al.
                                  No. 83-1856.
                         United States Court of Appeals,
                          District of Columbia Circuit.
                             Argued April 11, 1984.
                              Decided May 27, 1986.
                            As Amended May 27, 1986.
  Church brought action under Freedom of Information Act to compel Internal
 Revenue Service to disclose all documents in its possession relating to
 church.  The United States District Court for the District of Columbia, Norma
 Holloway Johnson, J., 569 F.Supp. 1165, entered summary judgment in favor
 of IRS, and church appealed.  The Court of Appeals, Scalia, Circuit Judge,
 held that:  (1) statute governing IRS disclosure of tax return information did
 not supersede FOIA;  (2) IRS was not required to search files of all regional
 and district offices;  and (3) IRS should not have restricted its search to
 records relating only to California branch of church.
  Vacated and remanded.

 [1] RECORDS
 Statute governing Internal Revenue Service disclosure of tax return information
 did not supersede Freedom of Information Act, but merely gave rise to exemption
 under Act, and IRS was still required to conform to FOIA procedures in
 asserting any exemption;  disagreeing with White v. IRS, 707 F.2d 897 (6th
 Cir.);  King v. IRS, 688 F.2d 488 (7th Cir.);  and Zale Corp. v. IRS, 481
 F.Supp. 486 (D.D.C.).  5 U.S.C.A. s 552(b)(3);  26 U.S.C.A. s 6103.

 [2] RECORDS
 Internal Revenue Service was not required to search files of all of its
 regional and district offices in response to church's Freedom of Information
 Act request;  church had made its request to national office, and, under IRS
 regulations, IRS was only required to search files of that office, though it
 went further and searched files of two field offices particularly pertinent to
 church's operations.  5 U.S.C.A. s 552(a)(3)(B).

 [3] RECORDS
 In responding to church's request to disclose all documents relevant to church,
 Internal Revenue Service could restrict its document search to files whose
 subjects indicated connection with church, and was not further required to
 search through every file in its possession to see if reference to church
 appeared somewhere in it.  5 U.S.C.A. s 552(a)(3).

 [4] RECORDS
 Internal Revenue Service's mere generalized assertion that it had examined
 appropriate subject files in response to church's Freedom of Information Act
 request was insufficient to show compliance with Act;  IRS was required to file
 affidavit reciting facts enabling court to satisfy itself that appropriate
 files had been searched and that further search would be unreasonably
 burdensome.  5 U.S.C.A. s 552(a)(4)(B).

 [5] RECORDS
 Mere deletion by Internal Revenue Service of identifying material would not
 cause tax return information to lose its statutorily protected status, and
 thus, IRS was not required to make document-by-document examination, in
 response to church's Freedom of Information Act request, to determine
 possibility of redaction for that purpose.  5 U.S.C.A. s 552(b);  26
 U.S.C.A. s 6103.

 [5] RECORDS
 Mere deletion by Internal Revenue Service of identifying material would not
 cause tax return information to lose its statutorily protected status, and
 thus, IRS was not required to make document-by-document examination, in
 response to church's Freedom of Information Act request, to determine
 possibility of redaction for that purpose.  5 U.S.C.A. s 552(b);  26
 U.S.C.A. s 6103.

 [6] RECORDS
 Internal Revenue Service's search for only records relating to California
 branch of church was not adequate response to Freedom of Information Act
 request made by California branch of church;  church had sought information
 relating to other branches of church, and IRS did not establish that files
 relating to other branches would only contain statutorily protected tax
 return information.  5 U.S.C.A. s 552(b);  26 U.S.C.A. s 6103.

 [7] RECORDS
 When claimed Freedom of Information Act exemption consists of generic
 exclusion, dependent upon category of records rather than subject matter which
 each individual record contains, resort to Vaughn index is futile and not
 required.  5 U.S.C.A. s 551 et seq.

 [8] RECORDS
 While in camera, individual inspection of each of small number of documents
 without detailed public affidavits and Vaughn indices is sometimes
 acceptable in determining adequacy of response to Freedom of Information Act
 request, that approach cannot be applied to large numbers of documents,
 especially if they represent only sampling;  in such cases, court must require
 agency to sustain its burden of proving that documents it sought to withhold
 were exempt from disclosure by appropriate combination of detailed public
 affidavits and, if necessary, indices, resorting to in camera examination of
 documents and affidavits only where these prove inadequate.  5 U.S.C.A. s
 551 et seq.

 [8] RECORDS
 While in camera, individual inspection of each of small number of documents
 without detailed public affidavits and Vaughn indices is sometimes
 acceptable in determining adequacy of response to Freedom of Information Act
 request, that approach cannot be applied to large numbers of documents,
 especially if they represent only sampling;  in such cases, court must require
 agency to sustain its burden of proving that documents it sought to withhold
 were exempt from disclosure by appropriate combination of detailed public
 affidavits and, if necessary, indices, resorting to in camera examination of
 documents and affidavits only where these prove inadequate.  5 U.S.C.A. s
 551 et seq.

 [8] RECORDS
 While in camera, individual inspection of each of small number of documents
 without detailed public affidavits and Vaughn indices is sometimes
 acceptable in determining adequacy of response to Freedom of Information Act
 request, that approach cannot be applied to large numbers of documents,
 especially if they represent only sampling;  in such cases, court must require
 agency to sustain its burden of proving that documents it sought to withhold
 were exempt from disclosure by appropriate combination of detailed public
 affidavits and, if necessary, indices, resorting to in camera examination of
 documents and affidavits only where these prove inadequate.  5 U.S.C.A. s
 551 et seq.
  *147 **79 Appeal from the United States District Court for the District
 of Columbia (Civil Action No. 80-03239).
  Robert A. Seefried, Washington, D.C., for appellant.
  Richard Wyndon Perkins, Atty., Dept. of Justice, with whom Glenn L. Archer,
 Jr., Asst. Atty. Gen., Joseph E. diGenova, U.S. Atty., Michael L. Paup and
 Stephen Gray, Attys., Dept. of Justice, Washington, D.C., were on brief, for
 appellees.

  Before WRIGHT and SCALIA, Circuit Judges, and FRIEDMAN, [FN*] Circuit Judge of
 the United States Court of Appeals for the Federal Circuit.

      FN* Sitting by designation pursuant to 28 U.S.C. s 291(a).

  Opinion for the Court filed by Circuit Judge SCALIA.

  SCALIA, Circuit Judge:
  This case arises out of the efforts of the Church of Scientology of California
 to obtain documents from the Internal Revenue Service under the Freedom of
 Information Act, 5 U.S.C. s 552 (1982) ("FOIA").  It requires us to review
 the District Court's grant of summary judgment to the IRS on the adequacy of
 its response to the Church's FOIA request.  To do so we must consider, among
 other things, the relation between FOIA and the provisions of the Internal
 Revenue Code that govern disclosure of return information, 26 U.S.C. s 6103
 (1982).
                                        I
  On May 16, 1980 the Church sent a Freedom of Information request to the IRS.
 It comprises seven single-spaced typed pages and is extremely confused, but for
 purposes of this appeal it has been adequately summarized by the Church as
 essentially requesting:
   1. All documents or records "relating to or containing the names of
 Scientology, Church of Scientology, any specific Scientology church or entity
 identified by containing the words Scientology, Hubbard and/or Dianetics in
 their names, L. Ron Hubbard or Mary Sue Hubbard," which could be located in a
 number of systems of records or files specifically identified in the FOIA
 request, "including but not limited to those located at the National Office,
 Regional Offices, Service Centers, District offices or Local IRS offices."
   2. All documents generated, received or which otherwise came into the
 possession of the IRS subsequent to the preparation of an index in a tax case
 involving the Church of Scientology of California pending in the United States
 Tax Court, *148 **80 Church of Scientology of California v.
 Commissioner of IRS, 83 T.C. 381 (U.S.T.C.) [referred to below as the "Tax
 Court case"].
  Brief for Appellants at 1-2.
  The IRS's first response, dated July 22, 1980, requested additional time to
 "locate and consider releasing the Internal Revenue Service records to which
 you have requested access" and estimated that the Service would respond on
 August 29.  On September 17, 1980, a response still not having been received,
 the Church filed an appeal to the Commissioner.  After the IRS acknowledged but
 failed to respond to the appeal, the Church filed a complaint in the United
 States District Court for the District of Columbia on December 18, 1980 under
 5 U.S.C. s 552(a)(4)(B) (1982).  In January 1981 the IRS finally responded
 to the Church's request with a letter.  For the sake of simplicity, we will
 limit our summary of that response to those factors that have some bearing on
 the issues here.
  The IRS noted that it had limited the scope of the Church's request to
 documents pertaining to the California Church because the Church had not
 provided authorizations from any other Scientology entity nor from the
 Hubbards.  Geographically the Service had limited the search to the National
 Office, the Covington, Kentucky, office and the Los Angeles office.  The IRS
 claimed that all documents relating to the Tax Court case not previously
 released were exempt from disclosure under Section 6103(e)(7) because
 disclosure would seriously impair Federal tax administration.  It released in
 full some national office documents acquired subsequent to the Tax Court case
 index, but justified only partial release of other National Office documents on
 grounds that they were outside the scope of the appeal, that their disclosure
 would cause a clearly unwarranted invasion of privacy, see 5 U.S.C. s
 552(b)(6), or that they reflected return information of third parties, see
 26 U.S.C. s 6103(a).
  After the IRS answered the complaint, the Church moved for an order requiring
 the IRS to prepare a Vaughn index of the withheld documents, see Vaughn
 v. Rosen, 484 F.2d 820 (D.C.Cir.1973), but the District Court denied the
 motion.  Instead it ordered submission for in camera inspection of:  (1)
 twenty-six documents located in the National Office which contained portions
 alleged to be exempt under 5 U.S.C. s 552(b)(6) because their disclosure
 would constitute an unwarranted invasion of personal privacy;  (2) three
 documents located at the National Office for which exemption was claimed under
 Section 6103(e)(7) because their disclosure would impair federal tax
 administration;  and (3) all documents generated in connection with the Tax
 Court case. [FN1]  After in camera inspection of some 5,600 pages of documents,
 the District Court granted the IRS's motion for summary judgment and dismissed
 the action with prejudice in June 1983.  The Church appealed.  We have
 jurisdiction under 28 U.S.C. s 1291 (1982).

      FN1. In its opinion, Church of Scientology of California v. IRS, 569
     F.Supp. 1165, 1171-72 (D.D.C. June 24, 1983), the court speaks of eight
     documents parts of which were withheld under the personal privacy
     exception, three documents parts of which were withheld because they dealt
     with third-party return information, and four documents parts of which were
     withheld because they were outside the scope of the plaintiff's request.
     The record does not explain the discrepancies between the number and type
     of documents ordered lodged in camera and the number and type of documents
     discussed in the court's opinion;  but those discrepancies are not
     important for our disposition of this case.

                                         II
  [1] The first issue we must address is the relation between FOIA and
 Section 6103.  The Church argues that Section 6103 gives rise to an
 exemption from disclosure only under FOIA Exemption 3, 5 U.S.C. s 552(b)(3),
 and subject to the procedural provisions of FOIA, including its de novo review
 requirement.  The IRS urges us to affirm the District Court's holding that
 Section 6103 totally supersedes FOIA and provides the exclusive criteria for
 release of records affected by that section, so that courts must uphold any IRS
 refusal to *149 **81 disclose under Section 6103 that is not arbitrary
 or capricious and does not violate the other provisions of the Administrative
 Procedure Act.
  The IRS relies principally on Zale Corp. v. IRS, 481 F.Supp. 486
 (D.D.C.1979), which has been followed by the Sixth and Seventh Circuits, see
 White v. IRS, 707 F.2d 897, 900 (6th Cir.1983);  King v. IRS, 688 F.2d
 488, 495-96 (7th Cir.1982).  We cannot agree with those decisions.  FOIA is a
 structural statute, designed to apply across-the-board to many substantive
 programs;  it explicityly accommodates other laws by excluding from its
 disclosure requirement documents "specifically exempted from disclosure" by
 other statutes, 5 U.S.C. s 552(b)(3);  and it is subject to the provision,
 governing all of the Administrative Procedure Act of which it is a part, that
 a "[s]ubsequent statute may not be held to supersede or modify this
 subchapter ... except to the extent that it does so expressly," 5 U.S.C. s
 559. [FN2]  We find it impossible to conclude that such a statute was sub
 silentio repealed by s 6103.  Insofar as is relevant to the issue here, the
 latter enactment does no more than what is done by all nondisclosure statutes
 covered by Exemption 3:  it prohibits the disclosure of certain information
 (returns and return information).  It differs from most other nondisclosure
 statutes only in that it specifies lengthy exceptions to its rule of
 nondisclosure.  Not generally, but only in the painstaking detail of these
 exceptions, can it be considered--what Zale called it, 481 F.Supp. at
 489--a "comprehensive scheme."  But that sort of comprehensiveness has nothing
 to do with the appropriateness of continuing application of FOIA.  Even the
 simplest nondisclosure statute, which makes no exceptions, is "comprehensive"
 in that sense--brief but comprehensive instead of lengthy and comprehensive.
 It would be another matter if s 6103 established some rules and procedures--
 duplicating those of FOIA--for individual members of the public to obtain
 access to IRS documents.  But it does not.  The entirety of its "comprehensive"
 detail relates to exceptions from the prohibition of disclosure--and even all
 of these, with three minor exceptions, see s 6103(k)(1), (3);
 s 6103(m)(1), pertain to disclosure to specified private individuals (e.g.,
 the taxpayer to whom the information relates) or government officials, rather
 than to the public at large.  That is to be contrasted with s 6110, enacted at
 the same time as s 6103, which specifically requires that IRS written
 determinations be "open to public inspection," and establishes procedures to
 obtain and restrain disclosure, time limits, the level of assessable fees, and
 an action to compel or restrain disclosure in the Claims Court.  That scheme is
 a "comprehensive" one in the relevant sense--that is, in the sense of
 duplicating and hence presumably replacing the dispositions of FOIA.
 (Significantly, Congress did not leave us to speculate whether it was
 comprehensive enough to constitute an implicit pro tanto repeal of FOIA;  the
 last subsection specifies that the prescribed civil remedy in the Claims Court
 shall be the exclusive means of obtaining disclosure, s 6110(l).)

      FN2. We do not suggest that an earlier Congress can limit the manner in
     which a later Congress may express its legislative acts.  This provision,
     like any other, can presumably be repealed by implication.  But it
     assuredly increases the burden that must be sustained before an intent to
     depart from the Administrative Procedure Act can be found.

  From what has been said, it should be clear that we do not share Zale's
 concern over our "duty to reconcile" FOIA and s 6103, 481 F.Supp. at 488,
 or over preventing FOIA from "negat[ing], supersed[ing], or otherwise frustrat
 [ing] the clear purpose and structure of s 6103," id. at 489.  The two
 statutes seem to us entirely harmonious;  indeed, they seem to us quite
 literally made for each other:  Section 6103 prohibits the disclosure of
 certain IRS information (with exceptions for many recipients);  and FOIA,
 which requires all agencies, including the IRS, to provide nonexempt
 information to the public, establishes the procedures the IRS must follow in
 asserting the s 6103 (or any other) exemption.  Of *150 **82 course
 FOIA can loosely be said to "frustrate" the purposes of s 6103 in that it
 places upon the IRS the burden of sustaining its claimed exemption in de novo
 judicial review.  But if that sort of frustration requires the conclusion that
 s 6103 must have been intended to supersede FOIA, then all subsequently
 enacted nondisclosure statutes supersede FOIA, and Exemption 3 has no
 application except to statutes already on the books when FOIA was passed--a
 state of affairs no one has suggested.  For these reasons, and for some further
 reasons discussed in Judge Sirica's opinion in Britt v. IRS, 547 F.Supp.
 808, 809-13 (D.D.C.1982), a decision of our district court subsequent to
 Zale and reaching the opposite conclusion, we hold, in agreement with the
 Fifth and Eleventh Circuits, that Section 6103 does not supersede FOIA but
 rather gives rise to an exemption under Exemption 3, 5 U.S.C. s 552(b)(3).
 See Linsteadt v. IRS, 729 F.2d 998, 1001-03 (5th Cir.1984);  Currie v.
 IRS, 704 F.2d 523, 526-28 (11th Cir.1983).
                                       III
  [2] The Church objects to the IRS's decision not to search the files of
 its regional and district offices other than those in Los Angeles and
 Covington, Kentucky.  FOIA requires agencies to make records available in
 response to any request "made in accordance with published rules stating the
 time, place, fees (if any), and procedures to be followed."  5 U.S.C. s
 552(a)(3)(B).  The IRS does not have a central file of records in which copies
 of all documents in its possession are retained.  Its regulations therefore
 require requests to be made to the office of the official who is responsible
 for the control of the records requested, or if the person making the request
 does not know the official responsible, to the office of the director of the
 IRS district office in the district where the requester resides.  26
 C.F.R. s 601.702(c)(3)(iii) (1984).  The regulations specify in some detail
 which officials are responsible for documents and give their addresses.  26
 C.F.R. s 601.702(g).
  It is undisputed that the Church did not direct its request to the officials
 in charge of the documents in regional and district offices, nor to the office
 of the director of the IRS district office in the district where the Church
 resides, but rather to the National Office of the IRS.  The Service caused a
 search to be made of the records in its National Office, and in addition
 (though it was not technically required) of the records in the two field
 offices particularly pertinent to the Church's operations.  In view of the
 statutory command that requests be made in accordance with published rules, the
 clarity of those rules, and the reasonableness of the IRS's treatment of the
 misdirected request, we find no merit in the Church's contention that the IRS's
 failure to inform it earlier that the request for a search of all district and
 regional offices was misdirected should have led the District Court to require
 a search of those offices.
                                       IV
  The Church also challenges the IRS's decision to limit the search to files
 whose titles refer to the California Church.  That decision involved two
 separate but related limitations:  (1) restricting the search to those files
 whose subjects indicate that their contents are related to Scientology, the
 Hubbards, etc., rather than searching through all files, whatever their
 subject, that might contain some information responsive to the request;  and
 (2) restricting the search further to those files whose subject is the
 California Church on grounds that the information in all requested files on
 other Scientology organizations, the Hubbards, etc., is return information and
 therefore exempt from disclosure to the California Church.
  [3][4] The IRS justifies the first restriction on grounds that a request for
 all information on Scientology in its files fails to meet the statutory
 requirement of "reasonably describ[ing] such records," 5 U.S.C. s
 552(a)(3).  It is firmly established that "an agency is not 'required to
 reorganize [its] files in response to [a plaintiff's] request *151 **83 in
 the form in which it was made.' "  Goland v. CIA, 607 F.2d 339, 353
 (D.C.Cir.1978) (quoting Irons v. Schuyler, 465 F.2d 608, 615 (D.C.Cir.),
 cert. denied, 409 U.S. 1076, 93 S.Ct. 682, 34 L.Ed.2d 664 (1972)).  "[I]f an
 agency has not previously segregated the requested class of records production
 may be required only 'where the agency [can] identify that material with
 reasonable effort.' "  Id. (quoting National Cable Television
 Association, Inc. v. FCC, 479 F.2d 183, 192 (1973)).  Thus, the IRS would
 doubtless be within the law in restricting its search to files whose subjects
 indicate a connection with Scientology.  It was not required to search through
 every file in its possession to see if a reference to Scientology appeared
 somewhere in it--for example, because a taxpayer claimed a deduction for a
 contribution to a Scientology organization.  However, the problem at this stage
 of the litigation is that the District Court had only the IRS's generalized
 assertion that it had examined the appropriate subject files.  Indeed, it did
 not have even that, because of the further limitation restricting the search to
 the California Church alone, which we will discuss below.  In these
 circumstances, we cannot conclude that the agency sustained the burden of
 justifying its actions, see 5 U.S.C. s 552(a)(4)(B), even with regard to the
 first limitation.  Summary judgment on this point would require an affidavit
 reciting facts which enable the District Court to satisfy itself that all
 appropriate files have been searched, i.e., that further searches would be
 unreasonably burdensome.  Such an affidavit would presumably identify the
 searched files and describe at least generally the structure of the agency's
 file system which makes further search difficult.  Cf. Goland v. CIA, 607
 F.2d at 352-53 (agency met its burden of proving that it made a full search in
 good faith with relatively detailed, nonconclusory affidavits).
  But the first limitation was in any event superseded by the limitation to
 records of the California Church.  The IRS does not appear to dispute that the
 Church's request reasonably describes information directly relating to some
 other Scientology organizations and contained in files whose titles would
 enable identification without undue burden.  Its decision not to search these
 files appears to rest exclusively on grounds that they contain only return
 information protected by Section 6103.
  [5] The Church asserts that these grounds are patently inadequate, since (1)
 return information consists only of data that identify or can be associated
 with the taxpayer to whom they pertain, (2) FOIA's requirement that "reasonably
 segregable" portions of otherwise exempt documents must be provided, 5
 U.S.C. s 552(b), would mandate production of the data after redaction of
 material that enable identification or association, and (3) the possibility of
 redaction can only be assessed on a document-by-document basis.  The crucial
 first premise of this argument has been considered by this court en banc and,
 by an opinion issued simultaneously with the present opinion, has been
 rejected.  Church of Scientology v. IRS, 792 F.2d 153 (D.C.Cir. 1986)(en
 banc).  The mere deletion of identifying material will not cause the remainder
 of the return information to lose its protected status, and document-by-
 document examination to determine the possibility of redaction for that purpose
 is therefore unnecessary.
  [6] This is still not sufficient, however, to sustain the IRS's bald
 contention that it need not search the file of any Scientology organization
 other than the California Church.  That contention would be justified only if,
 as a matter of law, all information in IRS files is return information.
 That is unquestionably not so.  Congress would not have adopted such a detailed
 definition of return information in Section 6103 if it had simply intended
 the term to cover all information in IRS files;  and we have no authority to
 substitute the one disposition for the other.  Here the Church requested, for
 example, information from Treas/IRS System Number 26.005, "File of Persons
 Making Threats of Force or Forcible Assaults."  If such a files system exists,
 it seems unlikely that its contents consist entirely *152 **84 of return
 information as defined in Section 6103.  In any case, before the IRS's claim
 that all information in the requested files is protected can be upheld, it must
 make an appropriate showing that all information comes within the statutory
 definition.
  [7] For the reasons just given, the District Court erred in accepting the
 IRS's blanket assertion that all information responsive to the Church's request
 in files not relating to the California Church was exempt from disclosure.
 This does not mean, however, that the IRS must, as the Church would have us
 hold, prepare a Vaughn index of all documents in its files relating to third
 parties for which it claims an exemption under Section 6103 and Exemption
 3.   See Vaughn v. Rosen, 484 F.2d at 826-29.  If the IRS claims that a
 particular document is exempt from disclosure because it contains information
 on one of the specific subjects protected by Section 6103--for example,
 information about deductions claimed by a taxpayer--a Vaughn index may be
 required in order to show that the document does not contain segregable
 portions that could be disclosed without revealing such information.  When,
 however, a claimed FOIA exemption consists of a generic exclusion, dependent
 upon the category of records rather than the subject matter which each
 individual record contains, resort to a Vaughn index is futile.  Thus, in
 NLRB v. Robbins Tire & Rubber Co., 437 U.S. 214, 98 S.Ct. 2311, 57 L.Ed.2d
 159 (1978), the Supreme Court upheld, without any provision of a Vaughn
 index, the Labor Board's refusal to provide under FOIA witness statements
 obtained in the investigation of pending unfair labor practice proceedings.  A
 Vaughn index would have served no purpose since, as the Court held,
 Exemption 7(A), which excludes from required disclosure "investigatory
 records ... to the extent that the production of such records would ...
 interfere with enforcement proceedings," 5 U.S.C. s 552(b)(7)(A), did not
 require a showing that each individual document would produce such
 interference, but could rather be applied generically, to classes of records
 such as witness statements.  See also Campbell v. Department of Health and
 Human Services, 682 F.2d 256, 265 (D.C.Cir.1982) (government required to
 provide affidavits but not Vaughn index to establish applicability of
 Exemption 7(A));  Brinton v. Department of State, 636 F.2d 600, 606
 (D.C.Cir.1980) (invocation of the deliberative process exclusion of Exemption 5
 upheld on the basis of affidavits and no index);  Mervin v. FTC, 591 F.2d
 821, 826 (D.C.Cir.1978) (invocation of the attorney's work product exclusion of
 Exemption 5 upheld on the basis of affidavit and no index);  Barney v. IRS,
 618 F.2d 1268, 1272-74 (8th Cir.1980) (invocation of Exemption 7(A) upheld on
 the basis of affidavits and no index).  If, therefore, the Commissioner's
 assertion of a Section 6103 exemption rests upon such generic grounds, he
 will ordinarily be able to make the requisite showing with an affidavit
 sufficiently detailed to establish that the document or group of documents in
 question actually falls into the exempted category.  Some portions of s 6103
 are plainly susceptible of such generic application--particularly that portion
 which defines protected return information to include all information, no
 matter what its subject, "received by, recorded by, prepared by, furnished to,
 or collected by the Secretary with respect to a return or with respect to the
 determination of the existence, or possible existence, of liability (or the
 amount thereof) of any person ... for any tax, penalty, interest, fine,
 forfeiture, or other imposition, or offense," 26 U.S.C. s 6103(b)(2)(A).
  In light of the foregoing discussion, the IRS must either conduct a new search
 for information responsive to the Church's request that refers to third parties
 or establish through affidavits that all information about third parties in
 identifiable files requested by the Church is generically protected by
 Section 6103.  If a new search produces any third party information
 responsive to the Church's request, the IRS must either disclose it or justify
 withholding it in light of one of the FOIA exemptions *153 **85 through
 affidavits and, where necessary, Vaughn indices.
  [8] The IRS's search uncovered a large number of documents responsive to the
 Church's request and relating specifically to the California Church.  It
 claimed exemption for the majority of these documents--concretely the Tax Court
 case documents--on the ground that disclosure "would seriously impair Federal
 tax administration," 26 U.S.C. s 6103(c).  Selected portions of a much
 smaller group of documents not related to the Tax Court case were withheld
 under various FOIA exemptions because they contained personal information or
 third party return information, or because they exceeded the scope of the
 Church's request.  The Court upheld the IRS's claim of exemption on the basis
 of in camera examination of a representative sample of the documents, without
 the benefit of detailed public affidavits or indices. [FN4]  While in camera,
 individual inspection of each of a small number of documents without detailed
 public affidavits and Vaughn indices is sometimes acceptable, see Currie
 v. IRS, 704 F.2d at 530-31, such an approach cannot be applied to large numbers
 of documents--much less to large numbers of documents that represent only a
 sampling.  It places unrealistic and unsustainable demands upon the trial court
 and the reviewing appellate panel, and therefore must be replaced or
 supplemented by the adversary testing which public affidavits and indices seek
 to provide.  See Vaughn v. Rosen, 484 F.2d at 825.  With respect to these
 documents, therefore, the District Court should have required the IRS to
 sustain its burden of proving that the documents it sought to withhold were
 exempt from disclosure through an appropriate combination of detailed public
 affidavits and (if necessary) indices, resorting to in camera examination of
 documents and affidavits only where these proved inadequate.  We note in this
 regard that the asserted exemption for documents whose disclosure "would
 seriously impair Federal tax administration," 26 U.S.C. s 6103(c), is
 analogous to the exception at issue in Robbins, supra, for documents whose
 disclosure would "interfere with enforcement proceedings," 5 U.S.C. s
 552(b)(7)(A), and like that exemption should be sustainable generically, as
 applied to certain categories of documents, on the basis of affidavits and
 without Vaughn indices.

      FN4. The District Court does mention that the IRS indexed twenty-one
     documents located in its National Office, but its opinion seems to suggest
     that the court relied entirely upon in camera examination.  See Church
     of Scientology of California v. IRS, supra, at ---- - ----.

  The order of the District Court is vacated and this case is remanded to the
 District Court for further proceedings consistent with this opinion.  At the
 conclusion of such proceedings, the Church may renew its motion for an award of
 attorney fees if it so desires.
  So ordered.