Opinion for the Court filed by Circuit Judge D.H. GINSBURG.
Assоciations representing fruit growers in several eastern states filed suit, on behalf of themselves and their members, challenging the Secretary of Labor’s interpretation of the regulation establishing the minimum wage for foreign agricultural (H-2) workers. A class of such workers intervened and counter-claimed for unpaid wages for the 1983 through 1985 harvests. Relying upon an earlier court decision interpreting the minimum wage regulation (in a case to which the growers were not parties), the district court precluded the growers from relitigating the meaning of the regulation. The district court also granted the workers’ claim for unpaid wages for the 1983 and 1985 harvests and denied the workers’ claim for the 1984 harvest. Although we follow a line of reasoning different in some respects from that of the district court, we uphold its judgment in all respects.
I. BackgRound
The H-2 program enables a U.S. employer to hire foreign agricultural workers for seasonal work. 8 U.S.C. § 1101(a)(15)(H)(ii) (1982) (amended and renamed “H-2A” after the events at issue here, see 8 U.S.C. § 1101(a)(15)(H)(ii)(a)). In order to hire H-2 workers, an employer must submit to the Secretary of Labor a “job clearance order” in which the employer promises to pay its H-2 workers at least the hourly “adverse effect wage rate” (AEWR) — an amount set by the Secretary in order to ensure that the H-2 program does not adversely affect “the wages of similarly employed U.S. workers,” 20 C.F.R. § 655.200(b) (1983) (current version at 20 C.F.R. § 655.200(c)). An employer that pays its workers by the piece rathеr than by the hour must establish a piece rate that allows a worker of average productivity to earn the AEWR. See id. § 655.202(b)(9)(ii) (amended 1987).
When the Secretary increases the AEWR, an employer that pays by the piece has two options: either increase the piece rate or increase the productivity of its average worker. In response to claims that *1267 employers were demanding greater output per worker hour, see 43 Fed.Reg. 10306, 10309 (1978), which would have a correspondingly “adverse effect” upon domestic agricultural workers, in 1978 the Secretary promulgated the following regulation:
In any year in which the applicable [AEWR] is increased, employers shall adjust their piece rates upward to avoid requiring a worker to increase his or her productivity over the previous year in order to earn an amount equal to what the worker would earn if the worker were paid at the [AEWR].
Id. at 10317 (codified at 20 C.F.R. § 655.-207(c); repealed 1987). In 1981, the Secretary interpreted the 1978 regulation to mean that when the Secretary increases the AEWR, an employer is required to increase its piece rate only if, based upon the previous year’s productivity and piece rate, the employer’s average worker would not otherwise earn the new AEWR.
When workers challenged this interpretation, Judge Richey held that the “average worker interpretation” was improper and ordered the Secretary to adopt a “proportional increase interpretatiоn” of the 1978 regulation. Under that interpretation, whenever the Secretary increases the AEWR all employers must increase their piece rates by the same proportion.
NAACP v. Donovan,
The Secretary did not appeal NAACP II, opting instead to pursue the average worker policy by adopting a new rule to that effect. See 48 Fed.Reg. 33684, 33687 (1983) (notice of proposed rule). Until the Secretary issued a valid new rule, however, he was bound by NAACP II to require that growers pay their H-2 workers the piece rate calculated according to the proportional increase interpretation of the 1978 regulation. The growers, fearing that the Secretary would not promulgate a new rule before the start of the approaching 1983 harvest, sought аnd obtained a court order compelling him to issue a new rule by September 1 of that year. Kent Barley, Inc. v. Donovan, No. 83-0079 (W.D.Va. Aug. 18, 1983).
On September 2, the Secretary issued a new rule that codified the average worker interpretation of the 1978 regulation. 48 Fed.Reg. 40168, 40175. Representatives of the workers immediately filed suit to challenge the new regulation, and on September 8 Judge Richey preliminarily enjoined its enforcement. NAACP v. Donovan, No. 82-2315 (D.D.C.1983). Thus, throughout the 1983 harvest (except for the week of September 2-8) the Secretary was under court order to require the growers to pay their H-2 workers the piece rate calculated according to the 1978 regulation. The growers nonetheless paid only the lower piece rate calculated according to the 1983 regulation.
On appeal we vacated Judge Richey’s preliminary injunction prior to the 1984 harvest, but we did not reach the merits of the workers’ challenge to the 1983 regulation.
NAACP v. Donovan,
On July 9, 1985 we did reach the merits of the workers’ challenge, and we set aside the 1983 regulation because the Secretary had not adequately explained his reason for adopting it.
NAACP v. Donovan,
In September 1985 the growers filed the present action challenging the Secretary’s *1268 court-ordered (i.e. proportional increase) interpretation of the 1978 rеgulation. The workers counterclaimed for the difference between what they were paid (under the invalid 1983 regulation) and what they claim they are entitled to (under the 1978 regulation) for the harvests from 1983 through 1985.
The district court noted that the meaning of the 1978 regulation had been fully litigated in
NAACP II
(to which the growers had not been parties) and precluded the growers from relitigating that issue.
Frederick County Fruit Growers Ass’n v. McLaughlin,
When the Supreme Court held in
Martin v. Wilks,
The district court also noted in
FCFGA III
that subsequent events had mooted the growers’ prospective challenge to the Secretary’s interpretation of the 1978 regulation.
Id.
at 21 n. 3. In 1987 the Secretary repealed that regulation, 52 Fed.Reg. 11460, 11466, and promulgated a new piece rate regulation, 52 Fed.Reg. 20496, 20521 (codified at 20 C.F.R. § 655.102(b)(9)(h)), which we upheld in
AFL-CIO v. Dole,
On appeal the growers argue that the district court erred first in awarding the workers backpay for the 1983 and the 1985 harvests and then again in calculating the interest due on those awards. The workers do not cross-appeal the district court’s denial of their backpay claim for the 1984 harvest. For ease of exposition, we begin with the 1985 backpay award.
II. The 1985 Harvest
Recall that the Secretary required each grower to include in its job clearance order for the 1985 harvest a promise to pay its H-2 workers the higher piece rate, calculated according to the district court’s interpretation of the 1978 regulation in
NAACP II.
Each grower’s promise in the job clearance order created a contractual obligation running from that grower to each of its workers. The appropriate remedy for the growers’ breach of that contractual obligation is backpay, and the district court so held.
FCFGA I,
The growers’ lone defense to contract liability for the 1985 harvest is that they promised to pay the higher piece rate only because the Secretary rеquired them to do so, and “[tjhe sole predicate for [the Secretary’s] action was the district court’s injunction ] in NAACP [II].” The growers seem to be arguing that if only the district court had not improperly precluded them from relitigating the issue decided in NAACP II, and they had been able to show that that decision was wrongly decided, then they would be discharged from their promise to pay the higher piece rate.
*1269
Even assuming, however, that
NAACP II
is wrongly decided and that the Secretary was therefore mistaken in requiring the growers to agree to pay the higher piece rate for the 1985 harvest, the fact remains that the growers did promise to do so. The growers do not argue on appeal that their promise was made under duress. Nor do the growers argue that by filing letters of protest with the Secretary they conditioned performance of their promise upon losing a court challenge to
NAACP II
on the merits, or that they otherwise preserved their right to challenge in court the obligation they freely undertook. In short, the growers fail to assert any ground that might excuse nonperformance of their contract; therefore they remain bound by their voluntary and unconditional promise to pay the workers the higher piece rate for 1985.
Cf. Ballay v. Legg Mason Wood Walker, Inc.,
III. The 1983 Harvest
The district court awarded backpay to the workers for the 1983 harvest based not upon contract law but upon the principle of equitable restitution. According to the district court, the workers are entitled to restitution because the 1983 regulation, which permitted the growers to pay the lower piece rate, was subsequently held invalid in
NAACP IV;
as a result, the growers paid the workers less than they were obliged by law to pay, i.e., under the 1978 regulation as interpreted in
NAACP II. FCFGA I,
A. Issue Preclusion
The growers claim that under the teaching of the Supreme Court in Martin v. Wilks, they are entitled to relitigate the issue decided in NAACP II. Several years before the plaintiffs in that case filed suit, the NAACP and individual blacks had sued the city of Birmingham, Alabama, alleging that the fire department discriminated on the basis of race in its hiring and promotion practices. The parties to that earlier case had entered into a settlement agreement that provided, among other things, that the fire department would prefer minority applicants for employment and minority candidates for promotion. The district court then entered a consent decree embodying the settlement. Soon thereafter a group of white fire fighters (the plaintiffs in Martin v. Wilks) sued the city, alleging that it was discriminating against them by making promotion decisions on the basis of race. The city admitted that its promotion decisions were not color-blind but defended its practice on the ground that it was merely complying with the consent decree entered in the previous case. The city also argued that because the white fire fighters had been aware of the previous action and had chosen not to intervene, they should not be allowed to challenge the consent decree after the fact.
The Supreme Court disagreed. Invoking the “deep-rooted historic tradition that everyone should have his own day in court,”
The district court nevertheless held that the growers are not entitled to relitigate the issue decided in
NAACP II.
As a threshold matter, the district court stated that even if the growers were successful in such a challenge,'they would still be liable for backpay: According to the court, the backpay award was “made independently of the collateral estoppel effect of the previous
NAACP
litigation, and the
Martin
decision simply does not undermine, or even implicate, these- back-wage rulings.”
FCFGA III,
Alternatively, the district court distinguished
Martin v. Wilks
on two grounds: First,
“Martin
involved a collatеral attack on a consent decree whereas here the Growers are trying to overturn a final court order granting declaratory and in-junctive relief despite [the Secretary’s] vigorous litigation efforts.”
Id.
at 20 (emphasis omitted). That the previous case had been concluded by a consent decree, however, was in no way significant to the Court’s reasoning in
Martin v. Wilks. See
In defense of the result, if not the reasoning, of the district court, the workers point out that in a footnote the Supreme Court recognized an exception to the rule in
Martin v. Wilks:
a non-party may be bound by a judgment “when, in certain limited circumstances, a person, although not a party, has his interests adequately represented by someone with the same interests who is a party.”
In
NAACP II
the Secretary did initially defend the interpretation of the 1978 regulation that the growers now seek an opportunity to-advance for themselves. After he lost in the district court, however, the Secretary decided not to appeal; rather, in order to pursue his interest in regulating future conduct, he decided to issue a new rule. The growers were concerned in part about the minimum wage rate that would apply in the interim - before a new rule could become final; thus, the growers had an interest in pursuing an appeal that the Secretary did not in the end “adequately represent.”
Cf. United Airlines v. McDonald,
The rule in
Martin v. Wilks
does not necessarily entitle the growers to relitigate the issue decided in
NAACP II,
however. As the growers recognize, the principle behind
Martin v. Wilks
is not that any person may attack a final judgment with which he or she simply disagreеs. Nor does that case state that a non-party may never be adversely affected by a judgment. Rather,
Martin v. Wilks
stands for a more modest proposition: One may challenge a judgment rendered in one’s absence if (and only if) it affects one’s legal right — in that case the right to be considered for promotion free of racial discrimination.
See Martin v. Wilks,
Therefore, in order to relitigate the meaning of the 1978 regulation, the growers must show that the Secretary, by changing her interpretation of the 1978 regulation in compliance with the judgment in NAACP II, infringed upon their legal right. The growers assert three “interests” that they claim were harmed by the decision in NAACP II
First, the growers point to the financial harm they suffered because the court required that the Secretary order the growers to pay higher wages to their H-2 workers. It does not follow, however, that any legal right of the growers was affected. If the Secretary had changed her interpretation of the 1978 regulation on her own, then the resulting financial harm to the growers would not by itself entitle them to judicial relief; they would have to show also that there was a procedural or substantive (i.e., a legal) defect in the Secretary’s changed position. No less is required just because the Secretary acted pursuant to a court order.
Second, the growers argue that NAACP II was decided upon the basis of incorrect factual information, and that the court would have been apprised of the true facts if the growers had been parties — or by extension, if they are now allowed to reliti-gate the issue. Assuming that to be true, however, it would still not establish any harm to a legal right of the growers. One has no legal right to the correct resolution of a dispute between strangers.
Third, the growers cite
United States v. South Florida Water Management Dist.,
Finally, we note that the growers do not argue on appeal that the Secretary's (court-ordered) interpretation of the 1978 regulation is arbitrary and capricious. Therefore, we express no opinion about any possible tension between
Martin v. Wilks,
which might require that the growers be given an opportunity to establish that the Secretary is denying them their legal right to an interpretation of the 1978 regulation that is not arbitrary and capricious, and
GTE Sylvania v. Consumers Union,
We conclude that Martin v. Wilks governs this case, but the growers have not established that the district court order in NAACP II infringes upon any legal right of theirs. As a result, the growers are not entitled to relitigáte the issue resolved in that case. We turn next to the growers’ alternative arguments that the district court erred in awarding restitution to the workers for the 1983 harvest.
B. Restitution
The district court analyzed the remedial aspect of this case much as it would a successful court challenge to a rate increase that had been duly implemented by a regulated carrier after approval by a regulatory agency. “[E]quitable restitution" is the proper remedy, the district court said, “when funds have been either paid or withheld pursuant to an invalid administrative edict.”
FCFGA I,
In fashioning a remedy based upon equitable restitution, “the trial court is vested with broad discretionary power; appellate review is correspondingly narrow.”
Thompson v. Washington,
First. The growers argue that “[t]he purpose of restitution is to restore a person ‘to the position he formerly occupied either by the return of something he previously had or the receipt of its equivalent in money,’ ” quoting Restatement of Restitution § 1, comm, a (1937). Viewed in this light, the workers are not entitled to restitution because they “never possessed the disputed wages.”
Restitution is not so limited a remedy, however. Courts regularly award as restitution reasonable compensation for services rendered.
See
Dan B. Dobbs,
The Law of Remedies
§ 4.4, at 259 (1973);
see also
Restatement § 1, comm. b (noting that “a physician [who] attends an insensible person” may be entitled to “restitution”); Dobbs § 4.1, at 222 (restitution not limited to “restoration ... of property or money taken from the plaintiff”). Indeed, this court has previously awarded restitution when an employer failed to pay the lawful minimum wage.
Mitchell v. Riegel Textile, Inc.,
Second.
The growers assert that the workers are not entitled to restitution be
*1273
cause restitution is generally not available to one who “voluntarily” confers a benefit upon another, Restatement § 112; Dobbs § 4.9, and the workers’ employment was of course voluntary. In the context of restitution, however, it seems that voluntariness is a somewhat specialized concept; a court will deny restitution for a voluntary transaction only if the claimant confers the disputed benefit “with an intention to make a gift” or “without affording [the recipient] the opportunity to reject the benefit.”
Id.
§ 4.9, at 299;
see also
Restatement § 2; 2 Palmer § 10.1, at 359. Here the workers obviously did not perform their labor at a reduced rate because they intended to confer a gift upon the growers — who are not so brazen as to claim otherwise — and the growers had ample opportunity to reject the fruits of the workers’ labor. Thus, although they entered the employment relation with the growers voluntarily, the workers are not disqualified on that basis from receiving restitution.
See DCC,
Third.
The growers claim that “it is doubtful that a claim for restitution can rest solely on the invalidation of a regulation” on a procedural, as opposed to a substantive, ground. We find no basis for the growers’ doubt. In both
DCC
and
Williams
we invalidated on procedural grounds fare increases approved by the Metropolitan Transit Commission and we ordered the carrier to make restitution to the riders.
See DCC,
Fourth.
The growers argue that the workers should be denied restitution as a matter of equity: The growers claim that in underpaying their workers, they reasonably relied upon the 1983 regulation, and ordering restitution would “inflict substantial hardship” upon them.
See, e.g., Moss v. Civil Aeronautics Bd.,
In the summer of 1983, when the growers made plans for the 1983 harvest and filed their job clearance orders to hire H-2 workers, there was at the least a significant possibility that the 1983 harvest would be governed by the 1978 regulation. On July 22 the Secretary issued a proposed “average worker” rule of the sort favored by the growers. 48 Fed.Reg. 33684, 33687. It was not until August 18, however, that the growers secured a court order requiring the Secretary to issue a new regulation by September 1, 1983, and that order specifically provided that it should not “be construed as ... in any way limiting the right of [the Secretary] to publish a final interpretive piece rate adjustment rule in accordance with [the Secretary’s] own policies,”
Kent Barley, Inc.,
slip op. at 2. Therefore, while the Secretary might have been more likely to adopt something like the rule he had proposed in July 1983 than something completely different, prior to September 2 the growers could not have reasonably relied upon the Secretary’s adopting any particular regulation in his final rule decision. And by September 2, when the Secretary issued the rule upon which the growers now claim to have relied, the growers’ plans for the harvest— including their decisions regarding how many workers to hire — were already complete; it was too late for the growers to change them in reliance upon the new regulation. Indeed, in some areas the harvest had already begun. C
f. FCFGA I,
Moreover, by September 8, when the district court enjoined the Secretary from implementing the 1983 regulation, the growers knew “full well that the [1983 regulation] was, if not flatly invalid, of at least dubious validity.”
FCFGA I,
Fifth.
The growers argue that although the district court has broad discretion to award restitution, it “abused its discretion by relying on [an] erroneous factor[ ].” The growers here point to the district court’s statement that they underpaid their workers “in direct violation of this Court’s Order of September 8, 1983.”
FCFGA I,
If the district court had really based its restitution order to any meaningful extent upon the ground that the growers had violated the September 8 order, then a remand might be necessary.
See In re Subpoena Served Upon the Comptroller of the Currency,
Sixth. The growers argue that even if restitution is an appropriate remedy, the district court abused its discretion by failing “to consider whether it should direct restitution in an amount less than the difference between” the amount due under the 1978 regulation and the amount actually paid. In Williams we stated the following general rule:
Ordinarily ... the proper disposition on setting aside a rate increase unlawfully ordered by the Commission [is] to compel the regulated company to restore the entire difference between the higher fares collected under the invalid order and the amount that it would have received from the fare schedule previously in effect.
C. Conclusion
The growers raise additional challenges to the district court’s award of restitution, but they are either reformulations of the arguments discussed above or otherwise lack merit. We therefore reject the growers’ challenges and affirm the аward of full restitution to the workers for the 1983 harvest.
IV. Prejudgment Interest
There is no doubt that the district court may award prejudgment interest on funds that are to be paid over as restitution.
Bebchick v. Washington Metropolitan Transit Comm’n,
1983.
In determining when interest begins to accrue, one factor for the district court to consider is the date upon which “the amount to be restored became relatively certain.”
Bebchick III,
The growers rely heavily upon
Bebchick III.
In that case we ordered a regulated bus company to place into a “riders’ fund” excess fares that it had collected pursuant to an invalid order of the Metropolitan Transit Commission, together with interest. We held that the interest should accrue, however, not from the date that the fares were wrongfully collected but from the date of our earlier decision,
Bebchick v. Washington Metropolitan Transit Comm’n,
The growеrs argue that, like the liability of the carrier in
Bebchick,
their liability became “relatively certain” only after a court first ordered restitution. In the
Bebchick
litigation, however, the defendant had no reason to believe before that court decision that it had wrongfully retained fares collected in excess of the lawful rate. Here, in contrast, the district court found that the growers had known they were underpaying their workers even as they did so.
FCFGA II, 709
F.Supp. at 247. Based upon that finding, we perceive no error in providing that interest accrue as of the date that the workers were underpaid.
See Mitchell,
1985.
Soon after the 1985 harvest, the district court for the Westеrn District of Virginia ordered the growers to place the disputed funds into an interest-bearing account with the Department of Labor as trustee.
Frederick County Fruit Growers Ass’n v. Brock,
No. 85-0142-D, slip op. at 2-3 (W.D.Va. Dec. 17, 1985). In
FCFGA II,
the district court here held that the workers were entitled to “whatever rate of interest the ... funds have earned ..., so long as the net result ... is ... a rate not less than 9%.”
The growers argue that the district court’s imposition of the 9% minimum rate of return was improper. Payment into an interest bearing account, they say, “stops the running of prejudgment interest.” The growers’ sole support for this assertion is that the payment of money into the court under Fed.R.Civ.P. 67 for deposit in an interest bearing account tolls the defendants’ liability for prejudgment interest. See 12 Wright & Miller § 2991, at 51. The growers argue that “[tjhere is no reаson to *1276 treat the funds in this case any differently,” but they are wrong.
When funds are deposited with the court, the court undertakes to ensure an adequate rate of return. Here, in contrast, the growers unilaterally placed the funds into an interest-bearing account; if the growers were doubtful about recovering the disputed funds, they had little incentive to secure an adequate rate of return. Presumably in order to protect the workers from the possibility of such desultory decision-making, the district court set a minimum interest rate. We see no error in its doing so.
V. Conolusion
The growers are not entitled to challenge the decision in NAACP II, and they have established no legal error in the district court’s award of backpay to the workers for the 1983 and 1985, harvests. The judgment of the district court is therefore in all respects.
Affirmed.
