LYNCH, Circuit Judge.
This case comes to us under the union-democracy provisions of the Labor Management Reporting and Disclosure Act of 1959 (“LMRDA”), 29 U.S.C. §§ 401-531 (1994 & Supp. Y 1999).
Thomas Harrington, a member of the United Brotherhood of Carpenters and Joiners of America (“UBC”), alleges that the functions and purposes traditionally accorded to local unions in the New England region of the UBC are now served by the New England Regional Council. That Council, he says, must be treated as a local union and not as an intermediary body. Consequently, Harrington argues, the officers of that Council must be elected in the manner that the LMRDA prescribes for local unions, that is, by direct election by secret ballot among the union members rather than by vote of delegates who are elected from the local unions, as the UBC has chosen to do for the Council. Id. § 481(b),(d) (1994). Harrington filed a complaint with the Secretary of Labor asking her to require the Council to hold a new election as a local union. The Secretary declined for reasons stated in a brief Statement of Reasons.
Harrington sued under the LMRDA. On motion by the Secretary, the district court dismissed his suit. See Harrington v. Herman, 138 F.Supp.2d 232 (D.Mass.2001). Because the Statement of Reasons is insufficient to permit meaningful judicial review, we reverse the district court, vacate the Secretary’s Statement of Reasons and remand the case to the district court with instructions to remand to the Secretary. We do not now decide whether any refusal by the Secretary to bring suit as sought by Harrington would be arbitrary or capricious.
I.
A.
The LMRDA, 29 U.S.C. §§ 401-531, was designed “to ensure that unions would be democratically governed, and responsive to the will of the union membership as expressed in open, periodic elections.” Finnegan v. Leu, 456 U.S. 431, 441, 102 S.Ct. 1867, 72 L.Ed.2d 239 (1982); see also S.Rep. No. 86-187, at 20 (1959) (“It needs no argument to demonstrate the importance of free and democratic union elections.”). The LMRDA balances this purpose with the “countervailing policy recogniz[ing] that unions should be free to conduct their affairs so far as possible and the government should not become excessively involved in union politics.” Reich v. Local 89, Laborers’ Int’l Union, 36 F.3d 1470, 1476 (9th Cir.1994).
[53]*53Title IV of the LMRDA, 29 U.S.C. §§ 481-483 (1994), establishes minimum standards for the election of union officers. The LMRDA provides that “[ejvery local labor organization shall elect its officers not less than once every three years by secret ballot among the members.” Id. § 481(b). However, these direct election requirements do not apply to the selection of officers of “intermediate bodies” of labor organizations.1 Id. § 481(d). Instead, the Act provides:
Officers of intermediate bodies, such as general committees, system boards, joint boards, or joint councils, shall be elected not less often than once every four years by secret ballot among the members in good standing or by labor organization officers representative of such members who have been elected by secret ballot.
Id. § 481(d).2 Thus an intermediate body may choose between direct election or representative election; UBC has chosen the latter.
When a union member wishes to challenge the validity of an election, he must exhaust remedies available under the labor organization’s rules, and he may then file a complaint with the Secretary. Id. § 482(a). Upon receipt of a union member’s complaint, the Secretary investigates the allegations of that complaint. Id. § 482(b). If she determines that there is probable cause to believe that a violation of Title IV occurred and that the violation probably infected the outcome of the election, she must bring suit against the labor organization to set aside the election and to obtain a new election. Id.; Wirtz v. Local 153, Glass Bottle Blowers Ass’n, 389 U.S. 463, 472, 88 S.Ct. 643, 19 L.Ed.2d 705 (1968); see also Heckler v. Chaney, 470 U.S. 821, 834, 105 S.Ct. 1649, 84 L.Ed.2d 714 (1985) (noting that § 482(b) “quite clearly withdrew discretion from the agency and provided guidelines for exercise of its enforcement power”).
B.
In 1996, the UBC, an international union, undertook a dramatic restructuring which established a new three-tier organization of dominant and subordinate UBC bodies. The International remained at the top of the organization. Below the International, the UBC established a group of strong regional entities, called Regional Councils. Lastly, the numerous existing UBC locals were placed at the bottom, subordinate to both the International and the Regional Councils. It appears that before July 1, 1996, the Regional Councils did not exist.
The New England Regional Council (“NERC”) covers UBC members and subordinate UBC locals throughout Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. The [54]*54officers of NERC are not elected directly by local union members, but rather by a secret ballot of delegates who are, in turn, elected by the members of the local unions. The key officer of NERC is the Executive Secretary-Treasurer; he has exclusive authority to submit grievances to binding arbitration, hire or terminate NERC employees, chair the collective bargaining committees, appoint the membership of collective bargaining committees, and appoint the members of the trial committees convened to discipline union members.
Although deprived of many of their previous functions, the UBC locals subordinate to NERC remain independently chartered, have identifiable memberships, elect their own officers, and have their own by-laws. Although the locals do not negotiate collective bargaining agreements, the membership of the locals must vote to ratify the agreements. The locals hold meetings, have their own budgets and bank accounts, and collect members’ dues (a substantial portion of which are then passed on to NERC). Each local is permitted to hire one clerical staff member. Grievances are administered in the early, informal stages by local stewards, but the locals cannot invoke higher levels of the grievance process, including arbitration.
Harrington, a UBC member in Massachusetts, filed a complaint with the Secretary of Labor on September 21, 1999, pursuant to 29 U.S.C. § 482 and 29 C.F.R. § 452.4 (2001), alleging that NERC was essentially a “local” labor organization because it had assumed most of the powers and functions traditionally retained by UBC locals. Harrington contended that because NERC is a “local,” it must elect its officers by direct vote of the local union members, and not by vote of delegates from the local unions, in order to comply with the LMRDA.3
After conducting an investigation, the Secretary concluded in a Statement of Reasons dated April 7, 2000, that NERC is an “intermediate body,” not a “local,” and is therefore permitted to elect its officers either by “secret ballot among the members in good standing or by labor organization officers representative of such members who have been elected by secret ballot.” 29 U.S.C. § 481(d).
In the Statement of Reasons, the Secretary noted that NERC’s bylaws invested it with some of the powers and functions that the union’s locals previously possessed, but that this was insufficient ground upon which to regard NERC as a local rather than as an intermediate body.4 The Secretary stated that there was “no basis in the statute or legislative history for concluding that if intermediate bodies possess certain functions and powers,” they lose the statutory choice of electing officers indirectly and must elect their officers directly. The Secretary concluded that because the investigation found no violation of law in the method by which NERC elected its officers, there was no basis for bringing suit against NERC.
Harrington then filed suit in United States district court challenging the Secretary’s refusal to file an enforcement action. On April 10, 2001, the district court granted the Secretary’s motion to dismiss, reasoning that the Secretary’s decision not to initiate suit was not arbitrary or capricious. Harrington, 138 F.Supp.2d at 235-36. Harrington promptly filed this appeal.
[55]*55II.
Harrington’s principal argument is that the Secretary, in refusing to sue NERC, has retreated without explanation from her prior policies regarding the enforcement of direct election standards. Specifically, Harrington contends that the Secretary’s current position is directly at odds with her established position — as expressed in the regulations and case law — of enforcing the direct election provisions of 29 U.S.C. § 481(b) against so-called intermediate bodies that have, in reality, assumed all of the functions of a local union. Harrington is supported by amicus curiae Association for Union Democracy, Inc, while the UBC and NERC, acting as amici curiae, support the Secretary.5
The Secretary denies any inconsistency and also contends that her action is justified by the LMRDA’s broad purposes, as expressed in its legislative history. Noting that the government “should be careful [not] to undermine self-government within the labor movement,” S.Rep. No. 86-187 at 5, the Secretary argues that she may not decide the appropriate allocation of power between local and intermediate bodies of a labor organization. She contends further that the deference to the union’s allocation of power is consistent with Congress’s recognition of the fact that “in some unions intermediate bodies exercise responsible governing power.” Id. at 20.
Amici the UBC and NERC argue that the Secretary’s decision ultimately may be justified by the evolving nature of labor relations in the construction industry. According to the union, the construction industry has undergone increasing regionali-zation over the past few decades, with construction work becoming concentrated in fewer and larger employers, and employers undertaking a greater number of out-of-state projects.6 The prior UBC organizational structure, which relied on relatively strong locals, was ill equipped to handle the realities of employers operating on a regional scale. Thus, the union contends, the Secretary’s decision to allow strong Regional Councils reflects a sensible 'response to prevailing market conditions. The UBC and NERC urge that a contrary result would not only impinge on internal union affairs,7 but would also handicap their ability to deal with employers. See S.Rep. No. 86-187, at 7 (noting the committee’s belief that the Act should not “weaken unions in their role as collective-bargaining agents”); see also Estr-[56]*56eicher, Deregulating Union Democracy, 2000 Colum. Bus. L.Rev. 501, 503 (2000) (arguing that excessive regulation of internal union affairs will impose unnecessary-compliance costs and weaken the unions’ ability to engage effectively in “economic struggle with employers”).
III.
The Secretary’s decision under Title IV of the LMRDA not to bring an action against a labor organization for violation of 29 U.S.C. § 481 is subject to only narrow judicial review. In Dunlop v. Bachowski, 421 U.S. 560, 95 S.Ct. 1851, 44 L.Ed.2d 377 (1975), the Supreme Court held that the Secretary’s decision is subject to review under the Administrative Procedure Act for whether her decision is “arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law.” Id. at 565, 95 S.Ct. 1851 (quoting 5 U.S.C. § 706(2)(A) and citing 5 U.S.C. §§ 702, 704). The Supreme Court said that “[ejxcept in what must be the rare ease, the court’s review should be confined to examination of the ‘reasons’ statement, and the determination whether the statement, without more, evinces that the Secretary’s decision is so irrational as to constitute the decision arbitrary and capricious.” Id. at 572-73, 95 S.Ct. 1851.
Only the Secretary may bring such a suit for post-election remedies. Local No. 82, Furniture & Piano Moving v. Crowley, 467 U.S. 526, 544, 104 S.Ct. 2557, 81 L.Ed.2d 457 (1984). There are two principal justifications for this exclusivity: “(1) to protect unions from frivolous litigation and unnecessary judicial interference with their elections, and (2) to centralize in a single proceeding such litigation as might be warranted.” Trbovich v. United Mine Workers, 404 U.S. 528, 532, 92 S.Ct. 630, 30 L.Ed.2d 686 (1972). Although Congress mandated that the Secretary bring suit upon a finding that probable cause exists that a violation took place, the Supreme Court has implied that the Secretary may decline to bring suit if the Secretary is not convinced that the “violation ... probably infected the challenged election.” Bachowski, 421 U.S. at 570, 95 S.Ct. 1851 (quotation marks and emphasis omitted); see also Shelley v. Brock, 793 F.2d 1368, 1373 (D.C.Cir.1986).
The Statement of Reasons enables a court to determine whether the Secretary’s refusal to act is contrary to law. Bachowski, 421 U.S. at 568-71, 95 S.Ct. 1851. The courts’ ability to review the Secretary’s decision, however, is not the only justification for requiring the Secretary to provide an adequate statement of reasons. The Supreme Court in Bachow-ski stated that Congress intended that the Secretary provide the complaining union member with a reasoned statement as to why she determined not to proceed. And the Court noted that Congress intended to compel the Secretary in her Statement to “cover the relevant points and eschew irrelevancies,” thereby assuring “careful administrative consideration.” Id. at 572, 95 S.Ct. 1851.
This case raises two significant questions not directly addressed in Bachowski. The first is whether the Secretary has departed from her prior interpretation of the Act, codified at 29 C.F.R. § 452.11 (2001). The second is whether the Secretary, if she is employing the analysis contained in 29 C.F.R. § 452.11, is doing so in a manner consistent with Donovan v. National Transient Division, International Brotherhood of Boilermakers (“Boilermakers ”), 736 F.2d 618 (10th Cir.1984), and Schultz v. Employees’ Federation of the Humble Oil & Refining Co. (“Humble Oil”), No. 69-C-54, 1970 U.S. Dist. LEXIS 12288 (S.D.Tex. Mar. 31, 1970). As to [57]*57the first question, the regulation provides that
The characterization of a particular organizational unit as a “local,” “intermediate,” etc., is determined by its functions and purposes rather than the formal title by which it is known or how it classifies itself.
29 C.F.R. § 452.11. Because the LMRDA does not define the terms “local labor organization” or “intermediate bodies,” the Secretary has room to supply definitions, as she did in the regulation.
The Secretary’s Statement of Reasons, however, does not cite to the language of 29 C.F.R. § 452.11. Indeed, it has language which appears to disavow a functional approach: “There is no basis in the statute or in the legislative history for concluding that if intermediate bodies possess certain functions and powers, they may only elect their officers directly by secret ballot vote among the members of the intermediate body.” This is seemingly inconsistent with the regulation, which requires a “functions and purposes” analysis.
As to the second question, other parts of the Statement then purport to look at the evidence to determine what “functions” are performed by the two entities, perhaps applying the test in the regulations. But the Statement does so without any reference to the Secretary’s own precedents, including the precedents discussed in Boilermakers and Humble Oil.8
In Boilermakers, the Secretary sued to compel the National Transient Division (“NTD”), a unit of the Boilermakers union, to conduct elections in accordance with the provisions of the LMRDA governing “local labor organizations.” See 736 F.2d at 619. The Tenth Circuit held that “[g]iven its structure and functions, we find no reason to reject the Secretary’s characterization of NTD as a local labor organization.” Id. at 623. The court noted first that, because NTD was subordinate to the International and had no subordinate organizational units, it had “the relatively simple organizational structure characteristic of local labor organizations.” Id. But the court reasoned that the “[m]ost important” factor supporting the Secretary’s position was that “NTD performs the functions of a local.” Id. (emphasis added). In so holding, the court relied on the command of 29 C.F.R. § 452.11 to examine the “functions and purposes” of the entity in question. Id. at 622 (quoting 29 C.F.R. § 452.11). The functions of the NTD included the negotiation of collective bargaining agreements, enforcing the agreements, handling grievances, collecting dues from members, maintaining out-of-work lists, and holding meetings at which members express their views. Id.9
[58]*58Similarly to Boilermakers, the Secretary in Humble Oil sued to force an entity purporting to be an intermediate body to conduct elections as a “local” labor organization. 1970 U.S. Dist. LEXIS 12288. The district court, accepting the Secretary’s construction of the Act, found that the supposed intermediate body, the Employees’ Federation, was a statutory local because it performed “the basic local union functions.” Id. at *13 (emphasis added). That is, “[i]t settle[d] grievances; collect[ed] dues and established] wages, benefits, and working conditions by contract negotiations with the employer; and disciplined] its members and officers.” Id. Even though the Employees’ Federation had numerous subordinate local bodies, the court noted that these were mere “administrative arms” with “no separate autonomy” that performed no significant collective bargaining functions. Id. at *11-12.
Given the similarities between this case and Boilermakers and Humble Oil, the Secretary must provide some explanation distinguishing these cases. We cannot now say whether the Secretary has changed her interpretation or departed from the regulation,10 but we can say with fair assurance that substantial questions have been raised and the Secretary’s statement is inadequate to permit us to resolve them. In that sense—the inadequacy of her statement—the statement is arbitrary.
The Secretary denies there has been any change in interpretation or policy, but it is far from evident that this is so, and the Statement of Reasons does not adequately address this topic. The Statement of Reasons does not mention the governing regulation or precedents at all, contains language inconsistent with the “functions and purposes” approach, 29 C.F.R. § 452.11, and, to the extent it purports to apply a functions and purposes approach, fails to address or adequately distinguish the two most pertinent precedents.
The APA provides the applicable standard of review here and it is commonplace in APA review to require an agency to accompany a change in position with an explanation. See P.R. Aqueduct & Sewer Auth. v. EPA, 35 F.3d 600, 607 (1st Cir.1994). Predictability as to how the Secretary will handle these cases is of real value, and if predictability is to be thwarted in favor of other interests, there should be some explanation. An agency’s decision cannot simply depart from the agency’s prior precedent without explaining its reasons for doing so. Atchison, Topeka & Santa Fe Ry. Co. v. Wichita Bd. of Trade, 412 U.S. 800, 808, 93 S.Ct. 2367, 37 L.Ed.2d 350 (1973) (plurality); Shaw’s Supermarkets, Inc. v. NLRB, 884 F.2d 34, 36-37 (1st Cir.1989); JSG Trading Corp. v. USDA, 176 F.3d 536, 544 (D.C.Cir.1999). A deviation from prior interpretations without sufficient explanation may be considered arbitrary and capricious and therefore subject to judicial reversal. See INS v. Yueh-Shaio Yang, 519 U.S. 26, 32, 117 S.Ct. 350, 136 L.Ed.2d 288 (1996); Citizens Awareness Network, Inc. v. United [59]*59States Nuclear Regulatory Comm’n, 59 F.3d 284, 291 (1st Cir.1995); P.R. Sun Oil Co. v. ERA, 8 F.3d 73-77 (1st Cir.1993). While this case does not involve judicial review of either an agency adjudicatory proceeding nor of agency rulemaking, the requirement of adequate explanation is an inevitable consequence of applying the APA’s arbitrary and capricious standard to the Secretary’s reviewable decision whether to initiate prosecution. That requirement distinguishes this case from Heckler v. Chaney and its progeny. Chaney,. 470 U.S. at 834, 105 S.Ct. 1649 (comparing the presumption of nonreviewability of other agencies’ decisions not to undertake enforcement actions with the reviewability of the Secretary’s decision under the LMRDA).
The agency’s burden of explanation is heavier where an agency has expressed its statutory interpretation in regulations, adopted after notice-and-comment rule-making, and then seeks to depart from that interpretation. Agencies are bound by their regulations, and to permit what may be a change in the regulation without any explanation would undermine the requirement of notice-and-comment rule-making.11
Agencies do have leeway to change their interpretations of laws, as well as of their own regulations, provided they explain the reasons for such change and provided that those reasons meet the applicable standard of review. See Bowles v. Seminole Rock & Sand Co., 325 U.S. 410, 413-14, 65 S.Ct. 1215, 89 L.Ed. 1700 (1945) (counseling judicial deference to an agency’s interpretation of a rule it promulgates pursuant to statute). Compare Citizens Awareness Network, 59 F.3d at 291-92 (remanding to agency because agency altered interpretation of regulation without providing reasoning or following statutory procedures), with Pub. Interest Research Group v. FCC, 522 F.2d 1060, 1065 (1st Cir.1975) (upholding agency change in policy where agency provided a sufficiently clear explanation). Judicial deference to agency interpretations and policy choices is, in part, premised on the notion that agencies have greater expertise in their area of specialty than do courts, and that they should have flexibility to deal with changing economic and social realities. See, e,g., Chevron, U.S.A Inc. v. Natural Res. Def. Council, Inc., 467 U.S. 837, 863-66, 104 S.Ct. 2778, 81 L.Ed.2d 694 (1984). It is up to the agency in the first instance to interpret the statute and apply those interpretations to the facts.
Based on the Secretary’s Statement of Reasons, we are unable to determine if the Secretary has changed the policy articulated in 29 C.F.R. § 452.11 or her interpretation of that policy. We are confronted here with a different problem than was faced in Bachowski, created by what appears to be an inconsistency between the Secretary’s approach and her regulation and prior decisions, which may represent a volte-face by the Secretary. Her Statement of Reasons fails to explain whether she is departing from her prior course and, if so, the reasons for the change.
Decisions about the proper meaning of LMRDA statutory terms, and the proper application of the Act’s mandate, are for the Secretary to make, so long as they do not contravene the Act. These decisions are not up to the courts; thus, it is more appropriate for us to refrain from taking any judicial view at this point on the un[60]*60derlying interpretive issues in this case. Respect for her authority requires a remand, rather than final court resolution of the issue now. Moreover, a finding that the Secretary has acted arbitrarily and capriciously as to the ultimate issue would be premature, as it is not clear on this record that the Secretary is in fact repudiating her prior interpretations here.
The paucity of explanation hinders judicial review, requiring a remand to the Secretary to reopen, thereby providing the Secretary an opportunity to better explain her position. Bachowski, 421 U.S. at 574, 95 S.Ct. 1851; Maine v. Civil Aeronautics Bd., 520 F.2d 1240, 1245 (1st Cir.1975) (remanding for further proceedings because “[t]here are internal inconsistencies and a failure to clearly articulate the standard being applied” in agency decision); see also Doyle v. Brock, 821 F.2d 778, 781 (D.C.Cir.1987); DeVito v. Shultz, 300 F.Supp. 381 (D.D.C.1969). As the Supreme Court long ago said:
[The] basis [for an administrative action] must be set forth with such clarity as to be understandable. It will not do for a court to be compelled to guess at the theory underlying the agency’s action; nor can a court be expected to chisel that which must be precise from what the agency has left vague and indecisive. In other words, [w]e must know what a decision means before the duty becomes ours to say whether it is right or wrong,
SEC v. Chenery Corp., 332 U.S. 194, 196-97, 67 S.Ct. 1575, 91 L.Ed. 1995 (1947) (internal quotation marks omitted); see Allentown Mack Sales & Serv., Inc. v. NLRB, 522 U.S. 359, 375, 118 S.Ct. 818, 139 L.Ed.2d 797 (1998) (“The evil of a decision that applies a standard other than the one it enunciates spreads in both directions, preventing both consistent application of the law by subordinate agency personnel ... and effective review of the law by courts”) The Secretary is already committed by statute to expending resources in this area and has presumably reviewed all the pertinent factual materials presented. It is not a significant burden on her resources to ask her to explain her decision in a more reasoned fashion.12 Nor do we disrupt anything by vacating her decision; vacation is a proper remedy when an agency fails to explain its reasoning adequately. See Edward S. Quirk Co. v. NLRB, 241 F.3d 41 (1st Cir.2001) (vacating and remanding for further proceedings in absence of reasoned explanation from the Board); Gailius v. INS, 147 F.3d 34, 38 (1st Cir.1998) (vacation and remand appropriate where agency failed to give adequate explanation for conclusions); see generally Prestes, Remanding Without Vacating Agency Action, 32 Seton Hall L.Rev. 108 (forthcoming 2001), working paper available at http://papers.ssrn.com (criticizing the practice of remanding without vacating).
Should she again decide not to initiate suit, the Secretary must file a sufficient Statement of Reasons, which addresses both the application of the functions and purposes test of 29 C.F.R. § 452.11, and whether her decision is consistent with her [61]*61precedents. If there has been a change, she should also explain whether changing labor market economics justify a modification of prior interpretation or a building construction trades exception to it, or what the other reasons for the change are. See Yueh-Shaio Yang, 519 U.S. at 31-32, 117 S.Ct. 350 (agency may carve out exceptions to general policy).
We are mindful of the Supreme Court’s admonition that “endless litigation concerning the sufficiency of the written statement is inconsistent with the statute’s goal of expeditious resolution of post-election disputes.” Bachowski, 421 U.S. at 575, 95 S.Ct. 1851; see also Eskridge, Note, Dunlop v. Bachowski and the Limits of Judicial Review under Title TV of the LMRDA: A Proposal for Administrative Reform, 86 Yale L.J. 885, 890-96 (1977) (arguing that protracted judicial review impairs enforcement scheme). Nonetheless, a remand is the appropriate remedy here. A serious question has been raised about the Secretary’s adherence to her own articulated policies. Any delay and uncertainty occasioned by remand is justified by the need for clarity, both in this case and more generally, as to her present interpretation of her statutory obligations. Pension Benefit Guar. Corp. v. LTV Corp., 496 U.S. 633, 110 S.Ct. 2668, 110 L.Ed.2d 579 (1990).
The district court’s dismissal of the petition for review is reversed, the Statement of Reasons is vacated, and the matter is remanded to the district court with instructions to remand to the Secretary for proceedings consistent with this opinion.
So ordered.