Mr. Justice Stevens
delivered the opinion of the Court.
The New York City Transit Authority refuses to employ persons who use methadone. The District Court found that this policy violates the Equal Protection Clause of the Fourteenth Amendment. In a subsequent opinion, the court also held that the policy violates Title VII of the Civil Rights Act of 1964. The Court of Appeals affirmed without reaching the statutory question. The departure by those courts from the procedure normally followed in addressing statutory and con[571] stitutional questions in the same case, as well as concern that the merits of these important questions had been decided erroneously, led us to grant certiorari.1 438 U. S. 904. We now reverse.
The Transit Authority (TA) operates the subway system and certain bus lines in New York City. It employs about 47,000 persons, of whom many — perhaps most — are employed in positions that involve danger to themselves or to the public. For example, some 12,300 are subway motormen, towermen, conductors, or bus operators. The District Court found that these jobs are attended by unusual hazards and must be performed by “persons of maximum alertness and competence.” 399 F. Supp. 1032, 1052 (SDNY 1975). Certain other jobs, such as operating cranes and handling high-voltage equipment, are also considered “critical” or “safety sensitive,” while still others, though classified as “noncritical,” have a potentially important impact on the overall operation of the transportation system.2
TA enforces a general policy against employing persons [572] who use narcotic drugs. The policy is reflected in Rule 11 (b) of TA’s Rules and Regulations.
“Employees must not use, or have in their possession, narcotics, tranquilizers, drugs of the Amphetamine group or barbiturate derivatives or paraphernalia used to administer narcotics or barbiturate derivatives, except with the written permission of the Medical Director — Chief Surgeon of the System.”
Methadone is regarded as a narcotic within the meaning of Rule 11 (b). No written permission has ever been given by TA's medical director for the employment of a person using methadone.3
[573] The District Court found that methadone is a synthetic narcotic and a central nervous system depressant. If injected into the bloodstream with a needle, it produces essentially the same effects as heroin.4 Methadone has been used legitimately in at least three ways — as a pain killer, in “detoxification units” of hospitals as an immediate means of taking addicts off of heroin,5 and in long-range “methadone maintenance programs” as part of an intended cure for heroin addiction. See 21 CNR § 310.304 (b) (1978). In such programs the methadone is taken orally in regular doses for a prolonged period. As so administered, it does not produce euphoria or any pleasurable effects associated with heroin; on the contrary, it prevents users from experiencing those effects [574] when they inject heroin, and also alleviates the severe and prolonged discomfort otherwise associated with an addict’s discontinuance of the use of heroin.
About 40,000 persons receive methadone maintenance treatment in New York City, of whom about 26,000 participate in the five major public or semipublic programs,6 and 14,000 are involved in about 25 private programs.7 The sole purpose of all these programs is to treat the addiction of persons who have been using heroin for at least two years.
Methadone maintenance treatment in New York is largely governed by regulations promulgated by the New York State Drug Abuse Control Commission. Under the regulations, the newly accepted addict must first be detoxified, normally in a hospital. A controlled daily dosage of methadone is then prescribed. The regulations require that six doses a week be administered at a clinic, while the seventh day’s dose may be taken at home. If progress is satisfactory for three months, additional doses may be taken away from the clinic, although [575] throughout most of the program, which often lasts for several years, there is a minimum requirement of three clinic appearances a week. During these visits, the patient not only receives his doses but is also counseled and tested for illicit use of drugs.8
The evidence indicates that methadone is an effective cure for the physical aspects of heroin addiction. But the District Court also found “that many persons attempting to overcome heroin addiction have psychological or life-style problems which reach beyond what can be cured by the physical taking of doses of methadone.” 399 F. Supp., at 1039. The crucial indicator of successful methadone maintenance is the patient’s abstinence from the illegal or excessive use of drugs and alcohol. The District Court found that the risk of reversion to drug or alcohol abuse declines dramatically after the first few months of treatment. Indeed, “the strong majority” of patients who have been on methadone maintenance for at least a year are free from illicit drug use.9 But a significant [576] number are not. On this critical point, the evidence relied upon by the District Court reveals that even among participants with more than 12 months’ tenure in methadone maintenance programs, the incidence of drug and alcohol abuse may often approach and even exceed 25%.10
This litigation was brought by the four respondents as a class action on behalf of all persons who have been, or would in the future be, subject to discharge or rejection as employees of TA by reason of participation in a methadone maintenance program. Two of the respondents are former employees of TA who were dismissed while they were receiving methadone treatment.11 The other two were refused employment by TA, one both shortly before and shortly after the successful conclusion of his methadone treatment,12 and the other while he [577] was taking methadone.13 Their complaint alleged that TA’s blanket exclusion of all former heroin addicts receiving methadone treatment was illegal under the Civil Rights Act of 1866, Rev. Stat. § 1977, 42 U. S. C. § 1981, Title VII of the Civil Rights Act of 1964, 78 Stat. 253, as amended, 42 U. S. C. § 2000e et seg., and the Equal Protection Clause of the Fourteenth Amendment.
The trial record contains extensive evidence concerning the success of methadone maintenance programs, the employ-ability of persons taking methadone, and the ability of prospective employers to detect drug abuse or other undesirable characteristics of methadone users. In general, the District Court concluded that there are substantial numbers of methadone users who are just as employable as other members of the general population and that normal personnel-screening procedures — at least if augmented by some method of obtaining information from the staffs of methadone programs — would enable TA to identify the unqualified applicants on an individual basis. 399 F. Supp., at 1048-1051. On the other hand, the District Court recognized that at least one-third of the persons receiving methadone treatment — and probably a good many more — would unquestionably be classified as unemployable.14
[578] After extensively reviewing the evidence, the District Court briefly stated its conclusion that TA’s methadone policy is unconstitutional. The conclusion rested on the legal proposition that a public entity “cannot bar persons from employment on the basis of criteria which have no rational relation to the demands of the jobs to be performed.” Id., at 1057. Because it is clear that substantial numbers of methadone users are capable of performing many of the jobs at TA, the court held that the Constitution will not tolerate a blanket exclusion of all users from all jobs.
The District Court enjoined TA from denying employment to any person solely because of participation in a methadone maintenance program. Recognizing, however, the special responsibility for public safety borne by certain TA employees and the correlation between longevity in a methadone maintenance program and performance capability, the injunction authorized TA to exclude methadone users from specific categories of safety-sensitive positions and also to condition eligibility on satisfactory performance in a methadone program for at least a year. In other words, the court held that TA could lawfully adopt general rules excluding all methadone users from some jobs and a large number of methadone users from all jobs.
Almost a year later the District Court filed a supplemental opinion allowing respondents to recover attorney’s fees under 42 U. S. C. § 2000e-5 (k). This determination was premised on the court’s additional holding that TA’s drug policy violated Title VII. Having already concluded that the blanket [579] exclusion was not rationally related to any business needs of TA, the court reasoned that the statute is violated if the exclusionary policy has a discriminatory effect against blacks and Hispanics. That effect was proved, in the District Court’s view, by two statistics: (1) of the employees referred to TA’s medical consultant for suspected violation of its drug policy, 81% are black or Hispanic; (2) between 62% and 65% of all methadone-maintained persons in New York City are black or Hispanic. 414 F. Supp. 277, 278-279 (SDNY 1976). The court, however, did not find that TA’s policy was motivated by any bias against blacks or Hispanics; indeed, it expressly found that the policy was not adopted with a discriminatory purpose. Id., at 279.
The Court of Appeals affirmed the District Court’s constitutional holding. 558 F. 2d 97. While it declined to reach the statutory issue, it also affirmed the award of attorney’s fees under the aegis of the recently enacted Civil Rights Attorney’s Fees Awards Act of 1976, 42 U. S. C. § 1988, which provides adequate support for an award of legal fees to a party prevailing on a constitutional claim.15
After we granted certiorari, Congress amended the Rehabilitation Act of 1973, 87 Stat. 357, 29 U. S. C. § 701 et seq., to prohibit discrimination against a class of “handicapped individuals” that arguably includes certain former drug abusers and certain current users of methadone. Pub. L. 95-602, 92 Stat. 2984. Respondents argue that the amendment now [580] mandates at least the prospective relief granted by the District Court and the Court of Appeals and that we should therefore dismiss the writ as improvidently granted. We are satisfied, however, that we should decide the constitutional question presented by the petition. Before doing so, we shall discuss (1) the effect of the Rehabilitation Act on this case; and (2) the error in the District Court's analysis of Title VII.
I
Respondents contend that the recent amendment to § 7 (6) of the Rehabilitation Act proscribes TA's enforcement of a general rule denying employment to methadone users.16 Even if respondents correctly interpret the amendment, and even if they have a right to enforce that interpretation,17 the case [581] is not moot since their claims arose even before the Act itself was passed,18 and they have been awarded monetary relief.19 Moreover, the language of the statute, even after its amendment, is not free of ambiguity,20 and no administrative or judicial opinions specifically considering the impact of the statute on methadone users have been called to our attention. Of greater importance, it is perfectly clear that however we might construe the Rehabilitation Act, the concerns that prompted our grant of certiorari would still merit our attention.21 We therefore decline to give the statute its first judicial construction at this stage of the litigation.
[582] II
Although respondents have consistently relied on both statutory and constitutional claims, the lower courts focused primarily on the latter. Thus, when the District Court decided the Title VII issue, it did so only as an afterthought in order to support an award of attorney's fees; the Court of Appeals did not even reach the Title VII issue. We do not condone this departure from settled federal practice. “If there is one doctrine more deeply rooted than any other in the process of constitutional adjudication, it is that we ought not to pass on questions of constitutionality . . . unless such adjudication is unavoidable.” Spector Motor Service, Inc. v. McLaughlin, 323 U. S. 101, 105. Before deciding the constitutional question, it was incumbent on those courts to consider whether the statutory grounds might be dispositive.22 What[583] ever their reasons for not doing so,23 we shall first dispose of the Title VII issue.24
The District Court’s findings do not support its conclusion [584] that TA’s regulation prohibiting the use of narcotics, or its interpretation of that regulation to encompass users of methadone, violated Title YII of the Civil Rights Act.
A prima facie violation of the Act may be established by statistical evidence showing that an employment practice has the effect of denying the members of one race equal access to employment opportunities. Even assuming that respondents have crossed this threshold, when the entire record is examined it is clear that the two statistics on which they and the District Court relied do not prove a violation of Title VII.25
First, the District Court noted that 81% of the employees referred to TA’s medical director for suspected violation of its narcotics rule were either black or Hispanic. But respondents [585] have only challenged the rule to the extent that it is construed to apply to methadone users, and that statistic tells us nothing about the racial composition of the employees suspected of using methadone.26 Nor does the record give us any information about the number of black, Hispanic, or white persons who were dismissed for using methadone.
Second, the District Court noted that about 63% of the persons in New York City receiving methadone maintenance in public programs — i. e., 63%- of the 65% of all New York City methadone users who are in such programs27 — are black or Hispanic. We do not know, however, how many of these persons ever worked or sought to work for TA. This statistic therefore reveals little if anything about the racial composition of the class of TA job applicants and employees receiving methadone treatment. More particularly, it tells us nothing about the class of otherwise-qualified applicants and employees who have participated in methadone maintenance [586] programs for over a year — the only class improperly excluded by TA’s policy under the District Court’s analysis. The record demonstrates, in fact, that the figure is virtually irrelevant because a substantial portion of the persons included in it are either unqualified for other reasons — such as the illicit use of drugs and alcohol28 — or have received successful assistance in finding jobs with employers other than TA.29 Finally, we have absolutely no data on the 14,000 methadone users in the private programs, leaving open the possibility that the percentage of blacks and Hispanics in the class of methadone users is not significantly greater than the percentage of those minorities in the general population of New York City.30
[587] At best, respondents’ statistical showing is weak; even if it is capable of establishing a prima facie case of discrimination, it is assuredly rebutted by TA’s demonstration that its narcotics rule (and the rule’s application to methadone users) is “job related.” 31 The District Court’s express finding that the rule was not motivated by racial animus forecloses any claim in rebuttal that it was merely a pretext for intentional discrimination. 414 F. Supp., at 279. We conclude that respondents failed to prove a violation of Title VII. We therefore must reach the constitutional issue.
Ill
The Equal Protection Clause of the Fourteenth Amendment provides that no State shall “deny to any person within its jurisdiction the equal protection of the laws.” The Clause announces a fundamental principle: the State must govern impartially. General rules that apply evenhandedly to all persons within the jurisdiction unquestionably comply with this principle. Only when a governmental unit adopts a rule that has a special impact on less than all the persons subject [588] to its jurisdiction does the question whether this principle is violated arise.
In this case, TA’s Rule 11 (b) places a meaningful restriction on all of its employees and job applicants; in that sense the rule is one of general applicability and satisfies the equal protection principle without further inquiry. The District Court, however, interpreted the rule as applicable to the limited class of persons who regularly use narcotic drugs, including methadone. As so interpreted, we are necessarily confronted with the question whether the rule reflects an impermissible bias against a special class.
Respondents have never questioned the validity of a special rule for all users of narcotics. Rather, they originally contended that persons receiving methadone should not be covered by that rule; in other words, they should not be included within a class that is otherwise unobjectionable. Their constitutional claim was that methadone users are entitled to be treated like most other employees and applicants rather than like other users of narcotics. But the District Court’s findings unequivocally establish that there are relevant differences between persons using methadone regularly and persons who use no narcotics of any kind.32
[589] Respondents no longer question the need, or at least the justification, for special rules for methadone users. Indeed, they vigorously defend the District Court’s opinion which expressly held that it would be permissible for TA to have a special rule denying methadone users any employment unless they had been undergoing treatment for at least a year, and another special rule denying even the most senior and reliable methadone users any of the more dangerous jobs in the system.
The constitutional defect in TA’s employment policies, according to the District Court, is not that TA has special rules for methadone users, but rather that some members of the class should have been exempted from some requirements of the special rules. Left intact by its holding are rules requiring special supervision of methadone users to detect evidence of drug abuse, and excluding them from high-risk employment. Accepting those rules, the District Court nonetheless concluded that employment in nonsensitive jobs could not be denied to methadone users who had progressed satisfactorily with their treatment for one year, and who, when examined individually, satisfied TA’s employment criteria. In short, having recognized that disparate treatment of methadone users simply because they are methadone users is permissible — and having excused TA from an across-the-board requirement of individual consideration of such persons — the District Court construed the Equal Protection Clause as requiring TA to adopt additional and more precise special rules for that special class.
[590] But any special rule short of total exclusion that TA might adopt is likely to be less precise — and will assuredly be more costly33 — than the one that it currently enforces. If eligibility is marked at any intermediate point — whether after one year of treatment or later — the classification will inevitably discriminate between employees or applicants equally or [591] almost equally apt to achieve full recovery.34 Even the District Court’s opinion did not rigidly specify one year as a constitutionally mandated measure of the period of treatment that guarantees full recovery from drug addiction.35 The uncertainties associated with the rehabilitation of heroin addicts precluded it from identifying any bright line marking the point at which the risk of regression ends.36 By contrast, the “no drugs” policy now enforced by TA is supported by the legitimate inference that as long as a treatment program (or other drug use) continues, a degree of uncertainty persists.37 Accordingly, an employment policy that postpones [592] eligibility until the treatment program has been completed, rather than accepting an intermediate point on an uncertain line, is rational. It is neither unprincipled nor invidious in the sense that it implies disrespect for the excluded subclass.
At its simplest, the District Court’s conclusion was that TA’s rule is broader than necessary to exclude those methadone users who are not actually qualified to work for TA. We may assume not only that this conclusion is correct but also that it is probably unwise for a large employer like TA to rely on a general rule instead of individualized consideration of every job applicant. But these assumptions concern matters of personnel policy that do not implicate the principle safeguarded by the Equal Protection Clause.38 As the District Court recognized, the special classification created by TA’s rule serves the general objectives of safety and efficiency.39 Moreover, the exclusionary line challenged by respondents “is not one which is directed 'against’ any individual or category of persons, but rather it represents a policy choice . . . made by that branch of Government vested with the power to make such choices.” Marshall v. United States, 414 U. S. 417, 428. [593] Because it does not circumscribe a class of persons characterized by some unpopular trait or affiliation, it does not create or reflect any special likelihood of bias on the part of the ruling majority.40 Under these circumstances, it is of no constitutipnal significance that the degree of rationality is not as great with respect to certain ill-defined subparts of the classification as it is with respect to the classification as a whole. Mathews v. Diaz, 426 U. S. 67, 83-84.41
[594] No matter how unwise it may be for TA to refuse employment to individual car cleaners, track repairmen, or bus-drivers simply because they are receiving methadone treatment, the Constitution does not authorize a federal court to interfere in that policy decision. The judgment of the Court of Appeals is
Reversed.
“Considerations governing review on certiorari
“1. A review on writ of certiorari is not a matter of right, but of sound judicial discretion, and will be granted only where there are special and important reasons therefor. The following, while neither controlling nor fully measuring the court’s discretion, indicate the character of reasons which wih be considered:
“(b) Where a court of appeals . . . has decided a federal question in a way in conflict with applicable decisions of this court; or has so far departed from the accepted and usual course of judicial proceedings, or so far sanctioned such a departure by a lower court, as to call for an exercise of this court’s power of supervision.”
Although it did not settle the question of what policy TA enforces in this respect, the District Court included former users in the plaintiff class. It then afforded them relief from any blanket exclusionary policy that TA might enforce, although, again, the supporting factual findings were admittedly “not [based on] a great deal” of evidence. Id., at 1051.
TA contends that the meager evidence received at trial on the “former users” issue was insufficient to support either the class or relief determinations made with respect to those persons. We go further. As far as we are aware there was no evidence offered at trial, and certainly none relied upon by the District Court, that TA actually refused employment to any former user entitled to relief under the injunction ordered by that court. (As we point out in n. 12, infra, the one named plaintiff, Frasier, who was a former user when the complaint was filed was clearly a current user at the time he first applied for a job with TA and may well have been properly perceived as a current user when he next applied, notwithstanding his assertion of successful completion during the intervening three weeks. In any case, he had not completed a full year of methadone maintenance and could therefore be excluded under the District Court’s injunction.)
It follows that neither the' findings of fact, nor the record evidence, squarely presents any issue with respect to former users that must be [573] resolved in order to dispose of this litigation. And, of course, it is those findings and that evidence, rather than statements of the parties on appeal and even offhand and clearly erroneous characterizations of the findings and evidence by the Court of Appeals, see opinion of MR. Justice Powell, post, at 594^595, that determine the issues properly before this Court. A policy excluding all former users would be harder to justify than a policy applicable only to persons currently receiving treatment. A court should not reach out to express an opinion on the constitutionality of such a policy unless necessary to adjudicate a concrete dispute between adverse litigants. We shall therefore confine our consideration to the legality of TA’s enforcement of its Rule 11 (b) against current users of methadone.
“(1) The Beth Israel program . . . with 35 clinics treating 7100 patients;
“(2) A program administered by the City of New York with 39 clinics treating 12,400 patients (hereafter referred to as ‘the City program’);
“(3) A program administered by the Bronx State Hospital and the Albert Einstein College of Medicine, with 7 clinics treating about 2400 patients;
“ (4) A program operated by the Addiction Research and Treatment Center (ARTC) with 6 clinics treating about 1200 patients; and
“(5) A program operated by the New York State Drug Abuse Control Commission (DACC), with 8 clinics treating about 1100 patients.
“The total number of patients treated in public or semi-public programs is about 26,000. It appears that these programs are financed almost entirely by federal, state and city funds.” Id., at 1040.
“Dr. Trigg of Beth Israel testified that about 5,000 out of the 6,500-7,000 patients in his clinics have been on methadone maintenance for a year or more. He further testified that 75% of this 5,000 are free from illicit drug use.” Id., at 1046.
Similarly, although the figures may be somewhat higher for the city and Bronx State Hospital programs, only 70% of the ARTC patients with a year’s tenure or more were found to be free from illicit drug or alcohol use. It is reasonable to infer from this evidence that anywhere from 20% to 30% of those who have been on maintenance for over a year have drug or alcohol problems.
“No otherwise qualified handicapped individual in the United States, as defined in section 706 (6) of this title, shall, solely by reason of his handicap, be excluded from the participation in, be denied the benefits of, or be subjected to discrimination under any program or activity receiving Federal financial assistance.”
It is stipulated that the TA receives federal financial assistance.
In relevant part, § 7 (6) of the Act, 29 U. S. C. § 706 (6), as amended and redesignated, 92 Stat. 2984, 29 U. S.- C. § 706 (7) (B) (1976 ed., Supp. Ill), provides:
“[T]he term ‘handicapped individual’ . . . means any person who (i) has a physical or mental impairment which substantially limits one or more of such person’s major life activities, (ii) has a record of such an impairment, or (iii) is regarded as having such an impairment. For purposes of sections 503 and 504 as such sections relate to employment, such term does not include any individual who is an alcoholic or drug abuser whose current use of alcohol or drugs prevents such individual from performing the duties of the job in question or whose employment, by reason of such current alcohol or drug abuse, would constitute a direct threat to property or the safety of others.”
“The policy, however, has not been limited to jurisdictional determinations. For, in addition, 'the Court [has] developed, for its own governance in the cases confessedly within its jurisdiction, a series of rules under which it has avoided passing upon a large part of all the constitutional questions pressed upon it for decision.’ Thus, as those rules were listed in support of the statement quoted, constitutional issues affecting legislation will not be determined in friendly, nonadversary proceedings; in advance of the necessity of deciding them; in broader terms than are required by the precise facts to which the ruling is to be applied; if the record presents some other ground upon which the case may be disposed of; at the instance of one who fails to show that he is injured by the statute’s operation, or who has availed himself of its benefits; or if a eon-[583] struction of the statute is fairly possible by which the question may be avoided.” Rescue Army v. Municipal Court, 331 U. S. 549, 568-569 (footnotes omitted), quoting Ashwander v. TVA, 297 U. S. 288, 346 (Brandeis, J., concurring).
Whatever the theoretical validity of respondents’ explanations for the actions of the District Court' and the Court of Appeals, the fact remains that we are forced to speculate about what motivated them because they never explained their haste to address a naked constitutional issue despite the presence in the case of alternative statutory theories. It also bears noting that in its second opinion the District Court did decide that TA’s policy violated a federal statute, and its decision, without addressing any constitutional issue, provided a statutory basis for virtually all of the relief that it ultimately awarded. Had it confronted the issue, therefore, it presumably would have concluded that it could have decided the case without addressing the constitutional issue on which it initially decided the ease.
From the time they filed their complaint until their submissions to this Court, respondents have relied on statistics to demonstrate the discriminatory effect of TA’s methadone policy. They have never attempted to present a discriminatory purpose case and would be hard pressed to do so in the face of the District Court’s explicit finding that no animus motivated TA in establishing its policy, 414 F. Supp. 277, 279 (SDNY 1976), and in the face of TA’s demonstration in forms filed with the Equal Employment Opportunity Commission that the percentage of blacks and Hispanics in its work force is well over twice that of the percentage in the work force in the New York metropolitan area.
Because of our conclusion on the merits of respondents’ Title VII claim, we need not address the constitutional challenge made by TA to Title VII insofar as it authorizes relief against a municipal agency under the circumstances of this case. See n. 23, supra.
“TA employees showing physical manifestations of drug abuse other than the definite presence of morphine or methadone or other illicit drug in the urine, are referred for consultation to [the medical director] . . . .” App. 86A (emphasis added).
In view of this stipulation and the District Court’s finding that few if any physical manifestations of drug abuse characterize methadone-maintained persons, 399 F. Supp., at 1042-1045, it seems likely that such persons would not be included in the statistical pool referred to by the District Court. It should also be noted that when the dissent refers to the rejection of almost 5% of all applicants “due to the rule,” post, at 600, the reference is to all narcotics users rather than to methadone users. The record does not tell us how many methadone users were rejected.
In addition, a substantial percentage of persons taking methadone will not successfully complete the treatment program. The findings do not indicate with any precision the number who drop out, or the number who can fairly be classified as unemployable, but the evidence indicates that it may well be a majority of those taking methadone at any given time. See nn. 14 and 28, supra.
“demonstrate that they have been on a reliable methadone program for a year or more; that they have faithfully abided by the rules of the program; [and] that, according to systematic tests and observations, they have been free of any illicit drug or alcohol abuse for the entire period of treatment, excluding a possible adjustment period . . . .” 399 F. Supp., at 1049.
The District Court also recognized that verifying the above demonstrations by the methadone user would require special efforts to obtain reliable information from, and about, each of the many different methadone maintenance clinics — a task that it recognized could be problematic in some cases. Id., at 1050; see n. 7, supra. Furthermore, once it hired a methadone user, TA would have a continuing duty to monitor his progress in the maintenance program and would have to take special precautions against his promotion to any of the safety-sensitive positions from which the District Court held he may be excluded.
The dissent is therefore repeatedly mistaken in attributing to the District Court a finding that TA’s “normal screening process without additional effort” would suffice in the absence of the “no drugs” rule. Post, at 608. See post, at 608 n. 14. Aggravating this erroneous factual assumption is a mistaken legal proposition advanced by the dissent — that TA can be faulted for failing to prove the unemployability of “successfully maintained methadone users. Post, at 605. Aside from the misallocation of the burden of proof that underlies this argument, it is important to note, see post, at 606, that TA did prove that 20% to 30% of the class afforded relief by the District Court are not “successfully maintained,” and hence are assuredly not employable. Even assuming therefore that the percentage of employable persons in the remaining 70% is the same as that in the class of TA applicants who do not use methadone, it is respondents who must be faulted for failing to prove that the offending 30% could be excluded as cheaply and effectively in the absence of the rule.