There are two issues before us: whether a United States Postal Service (“Postal Service”) regulation that prohibits the employment of temporary resident aliens violates the unlawful discrimination provision of the Immigration Reform and Control Act of 1986 *1272(“IRCA”), and whether the Postal Service exceeded its authority under the Postal Reorganization Act of 1970 (“Act”) in promulgating the regulation. The administrative law judge (“ALJ”) from the Executive Office for Immigration Review at the Department of Justice granted summary judgment for the Postal Service, holding that its refusal to hire Olimpia Tovar, a temporary resident alien, did not constitute unlawful discrimination because the regulation fell within a statutory exemption to the anti-discrimination provision of IRCA; he also held that the Postal Service did not exceed its grant of authority under the Act in promulgating the regulation. Tovar disputes both aspects of the ruling, and also challenges the regulation on fifth amendment due process and equal protection grounds. (Tovar raised the constitutional issues before the ALJ, who declined to decide them because they concerned a regulation not issued by his own agency.) We agree with the ALJ’s holding that the regulation falls within a statutory exemption of IRCA. We reverse the ALJ’s grant of summary judgment, however, for further proceedings with respect to the question whether the Postal Service exceeded its authority under the Postal Reorganization Act of 1970. Because we decide the case on statutory grounds, we do not reach Tovar’s constitutional claims.1
I
Olimpia Tovar entered the United States unlawfully at some time prior to 1982. She obtained a temporary resident card on March 24, 1988, under the amnesty provision of the Immigration Relief and Control Act of 1986 (“IRCA”), Pub.L. 99-603, Title II, § 201(a), 100 Stat. 3394 (1986) (codified as amended at 8 U.S.C. § 1255a(a) (1988)). In January, 1989, Tovar applied for employment with the United States Postal Service (“Postal Service”) and took an examination. On April 27, 1989, she filed a declaration of intent to become a United States citizen — a preeondition under IRCA for eventual adjustment to permanent resident alien status. 8 U.S.C. § 1255a(b)(1)(D). On April 28, 1989, Tovar received notice from the Postal Service of her eligibility for the position of flat sorting machine operator. During her orientation for the new position, however, the Postal Service informed Tovar that she was not eligible for employment because she had not yet achieved permanent resident alien status. Under Postal Regulation 312.21, only those non-citizens who have been granted permanent resident alien status are eligible for employment with the Postal Service. It is the validity of that regulation that is at issue here.
As authorized by IRCA, Tovar filed a complaint of unfair immigration-related employment practices against the Postal Service in the Office of the Chief Administrative Hearing Officer (“OCAHO”). 8 U.S.C. § 1324b(d)(2). She alleged that Regulation 312.21 violated the anti-discrimination provision of IRCA, which provides:
It is an unfair immigration-related employment practice for a person or other entity to discriminate against any individual ... with respect to the hiring, or recruitment or referral for a fee, of the individual for employment or the discharging of the individual from employment—
(B) in the case of a protected individual (as defined in paragraph (3)), because of such individual’s citizenship status.
Id. § 1324b(a)(1). It is undisputed that To-var, an alien lawfully admitted for temporary residence pursuant to § 1255a(a), is a “protected individual” under IRCA. Id. § 1324b(a)(3).
Believing that no factual issues relating to Tovar’s claim were in dispute, the parties filed cross-motions for summary judgment. Tovar charged that Regulation 312.21 constituted unlawful discrimination under § 1324b(a)(l) and exceeded the authority of *1273the Postal Service as defined in the Postal Reorganization Act of 1970, Pub.L. 91-375, 84 Stat. 719 (codified as amended at 39 U.S.C. § 101 et seq.).2 The Postal Service argued, in response, that the regulation fell within a statutory exemption to § 1324b(a)(1), which reads as follows: Paragraph (1) shall not apply to—
(C) discrimination because of citizenship status which is otherwise required in order to comply with law, regulation, or executive order, or required by Federal, State, or local government contract, or which the Attorney General determines to be essential for an employer to do business with an agency or department of the Federal, State, or local government.
8 U.S.C. § 1324b(a)(2) (emphasis added). It further maintained that the regulation was a valid exercise of its authority to promulgate policies and regulations regarding eligibility for employment.
The administrative law judge (“ALJ”) concluded that Regulation 312.21 fell within the exemption provided in § 1324b(a)(2)(C) and that in adopting it the Postal Service did not exceed its statutory authority. Accordingly, the ALJ granted the motion of the Postal Service for summary judgment and dismissed Tovar’s complaint. As authorized by 8 U.S.C. § 1324b(i), Tovar appealed the ALJ’s decision to this court. On appeal, she emphasizes that she challenges the Postal Service’s regulation only as it applies to temporary residents under IRCA.3 We note that the class of temporary residents is self-exhausting, and that the time for filing any complaint regarding employment discrimination while in such status has already run.4
Since the ALJ issued his decision, Tovar has been accorded permanent resident alien status. However, because she seeks back pay for the period of time during which she was1 considered ineligible for employment with the Postal Service, this case is not moot.
II
Tovar contends, first, that the ALJ erred in concluding that employment decisions made under Regulation 312.21 are exempt from the anti-discrimination provision of IRCA. The plain language of the statutory exemption invoked by the Postal Service defeats her argument. Moreover, the legislative history of IRCA indicates that the anti-discrimination provision was designed primarily to prevent discrimination on the basis of alienage by private employers, rather than by the federal government.
*1274In § 1324b(a)(2)(C) of IRCA, quoted above, Congress expressly exempted employment discrimination that is mandated by federal law from the reach of the statutory anti-discrimination provision. The language of the exemption could hardly be clearer. Section 1324b(a)(1) does not apply to “discrimination because of citizenship status which is otherwise required in order to comply with ... regulation.” The refusal of the Postal Service to hire Tovar was based on its regulation, which provides that only citizens and permanent resident aliens are eligible for such employment. Accordingly, its refusal could not, as a matter of law, violate § 1324b(a)(1).
Tovar argues that treating the Postal Service regulation as exempt under § 1324b(a)(2)(C) would contravene congressional intent as expressed in the overall statutory scheme of IRCA and in the legislative history of the statute. Ordinarily, where a statute is clear on its face and “no further interpretive assistance is required.... it is proper to look only to the statute’s plain language.” Mt. Graham Red Squirrel v. Madigan, 954 F.2d 1441, 1453 (9th Cir.1992). However, where the language of the statute is uncertain or ambiguous, id. or “where a literal interpretation would thwart the purpose of the over-all statutory scheme or lead to an absurd result,” Wilshire Westwood Assoc. v. Atlantic Richfield Corp., 881 F.2d 801, 804 (9th Cir.1989) (internal quotation omitted; citation omitted), it may be proper to consider the statute in light of the relevant legislative history. Mt. Graham Red Squirrel, 954 F.2d at 1453. We find nothing contrary to an express or implied congressional intent in the interpretation mandated by the plain words of the statute; nor is the result “absurd.”
The language of the statutory exemptions to § 1324b(a)(l) demonstrates that Congress intended to allow public employers wide latitude with respect to the anti-discrimination provision of IRCA — latitude that Congress did not extend to private employers. Section 1324b(a)(2)(A), the private sector exemption, excuses only “person[s] or other entities] that employ[] three or fewer employees” from the requirements of § 1324b(a)(1). By contrast, § 1324b(a)(2)(C) releases from the constraints of § 1324b(a)(1) all federal, state, and local government employers who have adopted a regulation that mandates discrimination based on alienage. (The remaining statutory exemption, § 1324b(2)(B), which exempts discrimination on the basis of national origin that is exempt under Title VII of the Civil Rights Act, 42 U.S.C. § 2000e-2, functions purely as a conforming provision.) The effect of § 1324b(a)(2)(A) and § 1324b(a)(2)(C) is to apply the anti-discrimination provision of IRCA rigidly to all private employers virtually without exception, but to apply it only to those public employers who have not adopted contravening regulations. We conclude that in enacting these sections, Congress has indicated its intention to exempt regulations like the one at issue here from the anti-discrimination provision of IRCA.
For historical purposes, we note that the legislative history of IRCA supports our understanding of Congress’ intent. That history reveals that Congress included § 1324b in IRCA out of fear that the newly-instituted penalties for hiring illegal immigrants might induce private employers to discriminate against all individuals who sound or appear “foreign.” H.R.Rep. No. 682(1), 99th Cong., 2d Sess. 68, reprinted in 1986 U.S.C.C.A.N. 5649, 5653, see 8 U.S.C. § 1324a(e)(f). Congress was concerned with forestalling any future employment discrimination that might occur as a reaction to IRCA, not with restricting the authority of the federal government to establish criteria for federal employment. Our holding that the discrimination that Tovar complains of is beyond the reach of § 1324b(a)(1) therefore does not thwart the statutory scheme or produce a result contrary to that intended by Congress. Tovar’s first argument fails.
Ill
In the alternative, Tovar argues that Regulation 312.21 is invalid because, in promulgating the regulation, the Postal Service exceeded the authority conferred on it by the Postal Reorganization Act of 1970, 39 U.S.C. § 101 et seq. (the Act). In essence, her *1275argument is that the regulation is arbitrary, unreasonable, and contrary to law.
Under the Act, the Postal Service possesses “the right ... to hire, promote, transfer, assign, and retain officers and employees in positions within the Postal Service.” 39 U.S.C. § 1001(e)(2) (1980). In a section captioned “Postal Policy,” the Act further states that the Postal Service “shall provide prompt, reliable, and efficient services to patrons in all areas.” Id,., § 101(a).5 The Act empowers the agency to “adopt, amend, and repeal such rules and regulations as it deems necessary to accomplish the objectives of this title.” Id., § 401(2).
The Postal Service argues that Regulation 312.21 is within its statutory grant of authority because its governing statute permits it to adopt regulations that promote efficiency. It contends that the Regulation 312.21 heightens efficiency in three ways: it increases the likelihood that the persons the agency hires will become career employees, streamlines a cumbersome process by ridding the agency of the burden of tracking temporary resident employees through the amnesty process to ensure that they attain permanent residency, and reduces the pool of applicants seeking jobs with the Postal Service. We consider these contentions below.
A.
Before turning to the justifications the Postal Service offers in support of Regulation 312.21, we consider the legal status of the persons whom the regulation excludes from employment — temporary residents under IRCA. The Postal Service refuses to hire temporary residents, although it does employ non-citizens once they have achieved permanent residence under IRCA.6 The agency argues that it is justified in distinguishing between the two classes. We conclude that the record does not support summary judgment for the agency on that question.
To become a temporary resident, an alien must timely apply for temporary residence, 8 U.S.C. § 1255a(a)(1)(A),7 and must establish both continuous unlawful residence in the United States since January 1, 1982, id. § 1255a(a)(2)(A), and continuous physical presence in the United States since November 6, 1986, id., § 1255a(a)(3)(A). The alien must demonstrate that he or she
is admissible to the United States as an immigrant, ... has not been convicted of any felony or of three or more misdemeanors committed in the United States, ... has not assisted in the persecution of any person or persons on account of race, religion, nationality, membership in a particular social group, or political opinion, and ... is registered or registering under the Military Selective Service Act ... if the alien is required to be so registered under that Act.
Id., § 1255a(a)(4).
After eighteen months as a temporary resident, the alien may apply for permanent residency. 8 U.S.C. 1255a(b)(1)(A). There is only one additional requirement that she must meet to become a permanent resident, in addition to filing an application for such status within two years of the time she becomes eligible to do so, 8 U.S.C. § 1255a(b)(1)(A). She must demonstrate either a “minimal understanding of ordinary English and a knowledge and understanding of the history and government of the United States,” or the satisfactory pursuit of a course of study recognized by the Attorney General to achieve those goals. Id., § 1255a(b)(1)(D)(i). As counsel for the Postal Service conceded at oral argument, all employees of the Postal Service must demon*1276strate a knowledge of English. Therefore, any temporary resident who would be eligible for employment at the Postal Service but for her immigration status would have to meet this part of the requirement in any event. For an English-speaking person, demonstrating a knowledge of basic civics is not an onerous task, and the Postal Service does not suggest otherwise.
Thus, for a temporary resident who, except for immigration status, is qualified for employment with the Postal Service, the transition from temporary to permanent resident is almost automatic. The difference between the two classes is minimal. Even the Postal Service characterizes as “simple” the requirements for adjusting one’s status under IRCA from temporary to permanent resident. With this in mind, we turn to the standard under which we review the Postal Service regulation at issue in this case, and the agency’s justifications for hiring permanent residents while refusing to hire temporary residents.
B.
Since the Supreme Court’s decision in Chevron, U.S.A., Inc. v. Natural Resources Defense Council, Inc., 467 U.S. 837, 104 S.Ct. 2778, 81 L.Ed.2d 694 (1984), we have generally reviewed agency regulations under the standard set forth in that case. In applying Chevron, we first consider whether Congress has clearly expressed its opinion on an issue of statutory interpretation. If it has not, the only question remaining for a reviewing court is “whether the agency’s answer is based on a permissible construction of the statute.” Id., 467 U.S. at 842-43, 104 S.Ct. at 2781-82 (footnote omitted). In determining whether an agency’s construction is permissible, the court considers whether Congress has explicitly instructed the agency to flesh out specific provisions of the general legislation, or has impliedly left to the agency the task of developing standards to carry out the general policy of the statute. In the former case, a reviewing court must find the agency’s construction permissible unless it is arbitrary, capricious, or manifestly contrary to the statute; in the latter, a court must uphold the agency’s construction if it is reasonable. Id., 467 U.S. at 843-44, 104 S.Ct. at 2782.
Regulation 312.21 does not fit neatly into the Chevron framework. The language of Chevron itself speaks of an agency’s “construction” or “interpretation” of a statute. 467 U.S. at 843-44, 104 S.Ct. at 2782. Regulation 312.21 is not a construction or an interpretation of a statute; it is an exercise of authority pursuant to a statute. Further, Chevron generally applies to implementing regulations that agencies have promulgated within their area of expertise. The principle of deference to the exercise of administrative authority is derived from courts’ recognition that agencies possess a body of knowledge that uniquely suits them to accommodate conflicting policies concerning matters within their own area of skill and mastery. Id., 467 U.S. at 844-45, 104 S.Ct. at 2782-83. Neither party in the case before us contends that the Postal Service is singularly qualified in matters of immigration or employment law. Certainly, it has no expertise with respect to the question whether temporary residents under IRCA are more or less likely to be effective employees than permanent residents under that statute. Nor does the Act suggest any such special competence: as its provisions indicate, supra, the Postal Service’s area of expertise is delivering the mail. Whether temporary resident aliens under IRCA would perform less satisfactorily than permanent residents is a question not closely related to the agency’s essential competence.
Nevertheless, though the fit is inexact, we follow the Chevron model. We do so rather than create yet another standard of review. Applying the general Chevron principles to the regulation, we find that we are faced with a statute that is silent on the subject of the Postal Service’s authority to exclude temporary resident aliens from employment. Thus, Congress has manifested no intent on the issue. Nor does the Act instruct the Postal Service to promulgate regulations concerning the citizenship of its employees. Therefore, we analyze Regulation 312.21 as if it were the result of an implicit directive to the agency to develop the criteria under which Postal Service employees shall be hired. Accordingly, we must uphold the reg*1277ulation if it is “reasonable.” We apply this standard essentially because the agency is authorized to develop policies not involving the construction or interpretation of the statute it administers and not within its special area of competence. Reviewing such policies under a reasonableness standard permits courts to check improper agency actions, and at the same time ensures a sufficient degree of deference to the agency’s judgments.8
It is prudent to apply the reasonableness standard, the least deferential standard under Chevron, to Regulation 312.21 for another reason as well. Regulation 312.21 is not a “regulation” in the sense contemplated by Chevron. It is a regulation because a regulation declares it to be a regulation: according to the Postal Service, it is a regulation because 39 C.F.R. § 211.2(a) classifies it as such. That section provides:
The regulations of the Postal Service consist of:
(3) Headquarters Circulars, Management Instructions, Regional Instructions, handbooks, delegations of authority, and other regulatory issuances and directives of the Postal Service or the former Post Office Department. Any of the foregoing may be published in the FEDERAL REGISTER and the Code of Federal Regulations.
39 C.F.R. § 211.2(a)(3) (“§ 211.2(a)(3)”).9 There is, of course, no opportunity for public comment in the ease of a regulation adopted in this fashion.10 While courts, including ours, have treated regulations promulgated pursuant to § 211.2 just as they would any other regulations,11 in no such case has a Chevron analysis been undertaken, and in none has the validity of a regulation been at issue.12 Our review under Chevron’s reasonableness standard does not require us to uphold the Postal Service’s regulation if it is merely plausible. The reasonableness standard affords courts wider latitude than the arbitrary and capricious standard. It requires, inter alia, that the link between a regulation and a legitimate purpose it is intended to advance demonstrate more than “the minimum rationality a statute must bear in order to withstand analysis under the Due Process Clause.” Bowen v. Am. Hosp. Ass’n, 476 U.S. 610, 627, 106 S.Ct. 2101, 2112, 90 L.Ed.2d 584 (1986) (plurality opinion) (quoting Motor Vehicle Mfrs’ Ass’n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 43 n. 9, 103 S.Ct. 2856, 2866 n. 9, 77 L.Ed.2d 443 (1983)). However, we need not discuss the *1278nature of our inquiry further. For summary judgment purposes, the Postal Service’s regulation fails the reasonableness test completely.
C.
On appeal from summary judgment we consider whether there is any “genuine issue of material fact” and whether the moving party is entitled to judgment as a matter of law. Fed.R.Civ.P. 56(c). To defeat the government’s motion for summary judgment where the government made no factual showing as to the reasonableness of a regulation at issue, Tovar needed only to demonstrate that the regulation was facially discriminatory or that it operatéd in a discriminatory manner. In fact, all that a plaintiff is required to show in such a ease is that a genuine issue of material fact exists as to the discriminatory nature of the regulation at issue. In the face of such a showing, the government cannot prevail by relying on the regulatory language exclusively or by merely offering factually unsupported explanations. If a regulation is facially discriminatory or there is evidence that it operates in a discriminatory fashion, the government is obligated, at a minimum, to offer concrete, evi-dentiary facts that explain why the regulation is nevertheless reasonable. Conclusory statements are insufficient.
Here, the ALJ specifically found that the Postal Service’s regulation was facially discriminatory because it created a barrier to employment based on group status, ie. temporary residency. He also found that Tovar was denied employment not because she was personally unqualified but because she belonged to the disfavored class of temporary residents. Thus, there is no question that some evidence existed to support Tovar’s claim that Regulation 312.21 was unreasonable. The Postal Service could not stand silent in the face of these facts, but was required to offer specific evidence to show that its regulation was reasonable. See Pruitt v. Cheney, 963 F.2d 1160, 1165-66 (9th Cir.1992) (government must establish in the record its justification for the rationality of its group-status regulation), cert. denied, — U.S. -, 113 S.Ct. 655, 121 L.Ed.2d 581 (1992); High Tech Gays v. Defense Indus. Sec. Clearance Office, 895 F.2d 563, 575-77 (9th Cir.1990) (government must show a rational basis for its policy by establishing a rational relationship between its group-status policy and a legitimate governmental interest).13
As explained below, in this case the Postal Service has failed to offer any facts that would enable us to examine the link between the policy established by its facially discriminatory regulation and a legitimate purpose that the regulation is intended to advance. Instead, it offers conclusory and wholly unsupported generalizations that do not permit us to evaluate its claims.14 We note also that the Postal Service has sole possession of the facts necessary to prove that its regulation promotes “efficiency.” Under all of these circumstances, the Postal Service is not entitled to summary judgment.
Even if we did not believe that it was the Postal Service’s responsibility to offer facts that show that Regulation 312.21 is reasonable, we would nevertheless reverse the award of summary judgment. In a case such as this, an appellate court may, in the interests of sound judicial administration, vacate a summary judgment without reaching the merits of the issue presented if the record has not been sufficiently developed to allow for a fully informed decision. Kennedy v. Silas Mason Co., 334 U.S. 249, 256-57, 68 S.Ct. 1031, 1034, 92 L.Ed. 1347 (1948); Anderson v. Hodel, 899 F.2d 766, 770-71 (9th Cir.1990); see also William Schwarzer, Summary Judgment Under the Federal Rules: Defining Genuine Issues of Material Fact, *127999 F.R.D. 465, 475 (1984). In Anderson we vacated a summary judgment order that held that the governmental conduct there at issue was lawful, precisely because the record was insufficient to allow us to review the propriety of that conduct. 899 F.2d at 770-71. In Kennedy the Supreme Court declined to construe the Fair Labor Standards Act because the record created before the trial court at summary judgment was inadequate, and remanded the case for creation of an adequate record. 334 U.S. at 256-57, 68 S.Ct. at 1034.
We believe that the above principle applies with equal force to this case. While the regulation challenged here may not be as far-reaching or complex as the governmental actions at issue in Anderson or Kennedy, the salient question in each case is whether there is a sufficient factual record to allow the appellate court to decide the case before it. As Judge Schwarzer has aptly observed in his landmark article on summary judgment, “[T]he appellate court, if it concludes that a critical issue of ultimate fact has not been sufficiently developed and considered, should remand for that purpose.” 99 F.R.D. at 475.
Here, we are faced with a challenge to the reasonableness of an important agency regulation, but have not been given a factual foundation that would permit us to render a decision as to the regulation’s lawfulness. Where a challenge is made to the legitimacy of a sensitive governmental act, particularly one that deprives an individual of equal access to a public benefit, it is especially critical that the decisionmakers be provided with adequate information. If a regulation is erroneously upheld because of the absence of a sufficient factual record, an illegitimate exercise of governmental power will remain unchecked. On the other hand, if a regulation is struck down on the basis of inadequate information, then important governmental purposes may well be frustrated. The deci-sionmakers in such cases have a duty to ensure that their determinations are based upon an appropriate factual record. Because the ALJ in this case granted summary judgment without a proper factual record — i.e., a record sufficient to permit us to make the requisite evaluation of the reasonableness of the Postal Service’s regulation — we cannot affirm his order.
D.
The Postal Service offers several concluso-ry justifications for its challenged regulation. Its justifications may, in the end, prove to be correct. However, bare assertions or unsupported conclusions are not facts sufficient to support either a summary or a post-trial judgment. See MAI Sys. Corp. v. Peak Computer, Inc., 991 F.2d 511, 518 (9th Cir.1993). We now proceed to examine the government’s assertions and conclusions. Our analysis demonstrates why the grant of summary judgment was inappropriate in this case.
1. Career Employees
The Postal Service argues, first, that Regulation 312.21 heightens efficiency by increasing the likelihood that its employees will make their careers in the Postal Service. Temporary residents, it argues, might be deported after the Postal Service has gone to considerable expense to hire and train them. In support of its justification, the agency presents the declaration of Carol L. Booher, the Manager of the Selection Systems Administration Branch in the Employee Relations Department of the Postal Service.15 Booher is “responsible for the evaluation and implementation of all regulations relating to the selection of applicants for employment for the Postal Service.” Booher Declaration at ¶ 2. On the issue whether Regulation 312.21 increases the agency’s efficiency by *1280promoting its interest in hiring career employees, Booher stated,
the Postal Service ... determined [after reviewing Regulation 312.21] that based on its primary interest in career or permanent employees, the current policy sufficed to give all aliens opportunities once they qualify as permanent resident aliens while avoiding the potential loss of efficiency in hiring persons who do not ultimately qualify for permanent status and/or lose their clearance to work in the United States.
Id. at ¶ 9. Booher’s declaration here presents no facts, only a conclusion.
Booher’s declaration must be considered in light of the legal difference between temporary and permanent residence under IRCA. As explained above, the transition from temporary to permanent status is practically automatic. It does not require the alien to perform any task of any significance.16 If the adjustment required temporary residents to perform tasks that a number of them might be expected to fail, Booher’s declaration might be enough to warrant a grant of summary judgment. But, as the law stands, the adjustment in status requires virtually nothing. Booher does not allege any facts that tend to show that aliens are more likely to lose their authorization to work in the eighteen months before they become permanent residents than they are after they have been awarded permanent status — or that any temporary residents have ever done so. Nor does Booher’s declaration demonstrate that temporary residents are less likely than permanent residents to leave the Postal Service for other employment. It does not state that a significant number — or any number— of temporary residents who are eligible for permanent status have failed to achieve it. Certainly it does not state that temporary residents who otherwise qualify for employment at the Postal Service tend to fail to achieve permanent resident status. Figures from the INS — even preliminary ones — that show that temporary residents are more likely to lose their authorization to work in the United States than permanent residents, or that suggested that a significant number of temporary residents eligible for permanent status failed to achieve it, might, if unrebut-ted, have entitled the Postal Service to summary judgment. However, Booher’s wholly unsupported conclusion cannot provide adequate support for the Postal Service’s decision to promulgate Regulation 312.21. As a matter of law, the agency is not entitled to summary judgment on the basis of this justification.
2. Burden of Hiring and Tracking
The agency contends, next, that Regulation 312.21 streamlines an otherwise cumbersome application process. It argues that its efficiency would be undermined by the administrative burden of hiring temporary residents and of tracking their immigration status to ensure that they attained permanent residency. The agency’s second justification for Regulation 312.21 is no stronger than its first. Again, its sole support is Booher’s declaration, which states, in pertinent part,
As a result of the size of its operation, therefore, the Postal Service determined that the additional administrative burden of processing the additional paperwork required for temporary resident aliens ... as well as continuing "to track such persons to assure continued clearance to work was not warranted for the resulting addition to the applicant pool.
Booher Declaration at ¶ 8. There are no facts in this part of Booher’s declaration either, and it is based on one, if not two, erroneous legal assumptions.
As to the first part of the statement, it is silent regarding the extent or the nature of the administrative burden. Booher makes no factual assertion whatever regarding this alleged burden. Therefore, once again, the statement is wholly conclusory. More important, if we assume that Booher is referring to a burden that arises from an obligation to verify the status of temporary residents under IRCA that is different from the burden imposed with respect to permanent residents, naturalized citizens, or native-born cit*1281izens, she is simply wrong. To comply with IRCA, the Postal Service must verify, at the time an employee is hired, that the employee is authorized to work in the United States. 8 U.S.C. § 1324a(b). IRCA imposes that burden with respect to all employees, however. The Postal Service, like all other employers, must verify the authorization to work of every employee — temporary resident, permanent resident, naturalized or native-born citizen. Id. Therefore, hiring a temporary resident imposes no greater administrative burden on the Postal Service than hiring any other person. The number of employees will be the same, regardless of whether temporary residents are hired, and so will the burden of determining their eligibility to work.
As to the second part of Booher’s statement, the legal premise underlying her assertion regarding the tracking requirement is also incorrect. There is simply no tracking requirement. The law does not require an employer to verify an employee’s immigration status on a continuing basis, nor can the Postal Service point to any such requirement.17 The original verification is all that is required. Again, therefore, the argument is based on an erroneous legal assumption.18
Because there is no conceivable legal justification for the Postal Service’s rationale that 1) verifying the immigration status of temporary residents is more burdensome (or even imposes a different burden) than doing so for other employees, and that 2) it must track the immigration status of its employees, we cannot affirm summary judgment based upon this contention.19
S. Reduced Applicant Pool
Finally, the Postal Service argues that Regulation 312.21 increases efficiency by reducing the agency’s pool of potential employees. Once again, the agency’s only support for its justification is Booher’s declaration, which states that, if the Postal Service accepted temporary residents for employment,
[its employee] selection process would be substantially burdened administratively by broadening the alien selection policy. Such a policy would result in an increase in an applicant pool which was already larger than necessary while making [it] more difficult to administer a current postal [employee] selection system which is costly and complex in operation.... As a result of the size of its operation, ... the Postal Service determined that the additional administrative burden of processing the additional paperwork required for temporary resident aliens or other persons qualified to work in the United States ... was not warranted for the resulting addition to the applicant pool, particularly in light of the overwhelming abundance of applicants for postal positions. In fact, the Postal Service has actively explored methods for reducing the overall number of examinations given each year.
Booher Declaration at ¶¶ 5, 8. There are two separate answers with respect to this *1282purported rationale, each dispositive in its own way. First, a temporary resident under IRCA is eligible for permanent residence after completing an eighteen-month waiting period, and the change in status is virtually automatic.20 Booher does not explain why accepting applications for employment from persons while they are still in the initial status of temporary resident increases the pool any more than accepting their applications eighteen months later after they have become permanent residents. The question is simply one of timing, not of the extent of the burden. The pool will be larger one year and smaller another, with or without Regulation 312.21. The only question is: in which year will the pool be larger? The number of temporary residents under IRCA is finite. Thus, a fixed number of potential employees will be eligible to become part of that pool at one time or the other. Accordingly, Booher’s rationale simply falls flat of its own accord. In this respect also, the Postal Service has totally failed to advance a “reasonable” explanation for its regulation.
Second, even if the question were the size of the pool (and not the time at which the finite group becomes part of it), the Postal Service would still need to present some facts as to what the impact of these additional applicants would be. Booher says the additional applications would mean more paperwork. However, to evaluate the reasonableness of the regulation, we would have to have some idea of what that means. One additional sheet of paper, total, is more paperwork, but not enough more to make the regulation reasonable. We are unable to determine the nature of the burden — whether it is one percent more paperwork or fifty — because Boo-her’s declaration simply offers no facts.
E.
The Postal Service’s motion for summary judgment stands or falls on Booher’s declaration. However, that declaration presents only conclusory assertions with respect to two of the three asserted justifications for Regulation 312.21; as to the third, because of its erroneous legal assumptions, nothing would save the government. We hold that the declaration is insufficient to justify a grant of summary judgment in the agency’s favor. We emphasize that the agency could prevail on a motion for summary judgment if it offered sufficient facts to show that it is entitled to such relief as a matter of law. Valladolid v. Nat’l City, 976 F.2d 1293, 1295 (9th Cir.1992). However, for the reasons suggested above, it would undoubtedly have considerable difficulty in attempting to do so. In any event, on the record before us, the agency clearly has not made such a showing. Nor is the record otherwise sufficient to permit us to determine the reasonableness of the regulation.
IV.
In summary, we hold that Regulation 312.21 does not violate IRCA’s statutory bar on unlawful discrimination. However, given Tovar’s showing that the regulation served to preclude her employment based not on her individual qualifications but on her group status, we hold that the Postal Service has not offered sufficient facts to support a conclusion that, in adopting the regulation, it acted within its authority under the Postal Reorganization Act. Moreover, in light of the undeveloped state of the factual record, we are unable to conduct a proper review of the lawfulness of the Postal Service’s regulation. Therefore, the ALJ erred in granting summary judgment. Accordingly, we must vacate and remand for further proceedings.
AFFIRMED IN PART, REVERSED IN PART, AND REMANDED.
. We have jurisdiction over Tovar's statutory claims under 8 U.S.C. § 1324b(i). With respect to the constitutional issues, the record is inadequate. Without an appropriate record, we are unable to assess the strength of the government's interests. We express no view as to how Tovar should have proceeded with respect to her constitutional claims. We note, however, that the record to be made on remand will likely provide a sufficient basis for deciding the constitutional as well as the statutory issues, should it become necessary for us to do so.
. She also contended that the regulation violated her fifth amendment rights to procedural due process and equal protection of the law. The ALJ declined to rule on Tovar's constitutional claims on the ground that they concerned a regulation not issued by his own agency. We do not reach her constitutional claims. See supra note 1 and accompanying text.
. In her reply brief on appeal, Tovar presented statistics, apparently compiled by the INS, that showed, she contended, that temporary residents almost invariably succeed in becoming permanent residents. An affidavit in which Tovar’s counsel declared that the INS was the source of the statistics accompanied the information. To-var offered the statistics to buttress her contention that the justification advanced by the Postal Service to support the regulation at issue in this case lacks merit, and thus that in promulgating the regulation, the Postal Service exceeded its statutory authority.
The Postal Service moved to strike Tovar's reply brief, arguing that the new information was outside the record and that including it in a reply brief deprived the Postal Service of an opportunity to respond. To the extent that the brief presents new information, it is improper. Therefore, the following portions of the brief are ordered stricken: page 7, lines 10-23; page 7, line 25-page 8, line 1; page 8, lines 11-28; and tab 4.
.Under the terms of IRCA, to qualify for temporary residence, an alien must, inter alia, register for temporary residency by May 4, 1988, 8 U.S.C. § 1255a(a)(1)(A), 8 C.F.R. § 245a.2(a). The period of temporary residence is brief: under 8 U.S.C. § 1255a(b)(1)(A), all temporary residents must apply for permanent residence no more than three-and-a-half years after being accorded temporary resident status. The consequence of failing to apply for permanent resident status is termination of temporary resident status. 8 U.S.C. § 1255a(b)(2)(C). Thus, under IRCA, all temporary residents must have applied for permanent status no later than November 4, 1991. An alien who wishes to file a complaint regarding unfair immigration-related employment practices must do so within six months of the occurrence of the conduct complained of, 8 U.S.C. § 1324b(d)(3), and appeal from the disposition of such a complaint must be taken within sixty days after the entry of the disposition. Id., § 1324b(i)(1).
.This provision is reiterated in 39 U.S.C. § 101(e), which provides that "[i]n determining all policies for postal services, the Postal Service shall give the highest consideration to the requirement for the most expeditious collection, transportation, and delivery of important letter mail,” and in 39 U.S.C. § 403, "General Duties,” which provides, in part: “The Postal Service shall plan, develop, promote, and provide adequate and efficient postal services at fair and reasonable rates and fees."
. The agency refused to employ Tovar when she was a temporary resident under IRCA, but employs her now that she is a permanent resident under that statute.
. As noted above, the period to apply for temporary residence expired on May 4, 1988. 8 C.F.R. § 245a.2(a).
. The Postal Service contends that its hiring practices constitute a matter of policy and that the legislative history of the Act shows that Congress intended to give it the authority to make broad policy decisions. The agency asserts that if we hold that it has authority to make only decisions relating to day-to-day operations, we will open the door to a prolonged course of litigation over what constitutes a decision regarding policy as opposed to a decision regarding day-to-day operations. We agree that the Postal Service has the authority to adopt policies regulating hiring practices. However, that simply leads us to the question of the standard under which we review its adoption of such policies. It is that question we have addressed in the text accompanying this note.
. 39 C.F.R. § 211(a) was first adopted in 1973. 38 Fed.Reg. 20402 (1973).
. In any event, Regulation 312.21 is exempt from the notice and comment provisions of the Administrative Procedure Act. 5 U.S.C. § 553(a)(2) (notice and comment provisions do not apply to matters relating to agency personnel).
. See, e.g., Wood v. Merit Systems Protection Board, 938 F.2d 1280, 1282 (Fed.Cir.1991) (regarding a regulation found in a section of the Postal Service Employee and Labor Relations Manual); United States v. Pittsburg, 661 F.2d 783, 785 n. 1 (9th Cir.1981) (finding that a regulation adopted pursuant to 39 C.F.R. § 211.2 preempts local law); Page v. Bolger, 645 F.2d 227, 235 & n. 10 (4th Cir.1981), cert. denied, 454 U.S. 892, 102 S.Ct. 388, 70 L.Ed.2d 206 (1981) (enforcing against the Postal Service a regulation regarding procedures for promotion that was adopted pursuant to § 211.2).
. We have held that employment handbooks, agency guidelines, departmental bulletins, and other materials similar to that in which Regulation 312.21 is found do not afford substantive rights to members of the public where such rules are intended for internal agency use only. See Multnomah Legal Services Workers Union v. Legal Services Corp., 936 F.2d 1547, 1554 (9th Cir.1991), and cases cited therein. The regulation before us is clearly intended for external as well as internal use. In any event, Tovar does not challenge the status of Regulation 312.21 as a regulation.
. The dissent suggests that the analysis here should be conducted under an even lower level of scrutiny than that employed in High Tech Gays and Pruitt, because this case involves an administrative rather than an equal protection challenge to the reasonableness of a regulation. That this is an administrative rather than a constitutional case, however, does not mean that in reviewing for reasonableness we apply a lower standard. Indeed, as noted above, Bowen requires us to subject a regulation to closer scrutiny in an administrative than in a constitutional case. 463 U.S. at 43 n. 9, 103 S.Ct. at 2866 n. 9.
. See infra Part III.D.
. Booher’s declaration is dated June, 1990. It is thus not contemporaneous with Regulation 312.21. Generally speaking, a reviewing court may consider only the justifications for a rule advanced by the agency at the time the rule was promulgated; it may not consider post hoc justifications. Camp v. Pitts, 411 U.S. 138, 142, 93 S.Ct. 1241, 1244, 36 L.Ed.2d 106 (1973). However, when a regulation is promulgated pursuant to an exception to the notice and comment requirements of the Administrative Procedures Act, 5 U.S.C. § 553, no contemporaneous record ordinarily exists. It is permissible under such circumstances to rely on post hoc justifications for the rule. Women Involved in Fann Economics v. United States Dep’t of Agric., 876 F.2d 994, 997-1000 (D.C.Cir.1989).
. It does require the applicant to exhibit a knowledge of English, but, explained above, so does employment at the Postal Service. Thus, for a temporary resident employed by the Postal Service, the adjustment to permanent resident is almost involuntary. See supra Part III.A.
. We realize that the class of aliens who are not permanent residents is not limited to the class of temporary residents under IRCA. It also includes, for example, applicants for asylum, applicants for citizenship or residency based on marriage to a citizen or permanent resident, and holders of student visas. However, the class of temporary residents at issue in this case is limited to those temporary residents under IRCA. Under IRCA, liability attaches only if the employer gains actual knowledge that his or her temporary resident employees have lost their authorization to work in the United States. 8 U.S.C. § 1324a(a)(2).
. At oral argument, counsel for the Postal Service offered an additional reason for the agency to track the immigration status of its employees: to ensure that it has hired career employees. However, it seems to us self-evident that the Postal Service need not track its employees to determine whether or not they will continue to work at the agency. Moreover, the post hoc rationalization of an agency's appellate counsel, advanced for the first time on appeal, is entitled to no deference. Martin v. Occupational Safety and Health Review Comm'n, 499 U.S. 144, 156-57, 111 S.Ct. 1171, 1179, 113 L.Ed.2d 117 (1991). In any event, counsel's suggestion, like the Booher declaration, is unsupported by any evidence that might assist us in evaluating the agency's decision.
.In any event, even if there were a legal justification for a verification and tracking policy, the Postal Service would still have to make some minimal factual showing as to the nature and extent of the burden imposed. None is, of course, offered.
. See supra Part III.A.