STEPHEN F. WILLIAMS, Circuit Judge:
In the four decisions under review, Department of the Treasury, Financial Management Service, 25 FLRA 560 (1987); Department of Health and Human Services, Social Security Administration, Baltimore, Md. and Social Security Administration, Great Lakes Program Service Center, Chicago, Illinois, 25 FLRA 828 (1987); Department of the Navy, Portsmouth Naval Shipyard, Portsmouth, New Hampshire, 24 FLRA 209 (1986); National Labor Relations Board, Office of the General Counsel and the Board, 24 FLRA 917 (1986), the Federal Labor Relations Authority ordered government agencies to comply with union requests for the names and home addresses of agency employees working in the relevant bargaining units. The unions stated that they needed the information to perform their representational duties effectively and that they were therefore entitled to it by 5 U.S.C. § 7114(b)(4) (1982). This requires agencies
to furnish to the exclusive representative involved, or its authorized representative, upon request and, to the extent not prohibited by law, data . (B) which is reasonably available and necessary for full and proper discussion, understanding, and negotiation of subjects within the scope of collective bargaining.
Relying on its decision in Farmers Home Administration Finance Office, St. Louis, Missouri, 23 FLRA 788 (1986), affd in substantial part and remanded sub nom. Department of Agriculture v. FLRA, 836 F.2d 1139 (8th Cir.1988), vacated and remanded, — U.S. —, 109 S.Ct. 831, 102 L.Ed.2d 964 (1989), the Authority held that' agencies commit unfair labor practices when they refuse to supply authorized unions with employees' names and home addresses.
Each of the agencies appealed to this court, where the cases were consolidated. They argue first that the information is not "necessary for . discussion, understanding, and negotiation of subjects within the scope of collective bargaining," and second that disclosure is "prohibited by law," specifically by the Privacy Act, 5 U.S.C. § 552a. We agree with all the other circuits that have addressed the first issue that, under the deference the Authority is due on such matters, its interpretation of § 7114(b)(4) is permissible. Nevertheless, we must set aside the Authority's decisions; we are persuaded that release of the information is prohibited by the Privacy Act. Reviewing this issue de novo, we find that the Authority erred when it determined that disclosure fell within either the Act's exception for disclosures required by the Freedom of Information Act, 5 U.S.C. § 552(b)(2), or the exception for disclosures made in accordance with a "routine use," 5 U.S.C. § 552a(b)(3). Thus we grant the agencies' petitions for review and deny the FLRA's applications for enforcement.
I. Disclosure "Necessary" for the Collective Bargaining Process
To the extent that the FLRA is interpreting its own enabling statute, we cannot upset its "reasonable and defensible construction[ ]." Bureau of Alcohol, Tobacco and Firearms v. FLRA, 464 U.S. 89, 97, 104 S.Ct. 439, 444, 78 L.Ed.2d 195 (1983) (FLRA intended by Congress to use "specialized expertise" to "give content to the principles and goals set forth in the Act"). Given this standard of review, it is not surprising that every circuit court that has reviewed the matter has upheld the FLRA's view of whether disclosure is "necessary" for the collective bargaining process under § 7114(b)(4). Department of the Navy v. FLRA, 840 F.2d 1131, 1137-39 (3d Cir.1988); Department of the Air Force v. FLRA, 838 F.2d 229, 231-32 (7th Cir.1988); Department of Agriculture v. FLRA, 836 F.2d 1139, 1142 (8th Cir.1988), vacated and remanded, — U.S. —, 109 S.Ct. 831, 102 L.Ed.2d 964 (1989); Department of Health and Human Services v. FLRA, 833 F.2d 1129, 1131-34 (4th Cir. 1987); AFGE v. FLRA, 786 F.2d 554, 557 (2d Cir.1986). We agree.
The agencies first contend that § 7114(b)(4)(B) requires disclosure only of data relating directly to subjects of contract negotiation; it regards the employees' names and addresses as relating merely to "the union's relationship with bargaining unit employees." Brief for Government Agencies 21. The FLRA, on the other hand, views as sufficient a relationship to the "union's ongoing representational responsibilities." NLRB, 24 FLRA at 920. It found in Farmers Home Administration that disclosure would "enable the Union[s] to communicate effectively and efficiently, through direct mailings to individual employees." 23 FLRA at 796.
This analysis is not unreasonable. As the Fourth Circuit noted, "The Union's duties as the exclusive representative of agency employees do not begin and end abruptly with each round of negotiations but continue during the interim." Department of Health and Human Services, 833 F.2d at 1132. The statutory references to "discussion" and "understanding" of subjects within the scope of collective bargaining provide some support for the Authority's reading. If the information is used to discover employee concerns, clearly it can enhance the usefulness of collective bargaining.
In addition, the Authority's view corresponds to that of private sector labor relations law. In Prudential Insurance Co. v. NLRB, 412 F.2d 77, 83-85 (2d Cir.1969), the court found that union communications with members of the bargaining unit related to the union's representational obligations. But compare id. at 85-87 (Friendly, J., dissenting) (arguing that true union purpose was recruitment of new members, a goal he found inadequate to justify forced release of employee names and addresses). As we agree that the FLRA's expansive interpretation is reasonable, we will not disturb it.
Next the agencies argue that the names and addresses are not "necessary" for the purpose stated because alternate means are available for communication between unions and government employees— desk drops, bulletin boards, "direct distributions," meetings and direct personal contact. Brief for Government Agencies 23. In Farmers Home Administration, the FLRA noted two advantages of mailings to home addresses. First, "content, timing and frequency" of communications would be entirely within union discretion, thus excluding the possibility of agency interference. 23 FLRA at 796-97. Second, the communications would be received under circumstances where employees could give them extended attention "without regard to the time constraints inherent in their work environments [or] any restraint the employee may feel as a result of the presence of agency management." Id. at 797.
While there is no evidence in the record either that agency management has interfered with on-the-job communications, or that employees could not pocket materials received at work for leisurely study at home, we do not believe the Authority's finding that release is "necessary" is either arbitrary or capricious. Necessity is a mat ter of degree, and in many contexts courts have found a statutory requirement of necessity satisfied even when alternative means were feasible. See NRDC v. Thomas, 838 F.2d 1224, 1236-38 (D.C.Cir.1988) (citing cases); cf. Board of Trustees of State University of New York v. Fox, — U.S. -, -, 109 S.Ct. 3028, 3031-33, 106 L.Ed.2d 388 (1989) (speech restriction may be no broader than "necessary" to achieve goal even though it is not least restrictive alternative). Where, as here, the Authority clearly regarded the burden of disclosure on the agency and on employees as quite modest, and was entitled to do so for purposes of the interpretation of the Federal Labor Management Relations Act (FOIA and Privacy Act matters are a different story, discussed below), modest advantages realized through at home mailings are enough to sustain its judgment. Again, the Authority's view agrees with that of private sector labor law. Prudential Insurance Co. v. NLRB, 412 F.2d at 81 — 83; but see id. at 85-86 (Friendly, J., dissenting) (alternative means of communication were adequate though not ideal).
Because it believed that home mailings would facilitate union-employee communications in certain ways, the Authority adopted a presumption of necessity, which could be rebutted "where, for example, the evidence discloses that a union has acted in a manner which leads to the conclusion that the employees whose addresses would be disclosed would be in imminent danger if the union knew where they lived." Farmers Home Administration, 23 FLRA at 798. We assume that the Authority will be alert to any special' instances where disclosure imposes such safety risks or other out-of-the-ordinary burdens. The Eighth Circuit on its own motion conditioned its affirmance of the Authority's disclosure order on the withholding of names and addresses of employees who so requested, observing that mailings by a union to those who did not wish to receive them would scarcely serve the public interest. Department of Agriculture, 836 F.2d at 1143-44. In response to the FLRA's petition for certiorari, however, the Solicitor General rejected this position, saying that he found no basis for an " 'individualized' veto" in the statute. See Brief for the Respondents 17-18, FLRA v. Department of Agriculture, — U.S. —, 109 S.Ct. 831, 102 L.Ed.2d 964 (1989). (The Supreme Court remanded the case for reconsideration in light of "routine use" notices filed by the relevant agencies.) But compare Department of the Air Force v. FLRA, 838 F.2d 229, 233 (7th Cir.1988) (suggesting desirability of individual check-off system, but not mandating it in light of absence of request). While we uphold the FLRA's rejection of a case-by-case approach as within its authority, we rest our conclusion on the assumption that it will be sensitive to legitimate claims that disclosure will impose undue burdens.
II. The Privacy Act
The statute on which the FLRA relies for its disclosure orders, 5 U.S.C. § 7114(b)(4), requires agencies to supply data only "to the extent not prohibited by law." The agencies contend that release of employee names and addresses would violate the Privacy Act, which prohibits the disclosure of personal information about federal employees without their consent. 5 U.S.C. § 552a(b) (1982). The FLRA does not dispute that the information is protected by the general language of the Privacy Act, but argues that the release falls within two explicit exceptions. First, § 552a(b)(2) allows disclosure that is "required under section 552 of this title [the Freedom of Information Act]." Second, § 552a(b)(3) allows disclosure "for a routine use." Under the latter provision, disclosure is proper only if it is in accordance with a routine use notice, published in the Federal Register by the relevant agency and describing "the categories of users and the purpose of such use." See 5 U.S.C. § 552a(e)(4)(D).
As the FLRA is not charged with a special duty to interpret either the Privacy Act or the FOIA, we do not defer to its interpretations of those statutes but review them de novo. Illinois National Guard v. FLRA, 854 F.2d 1396, 1400 (D.C.Cir.1988); Department of the Treasury v. FLRA, 837 F.2d 1163, 1167 (D.C.Cir.1988); Professional Airways Systems Specialists v. FLRA, 809 F.2d 855, 857 n. 6 (D.C.Cir.1987). We do not believe that the FLRA's reliance on the FOIA exception to the Privacy Act can survive the recent Supreme Court decision in Department of Justice v. Reporters Committee for Freedom of the Press, — U.S. —, 109 S.Ct. 1468, 103 L.Ed.2d 774 (1989). Nor are we persuaded that disclosure of employees' names and home addresses to union representatives is authorized by the only routine use notice relevant here, one published by the Office of Personnel Management. OPM has interpreted the routine use to require a rigorous showing of the need for direct mailings in light of the available alternate methods of communication, and we owe great deference to its interpretation of its own regulations.
A. The Freedom of Information Act Exception
While the Privacy Act generally prohibits disclosure of personnel information, it excepts disclosures "required under" FOIA. 5 U.S.C. § 552a(b)(2). FOIA in turn generally requires disclosure, but exempts information in "personnel and medical files and similar files the disclosure of which would constitute a clearly unwarranted invasion of personal privacy." 5 U.S.C. § 552(b)(6). Application of exemption 6 requires a balancing of the harm to the individual whose privacy is breached against the public interest served by disclosure. See Department of the Air Force v. Rose, 425 U.S. 352, 372, 96 S.Ct. 1592, 1604, 48 L.Ed.2d 11 (1976).
The FLRA rejected the agencies' invocation of exemption 6, stating that "[o]n balance, . the public interest to be furthered by providing the Union with an efficient method to communicate with unit employees it must represent far outweighs the privacy interests of individual employees in their names and home addresses." Farmers Home Administration, 23 FLRA at 793. With one exception, the circuit court decisions upholding disclosure have similarly considered the special public interest in advancing collective bargaining as an aspect of the disclosure value, and, indeed, as the clinching value. See Department of Navy, 840 F.2d at 1135-37; Department of Agriculture, 836 F.2d at 1142-44; Department of Health and Human Services, 833 F.2d at 1134-36; AFGE, 786 F.2d at 556-57.
In Reporters Committee, however, the Court made clear that under FOIA the disclosure interest must be measured in terms of its relation to FOIA's central purpose — "to ensure that the Government's activities be opened to the sharp eye of public scrutiny." 109 S.Ct. at 1482 (emphasis in original); see also id., 109 S.Ct. at 1481 ("democracy cannot function unless the people are permitted to know what their government is up to ") (quoting EPA v. Mink, 410 U.S. 73, 80, 93 S.Ct. 827, 832, 35 L.Ed.2d 119 (1973) (emphasis in original)). However great might be the generalized public interest in FBI "rap" sheets (criminal records) of non-government officials, the Court found it irrelevant to the interest in government activities and thus to FOIA privacy balancing. Although the context in Reporters Committee was the special privacy exemption for law enforcement records, exemption 7(C), we see no reason why the character of the disclosure interest should be different under exemption 6. While exemption 6 precludes only "a clearly unwarranted invasion of personal privacy" (emphasis added), that differ ence between it and exemption 7(C) goes only to the weight of the privacy interest needed to outweigh disclosure.
A recent Supreme Court decision might be thought to undermine our view of the restricted character of the disclosure interest for purposes of exemption 6. United States Department of Justice v. Tax Analysts, — U.S. -, 109 S.Ct. 2841, 106 L.Ed.2d 112 (1989), finds that Justice Department copies of district court tax decisions are encompassed by FOIA, although admittedly their release "adds nothing whatsoever to public knowledge of government [executive branch] operations," see id., 109 S.Ct. at 2854 (Blackmun, J., dissenting). In Tax Analysts, however, the Court was not considering any FOIA exemption at all, but was defining statutory phrases such as "agency records." It chose to do so in rather neutral terms, independent of FOIA's overarching purpose. But the Court's privacy "weighing" under exemption 7(C) clearly presents a closer analogy for defining exemption 6 weighing than did the issue at stake in Tax Analysts.
Since Reporters Committee, we have balanced the disclosure interest in a list of the names and home addresses of retired or disabled federal employees against their privacy interests under exemption 6, and have found the latter predominant. National Association of Retired Federal Employees v. Homer ("NARFE"), 879 F.2d 873 (D.C.Cir.1989). Indeed, NARFE found the interest in disclosure to be absolute zero. Id. at 879. Again we find the balance tilts in favor of privacy.
In analysing the privacy interest in NARFE, we considered the nature and scope of the privacy invasions that would flow from disclosure, as inferred from "the characteristic(s) revealed by virtue of being on the particular list." Id. at 877. We noted that the list requested would by its nature also disclose that the persons listed were retired or disabled and receiving a monthly annuity check from the federal government. "Any business or fund-raising organization for which such individuals might be an attractive market could, get from the Government, at nominal cost, a list of prime sales prospects to solicit." Id. at 876. Cheap access to such lists would expose the annuitants " 'to an unwanted barrage of mailings and personal solicitations,' " id. at 876, quoting Minnis v. Department of Agriculture, 737 F.2d 784, 787 (9th Cir.1984). While the financial security of federal annuitants may somewhat exceed that of current federal workers, we doubt that the difference is enough to justify more than a very modest discount of the individuals' privacy interest, which in NARFE we characterized as "significant." Id. at 879. We note that entrepreneurs have filed FOIA requests for specific names of classes of current government employees in order to aid them in business solicitation. See Schwaner v. Department of the Air Force, 698 F.Supp. 4 (D.D.C.1988), appeal pending, No. 88-5341 (D.C.Cir.) (request for names and duty stations of certain ranks of Bolling Air Force personnel for purposes of life insurance solicitation).
On the disclosure side of the balance, again we find NARFE only modestly distinguishable. To be sure, the names of current workers might provide leads for an investigative reporter seeking to ferret out what "government is up to." But the same may be said as to the retirees involved in NARFE; indeed, recent retirees might sometimes, because of their relative invulnerability to retaliation, be an especially rich source of revelations. Moreover, the zealous investigator has an alternative means of access to current workers that is unavailable as to retirees — face-to-fáce conversation attained simply by following other leads and roaming government hallways. Concededly, access through home address lists might on occasion offer the investigator an advantage: a potential witness reached at home might assess the risk of discovery by superiors as less than if reached at work, and accordingly be more candid. While this advantage raises the public interest in disclosure above the "nothing" at which NARFE valued the disclosure interest in retirees' names and addresses, we do not find it enough to outweigh the workers' significant interest in privacy.
The remaining question is whether this balance should be adjusted in light of the FLRA's legitimate finding that the Federal Labor Management Relations Act establishes another public interest in disclosure, namely in disclosure to labor unions for collective bargaining purposes. The Act specifically identifies a public interest in public sector collective bargaining, see 5 U.S.C. § 7101(a); NTEUv. FLRA, 810 F.2d 295, 300 (D.C.Cir.1987) (Congress believed that collective bargaining in the federal sphere would contribute to effective running of public business), and the FLRA's determinations here rest on a provision of that Act that expressly calls for disclosure as a means to facilitate that interest, see 5 U.S.C. § 7114(b)(4). Other circuit courts have invoked these disclosure values in the Privacy Act-FOIA balancing, but they did so without explanation. Reporters Committee requires that this reliance on nonFOIA disclosure interests be either explained or abandoned.
Reporters Committee itself stated that "the identity of the requesting party has no bearing on the merits of his or her FOIA request," with the exception of the case where a privacy interest is based on a claim of privilege and the person protected by the privilege seeks the information for himself (giving as an example a FOIA request by the subject of a presentence report). 109 S.Ct. at 1480. But the statement does not necessarily mean that there is no exception to the general rule that the public interest in disclosure under FOIA should be defined exclusively in terms of finding out what the "government is up to." Nothing in the passage suggests that the Court had considered and rejected the relevance of public interest objectives identified by Congress in other disclosure statutes. Moreover, the argument here is not that the identity of the requester should alter the disclosure interest, but rather that a congressional (non-FOIA) disclosure mandate might do so.
On the other hand, the language of the Privacy Act itself is hard to square with such a broad view. Under 5 U.S.C. § 552a(b)(2), disclosure of a personal record, without the consent of the person to whom it pertains, is prohibited "unless disclosure of the record would be . required under section 552 of this title [FOIA]." The reading proposed by the Authority would in effect construe this as encompassing disclosures required "under FOIA or any agency decision based on a disclosure-related statute." Alternatively, with more nuance but considerably more complication, it might apply to disclosures "required where the disclosure value under FOIA, and under any congressionally authorized agency disclosure decision, in the aggregate outweigh the privacy interest." One can, indeed, imagine numerous variations in which to cast this gloss.
Privacy Act exception b(2) speaks only of FOIA. We do not believe we are entitled to engage in the sort of imaginative reconstruction that would be necessary to introduce collective bargaining values into the balancing process. Consistent with the holding in NARFE, we find that federal employees' have privacy interests in their names and home addresses that must be protected and that the relevant public interest in disclosure, though not nothing, is outweighed.
Thus we turn to the routine use exception of the Privacy Act, an independent ground potentially supporting the FLRA's holding that release of the employees' names and addresses is not prohibited by law.
B. The Routine Use Exception
The "routine use" exception to the Privacy Act, 5 U.S.C. § 552a(b)(3), allows disclosure of personnel records
for a routine use as [1] defined in subsection (a)(7) of this section [5 U.S.C. § 552a(a)(7)] and [2] described under subsection (e)(4)(D) of this section [5 U.S.C. § 552a(e)(4)(D) ].
The effect of the first constraint is to confine routine use disclosures to ones that are "compatible with the purpose for which [the information] was collected," 5 U.S.C. § 552a(a)(7); the agencies raise no issue on that score. Instead, they question whether the proposed disclosure complies with the requirement that the disclosure fall within the uses "described under" 5 U.S.C. § 552a(e)(4)(D). This provision requires an agency maintaining personnel records to describe in a Federal Register notice "each routine use of the records ., including the categories of users and the purpose of such use." The agencies argue that OPM's routine use notice, the only one relied on by the Authority and unions, does not encompass disclosure for the present purposes.
The Office of Personnel Management maintains "Official Personnel Files" that contain federal employees' names and home addresses. These remain its responsibility even though they are located physically in the government agencies. Farmers Home Administration, 23 FLRA at 794. OPM's notice of the routine uses for information from an employee's Official Personnel File provides that the records may be used:
j. To disclose information to officials of labor organizations recognized under 5 U.S.C. Chapter 71 when relevant and necessary to their duties of exclusive representation concerning personnel policies, practices, and matters affecting working conditions..
Privacy Act of 1974: Publication of Notices of Systems of Records and Proposed New Routine Use, 49 Fed.Reg. 36,949, 36,-956 (Sept. 20, 1984). The FLRA found that the data sought here was covered by OPM's paragraph j. Farmers Home Administration, 23 FLRA at 794.
An agency's interpretation of its own regulations is normally controlling unless it is "plainly erroneous or inconsistent" with the language of the regulation. United States v. Larionoff 431 U.S. 864, 872, 97 S.Ct. 2150, 2155, 53 L.Ed.2d 48 (1977); see also San Luis Obispo Mothers for Peace v. NRC, 789 F.2d 26, 30 (D.C.Cir. 1986) (agency interpretation of its own regulations given "controlling weight" by the courts). Broad deference makes especially good sense for these interpretations; as the agency has the authority to amend the regulation itself, a court's refusal to defer may simply postpone application of the agency's legitimate view. For purposes of determining the scope of OPM's routine use notice, then, an official OPM interpretation would be entitled to great deference.
Unfortunately, the record here is slightly obscure as to OPM's interpretation. The predecessor agency to OPM, the Civil Service Commission, issued guidelines to aid agencies in determining whether releases to labor unions were appropriate. Disclosing Information Covered Under the Freedom of Information Act and the Privacy Act to Labor Organizations Recognized Under Executive Orders 11636 and 11491, As Amended, Federal Personnel Manual, Supplement 711-1, Appendix C (Aug. 10, 1978). The guidelines did not indicate how the existence and adequacy of alternate means of communication should affect the necessity inquiry. In May 1986, the portion of the Manual containing those guidelines was deleted; the subsequent notice of the change indicated that Appendix D of the new chapter was reserved for "material concerning the disclosure of information to labor organizations." Federal Personnel Manual, Table of Changes, Basic Installment 334 (June 24, 1986). Although three years have elapsed since the deletion, OPM has not yet promulgated guidelines concerning disclosure of personnel data to unions. See Federal Personnel Manual, Supplement 711-1 (reserving Appendix D for future guidelines).
Nonetheless, on June 25, 1987 Constance Horner, then the Director of OPM, stated in a letter to Richard Willard, then Assistant Attorney General, that the "current official interpretation of the routine use is set forth in OPM's Home Addresses Cases amicus brief to the FLRA dated July 14, 1986 [Brief for Government Agencies, Addendum D], and will remain in effect pending formal revision and issuance of a new guideline." See Brief for Government Agencies, Addendum B. The cited amicus brief first provides OPM's interpretation of 5 U.S.C. § 7114(b)(4); it contends that disclosure cannot be "necessary" within the meaning of § 7114(b)(4) if "adequate alternative means exist for contacting [the employees]." Amicus Brief at 9. The brief goes on to provide OPM's views as to the meaning of paragraph j of its routine use notice, adopting its previous analysis of § 7114(b)(4). Moreover, because paragraph j has a dual standard of necessity and relevance, the OPM believes that it is more restrictive than § 7114(b)(4). Id. at 20.
Before we decide whether amicus brief's interpretation is a reasonable one, we must decide whether we can properly treat it as OPM's official interpretation. Courts have sometimes declined to defer at all to agency counsel's litigative positions. See, e.g., Ames v. Merrill Lynch, Pierce, Fenner & Smith, Inc., 567 F.2d 1174, 1177 n. 3 (2d Cir.1977) (holding that "an amicus curiae is no more a witness than any other advocate" and refusing to accept agency counsel's "current litigating position" as authoritative). This court has more cautiously noted that "[t]here is some question . whether an interpretive theory put forth only by agency counsel in litigation, which explains agency action that could be explained on different theories, constitutes an 'agency position' for purposes of Chevron [v. NRDC, 467 U.S. 837, 104 S.Ct. 2778, 81 L.Ed.2d 694 (1984) ]." Church of Scientology of California v. IRS, 792 F.2d 153, 162 n. 4 (D.C.Cir.1986) (en banc), aff'd, 484 U.S. 9, 108 S.Ct. 271, 98 L.Ed.2d 228 (1987).
But we think that the reasons for courts' scanting such interpretations are altogether absent here. We can identify two basic concerns for reluctance to defer to agency counsel's litigating position. First, the position may not reflect the views of the agency head(s). Judicial reliance on such a position might (in the statutory interpretation context) lock an agency into a view it never espoused. See Women Involved in Farm Economics v. Department of Agriculture ("WIFE"), 876 F.2d 994, 998-99 (D.C.Cir.1989). That risk may have been especially acute before Chevron made crystal clear that an agency interpreting a statute under an express or implied delegation of authority is free to modify its view. Quite apart from the potential lock-in, an agency informed that its stated reason was inadequate might well reverse field; judicial affirmance on a basis never articulated by the agency could thus produce an unintended result and usurp the agency's function. See SEC v. Chenery Corp., 318 U.S. 80, 88, 63 S.Ct. 454, 459, 87 L.Ed. 626 (1943). In any event, no such concern exists here. Ms. Horner, the agency head, has explicitly adopted the view of the amicus brief. There is no risk that counsel may have acted as "mavericks disembodied from the agency that they represent." Church of Scientology of California v. IRS, 792 F.2d at 165 (Silberman, J., concurring).
Second, a position established only in litigation may have been developed hastily, or under special pressure, or without an adequate opportunity for presentation of conflicting views. Indeed, where statutes specify procedures for a specific type of decision, one engendered solely in litigation will (typically) have skirted those procedures. Cf. WIFE, 876 F.2d at 998-99 (stressing role of statutory obligations to explain actions). Here again we find nothing to justify such a concern. The way in which Director Horner adopted the brief as the official OPM statement seems in no respect to fall short of OPM's usual procedures for interpreting its routine use notice. Guidelines in the Federal Personnel Manual are drafted by OPM staff and approved by the Director, see Federal Personnel Manual, Chapter 711 at § 2-6(1) (June 24, 1986). This seems functionally indistinguishable from the legal staff's preparing the amicus brief and Director Horner's officially adopting it in her letter of June 25, 1987. Thus we have no reason to believe that the interpretive process here was any less thorough, less formal or less open than it would normally be. Nor, of course, did the position represent any kind of agency switch. Compare Judge Silberman's concurring opinion in Church of Scientology, suggesting that acceptance of an agency counsel articulation of a statutory interpretation is appropriate unless it is inconsistent with a prior administration construction, or there is "no link" between the interpretation and administrative practice, or it is "no more than a 'current litigating position.' " 792 F.2d at 165 (citations omitted). Thus we believe it entirely appropriate to treat Mr. Horner's adoption of the amicus brief as an authoritative expression of the agency's views.
We note that this court recently held in WIFE that where an agency developed a regulation under an exemption from 5 U.S.C. § 553's requirement of a statement of the rule's "basis and purpose," counsel's explanation of the rule's underlying theory was acceptable — i.e., did not trigger the Chenery requirement that action unsupported by a valid agency explanation must be remanded for reconsideration. 876 F.2d at 997-1000. Though the case generally supports the view taken here, it is not identical. There the agency position had been taken long before counsel's explanation, so the court's ultimate deference in the case was to a pre-litigation stance. On the other hand, in WIFE, the sole source of any agency explanation of its position was that of counsel in litigation, whereas here counsel and agency head are formally on record expressing the same position and explanation.
Turning to OPM's interpretation of "necessity," we find it quite reasonable. To the extent that alternate means adequately allow the unions to communicate with federal employees, it is reasonable to conclude that it is not "necessary" for the unions to be able to send mail to employees' homes. See Prudential Insurance Co., 412 F.2d at 85-87 (Friendly, J., dissenting) (in view of alternate methods of communication, release of names and home addresses was not a "necessity for union organization and representation"). Although it may seem anomalous that the FLRA and OPM interpret such similar language differently (especially as both § 7114(b)(4) and paragraph j evolved from language developed by the Authority's institutional predecessor, the Federal Labor Relations Council), we cannot require conformity as long as both interpretations are reasonable.
Thus paragraph j of OPM's routine use notice, as explained by the amicus brief, does not authorize the release of employees' names and home addresses to unions without some showing that the alternate means of communication are insufficient. In the absence of any such showing here, we set aside the FLRA's determinations that the routine use exception of the Privacy Act applies.

At oral argument and in supplemental briefing, the union in the case concerning the Social Security Administration argued that the agency was collaterally es-topped from defending itself on the merits before this court because of the Second Circuit's decision in AFGE v. FLRA, 786 F.2d 554 (2d Cir.1986). We find collateral estoppel inappropriate here because there has been "a change or development in the controlling legal principles," namely the Supreme's Court's decision in Reporters Committee, that has rendered the first determination "obsolete or erroneous, at least for future purposes." Commissioner of Internal Revenue v. Sunnen, 333 U.S. 591, 599, 68 S.Ct. 715, 720, 92 L.Ed. 898 (1948); see also Graphic Communications International Union v. Salem-Gravure Division of World Color Press, Inc., 843 F.2d 1490, 1493 (D.C.Cir.1988) ("issue preclusion does not apply when there has been an intervening change in legal principles").
We defer to the FLRA's view that disclosure of employees' name and home addresses are "necessary" for purposes of collective bargaining under § 7114(b)(4) of the Federal Labor Management Relations Act. Nevertheless, we must set aside its decisions because release of that information would violate the Privacy Act. We find that neither the Act's exception for disclosure required by FOIA nor its exception for disclosure pursuant to a routine use notice is applicable in these cases. We deny the Authority's applications for enforcement and grant the government agencies' petitions for review.
So ordered.
. In a ruling on an issue peculiar to the NLRB case, the Authority held that a union proposal to require annual disclosure of the data was negotiable and ordered the agency to bargain over the proposal upon request by the union. This holding was justified solely by the analysis articulated in Farmers Home Administration. See NLRB, 24 FLRA at 920.
. Despite our finding below that the proposed releases do not fall within the "routine uses" exception to the Privacy Act on the facts presented here, that exception may well be available in other cases. Cf. FLRA v. Department of Agriculture, — U.S. —, 109 S.Ct. 831, 102 L.Ed.2d 964 (1989) (remand for reconsideration in light of new "routine use" notices).
. The Court granted certiorari in Reporters Committee on April 18, 1988, 485 U.S. 1005, 108 S.Ct. 1467, 99 L.Ed.2d 697, after oral argument of this case. After the Court's decision issued on March 22, 1989, we ordered supplemental briefing.
. The Seventh Circuit followed our own decision in Reporters Committee and treated the disclosure interest as a fixed quantity for all cases, regardless of the character of the particular information at stake. Department of Air Force, 838 F.2d at 232-33.
. FOIA applies to "agencies," 5 U.S.C. § 552, which are defined to exclude both Congress and the courts of the United States. Id. at § 551(1).