delivered the opinion of the Court.
The federal question which survives proceedings in the Florida state courts is whether renewal notes representing the purchase price of goods sold and delivered are uncollectible if it is found that the vendor violated the Robinson-Patman Act, 49 Stat. 1526, 1528; 15 U. S. C. §§ 13, 13a.
Bruce is a canner and, over a period of years, bought its cans chiefly from The American Can Company. A debt accumulated which was put into promissory notes and on one or more occasions they were renewed, reduced by amounts which had been paid. Upon eventual default, two suits, later consolidated, were brought on renewal notes aggregating about $114,000. As to each note, Bruce pleaded in defense that “the consideration for said notes is illegal and said notes void and of no force and effect.” This was said to be for the reason that the Can Company had sold to others at prices which discriminated against Bruce and thereby violated the Robinson-Patman Act.
The alleged discrimination chiefly relied upon consisted of quantity discounts. Annual purchases by Bruce *745were about $350,000. Some other canners bought much larger quantities. The Can Company’s contract with all its customers allowed a discount of 1% on annual purchases of $500,000, and nothing to those whose purchases were less than that. It was so graduated as to give a maximum discount of 5% to a customer whose purchases were $7,000,000 a year. The consequence is that relatively small packers pay 5% more for their cans than their largest competitors.
It is claimed that this advantage to quantity buyers renders the quantity discount per se a violation of the Robinson-Patman Act. To sustain the defense in this case it would be necessary to so hold. It is not denied that Bruce got the same discounts as other purchasers of like quantities when it qualified, and in one year Bruce was in the $500,000 bracket and received the 1 % discount. It is not claimed that the Can Company failed to give discounts where earned under this uniform contract, or that discounts were given where not so earned. Bruce received the same discounts as others within its classification and it is not questioned that had it been a purchaser of larger quantities it would have been allowed the same discount as other purchasers of that class.
Before a court could sustain the defense in this particular case, it would also have to overcome other difficulties of law and fact. The Act does not prohibit all quantity discounts but expressly permits them under certain conditions. It indicates, too, that the Federal Trade Commission is the appropriate tribunal to hear in the first instance the complicated issues growing out of grievances against a quantity discount practice of a seller. 49 Stat. 1526; 15 U. S. C. § 13 (a). Quantity discounts are among the oldest, most widely employed and best known of discount practices. They are common in retail trade, wholesale trade, and manufacturer-jobber relations. They are common in regulated as well as unregulated *746price structures. Congress refused to declare flatly that they are illegal. They become illegal only under certain conditions and when they are illegal it is as much a violation to accept or receive as to allow them. Bruce, in one of the years included in its balance of account, purchased more than a half million dollars of cans on which it received precisely the kind and amount of discount it now asserts to be illegal.
The argument is made that such a remedy as Bruce seeks here would support the anti-monopoly policy of Congress. But Bruce is not complaining of the high price of cans. Bruce complains of a lower price for cans to others—which would enable competitors to put their products on the market cheaper. This may well put Bruce to some disadvantage, but it does not follow that Congress would forbid the savings of large-scale mass production to be passed along to consumers. The economic effects on competition of such discounts are for the Trade Commission to judge. Until the Commission has determined the question, courts are not given guidance as to what the public interest does require concerning the harm or benefit of these quantity discounts on the ultimate public interests sought to be protected in the Act. It would be a far-reaching decision to outlaw all quantity discounts. Courts should not rush in where Congress feared to tread.
Because of a more fundamental defect in petitioner’s case, however, the Court does not find it necessary to consider the effect of these features of the Act on this case, as would be necessary before a conclusion could be reached that petitioner should win on the merits. On the questions of fact, considerable evidence was taken at pre-trial hearings and the parties are in dispute as to whether the decision thereon was a final judgment and, if so, as to whether the defense was not also adjudicated to be insufficient on the facts. Although the record is unsatisfactory, *747we take it that all of the sales evidenced by the notes were made after the passing of the Robinson-Patman Act. It appears, however, that the notes are not identified with any particular sale but represent a balance remaining on a running account of sales and credits in many of which a claim of discrimination might not be supportable. The indebtedness they supplant is conceded to have been incurred before February, 1940. The purchases covered at least a four-year period and involved two types of cans. The purchase price which Bruce asks us to excuse it from paying is not identified either as to type of can or date of transaction. But petitioner contends that it is not necessary in proving a discrimination to show that others received a different discount on the same type of can at approximately the same time “because the scheme of discount by aggregate dollar volume of annual sales comprehends all cans bought whatever their size or price.” To sustain this position would mean that a sale to a competitor of large cans in 1940 at a higher discount invalidated a sale of small cans to petitioner in 1936 so that petitioner need not pay the contract price for cans delivered that year. The contention is simply that if some purchasers got larger discounts on any bill for cans than petitioner got, the bill against petitioner and notes in settlement and extension of it are uncollectible.
However, for the purposes of this decision, in view of the uncertain nature of the proceedings below, we assume, but do not decide, that the defense on the facts has been or could be established as pleaded. We do not decide whether the quantity discount plan, whatever the facts were, violated the Robinson-Patman Act. The sole question we decide is whether notes given for purchases are unenforceable if the quantity discount plan violates the Act. Petitioner suggests that the Court may take two paths to the answer, but that the answer will be yes. The *748broad ground petitioner offers is “that a transaction unlawful under the Robinson-Patman Act constitutes criminal conduct upon which no money judgment can be based.” Petitioner also offers a narrow ground on which we can yet decide in its favor. “But, if it be admitted that the buyer [sic] is entitled to the fair value of the goods,” petitioner says, respondent probably already has been paid the fair value of all the cans bought in 1936-40. When that value has been determined by the trial court, it urges, it will be found that the amount in notes is substantially equivalent to the amount of discrimination in discount.1
In effect, petitioner is treating the $114,000 in notes as representing the discount it claims it should have gotten on its 1937-42 purchases of $2,000,000. This alternative argument is that petitioner is liable only for the fair value of all the cans it bought, and in this suit it asks the courts to determine what that fair value was. But the fact is that as to the transactions for which petitioner paid $2,000,000 it has already paid the agreed price. Those transactions cannot be identified with particularity, but they were paid for at respondent’s prices. Petitioner did not allege and does not contend that the notes represent specific transactions or that the sales for which they were given could be identified. Mr. Bruce conceded in his testimony that the notes simply represent a balance of an account which mingled the prices of individual transactions.*7492 In its brief here, petitioner’s only response to respondent’s statement that “None of the original notes . . . had been tied to a particular transaction” is that “The record shows that all of'the notes are tied to the entire series of transactions.” There may be substantial equivalence numerically in the amount of the notes and the amount of alleged discrimination, but it cannot be said that the notes represent the separate item of price discrimination.3
*750The Act prescribes sanctions, and it does not make uncollectibility of the purchase price one of them. Violation of the Act is made criminal and upon conviction a violator may be fined or imprisoned. 49 Stat. 1528, 15 U. S. C. § 13a. Any person who is injured in his business or property by reason of anything forbidden therein may sue and recover threefold the damages by him sustained and the costs of suit, including a reasonable attorney’s fee. 38 Stat. 731, 15 U. S. C. § 15. This triple damage provision to redress private injury and the criminal proceedings to vindicate the public interest are the only sanctions provided by Congress.
It is contended that we should act judicially to add a sanction not provided by Congress by declaring the purchase price of goods uncollectible where the vendor has violated the Act. It may be admitted as argued that such a sanction would be an effective enforcement provision. Addressed to Congress, this argument might be persuasive, but the very fact that it would obviously be an effective sanction makes it even more significant that *751the Act made no provision for it; that no committee dealing with the Robinson-Patman Act proposed it; that not one word suggesting its consideration appears in the debates of Congress; no proponent of the Act pointed out in its favor that it would be self-enforcing because of this sanction; and no opponent pointed with alarm to the consequences of such a drastic sanction on the commerce of the nation. On the contrary, a proposed provision of the Act, passed only by the Senate which later receded, shows that Congress gave consideration to no sanction more extreme than to compel the remission of the excess charged. See S. 3154, § 2 (d), 74th Cong., 1st Sess., S. Rep. No. 1502, 74th Cong., 2d Sess., p. 8: Conference Rep., H. Rep. No. 2951, 74th Cong., 2d Sess., p. 8. Congress declined to adopt this relatively moderate provision and at no time does it appear that either house of Congress wanted to go so far as to permit a buyer to get goods for nothing.
Where the interests of individuals or private groups or those who bear a special relation to the prohibition of a statute are identical with the public interest in having a statute enforced, it is not uncommon to permit them to invoke sanctions. This stimulates one set of private interest to combat transgressions by another without resort to governmental enforcement agencies. Such remedies have the advantage of putting back of such statutes a strong and reliable motive for enforcement, which relieves the Government of cost of enforcement. Such private remedies lose, of course, whatever advantage there may be in the presumed disinterested, public interest standards and expertness of a governmental agency which has the initiative control of retributory measures. It is clear Congress intended to use private self-interest as a means of enforcement and to arm injured persons with private means to retribution when it gave to any injured *752party a private cause of action in which his damages are to be made good threefold, with costs of suit and reasonable attorney’s fee.
Bruce, it appears, already has undertaken the triple damage suit remedy against the Can Company. Bruce’s Juices, Inc. v. American Can Co., No. 569, Civ. T., S. D. Fla., 1942. To indicate its need that the Court establish this additional remedy unauthorized by Congress, it seeks to discredit and belittle both of the remedies Congress has expressly authorized. It says, “The triple damage suit is likely to prove protracted and expensive; damages caused by a disadvantageous competitive position are so speculative as to be usually unprovable. Nor can the buyer rely for protection upon the action of the government. The Department of Justice or the Federal Trade Commission may never get around to the matter.” It is a little dubious whether the sort of remedy which has been in litigation over four years in this case which Bruce asks us to reverse and send back again, is an antidote for “protracted and expensive” triple damage suits. Moreover, if Bruce can in this suit prove that the prices respondent charged were illegal, as it must in order to win, it can do the same in a triple damage suit. The damages sustained because of discrimination are no more “speculative” nor “unprovable” in one suit than in the other, and their establishment in the statutory form of action carries a bonus.
Annexation of the proposed defense to the statute by implication either as an inference of unexpressed intention of Congress or as the result of some doctrine of common law, would be justified only if it would be at least a rational, nondiscriminatory and appropriate means of making the policy of the statute effective. To allow a buyer to get his goods for nothing because the seller violated the Act by giving someone else a greater discount, does not meet this test.
*753It would seem that one test of the rationality and appropriateness of such a defense because of a violation of the Act would be that the reparation it permits should be measured at least roughly by the extent of the injury caused by the violation. This, of course, is the principle of the suit for triple damages. But that is not the principle of the defense here urged. The extent of its indemnity is not measured by injury, and not measured by the dealings affected with the alleged violation. It is measured solely by the amount of credit the buyer obtained from the seller. The seller would lose the amount carried in notes or in open account. Had Bruce’s delinquency been greater, so would its gain; had there been no credit asked or given the buyer could have had no remedy by way of defense. The obvious consequence would be to discourage vendors from extending credit where the operation of this rather difficult statute is in doubt. Since the danger of loss under the proposed remedy is greatest in the case of small buyers who get small discounts, the consequence would be to deny the small buyers credit and trust only those who, having the largest discounts, would be least likely to defend on a claim of violation. This result would hardly comport with the argument, so much dwelt upon by petitioner, that its status is that of a small business concern trying to battle a business giant. But we cannot suppose that “little fellows” are always buyers and only giants sell goods. Bruce itself is a seller of canned goods and if its trade practices include quantity discounts, this “little” canner might be on the other side of the same issue trying to collect against a small wholesaler who had less discount than a larger one. To decide issues of law on the size of the person who gets advantage or claims disadvantage is treacherous.
This construction which would make a grant of credit a point of vulnerability could be avoided only by holding that the whole purchase price, not merely that involved *754in the credit, is uncollectible and recoverable even if voluntarily paid. In that case, the volume of the transaction, rather than the volume of the credit extended, would measure the loss a seller might suffer from violating the Act.
But, of course, if the discount system of the Can Company makes all of the Bruce purchases illegal and the price thereof recoverable, all sales to others under the discount system must be similarly tainted. It is hard to see how any of the Can Company’s sales are valid if these to Bruce are void on the theory advanced. If this view is taken, certainly the remedy would soon end illegal quantity business discounts—by ending the business. We do not believe Congress has contemplated so deadly a remedy or has left the way open to us by judicial edict to dislocate business as such a holding would do. It must not be forgotten that such a decision would have retroactive effect for several years and unsettle many accounts. We cannot justify a judicial declaration to this effect.
But if only a few cases are to be unsettled—those, say, in positions similar to Bruce’s—what becomes of the policy of nondiscrimination? Other canners who have paid cash find themselves competing with Bruce who is absolved from paying for a very large part of its cans—something like one-third of its annual dollar volume being involved in this case. In other words, as penalty for establishing a uniform one to five percent discount, the Can Company would be obliged to give Bruce something over a 30% discount on one year, or about 5% on all purchases shown by the evidence ever to have been made.
It is urged that holdings under the Sherman Antitrust Act supply an analogy for allowing this defense under the Robinson-Patman Act. The former provides, among other things, that every contract in restraint of trade or commerce “is hereby declared to be illegal.” 26 Stat. 209, *75550 Stat. 693, 15 U. S. C. § 1. This Court has held that where a suit is based upon an agreement to which both defendant and plaintiff are parties, and which has as its object and effect accomplishment of illegal ends which would be consummated by the judgment sought, the Court will entertain the defense that the contract in suit is illegal under the express provision of that statute. Continental Wall Paper Co. v. Louis Voight and Sons Co., 212 U. S. 227. Cf. Sola Electric Co. v. Jefferson Electric Co., 317 U. S. 173. But when the contract sued upon is not intrinsically illegal, the Court has refused to allow property to be obtained under a contract of sale without enforcing the duty to pay for it because of violations of the Sherman Act not inhering in the particular contract in suit and has reaffirmed the “doctrine that 'where a statute creates a new offense and denounces the penalty, or gives a new right and declares the remedy, the punishment or the remedy can be only that which the statute prescribes.’ ” D. R. Wilder Mfg. Co. v. Corn Products Refining Co., 236 U. S. 165, 174-175; Connolly v. Union Sewer Pipe Co., 184 U. S. 540.
Moreover, no single sale can violate the Robinson-Pat-man Act. At least two transactions must take place in order to constitute a discrimination. Thus, a contract may be made today which has no legal defect under the Robinson-Patman Act. A week later, another sale may be made at a different price or at a different discount, and the latter taken into consideration with the former may establish a discrimination. Whether a sale would be rendered void only because of simultaneous discrimination or preexisting ones, or whether a contract valid when made becomes void by reason of later transactions, and, if so, how much later, are questions we need not decide now. It is plain that the violation, if there was one, is not inherent in the contract sued upon, whether it be the notes or the sale of the goods, but can only be found in different trans*756actions which a party to the litigation had with third persons who are not parties. No such defense has been approved under the Sherman Act, and, furthermore, these characteristics show that the entire basis for judging under the two Acts is different and that the case law as to the Sherman Act does not fit the Robinson-Patman Act.
None the less, we are urged to supply judicially the sanction of invalidating obligations to pay for goods sold and delivered because, it is said, otherwise the courts become parties to the enforcement of a discrimination. If, in order to prove his own case, a plaintiff proves his violation of law, then no court will aid the plaintiff to recover.4 Here, however, what the plaintiff must show is the notes which import consideration. If consideration is denied, he can prove that cans were sold and delivered at a stated price. That is no violation of law. It is only when the Court goes outside of the dealings between plaintiff and defendant and it is proved that the same kind of cans were sold to others at different prices within a relevant period of time, amounting to a discrimination—a fact unnecessary to sustain the plaintiff’s cause of action— that the basis of the defense asserted here appears. The Court does not give its approval to transactions between one of the litigants and a third party just because it holds them irrelevant in this litigation.
The defendant’s claim to be freed of the obligation to pay his promissory note because the payee, as vendor of cans, made sales to others that when compared with sales *757to itself may be held unlawfully discriminatory, cannot be supported as resting on any congressional word or policy. Not only was this remedy not named by Congress, but it would be surprising if it had been, in view of the remedies Congress did give. We have assumed for the purposes of this case that petitioner could establish that the prices respondent charged were discriminatory so that they violated the Act. But if petitioner can show that, clearly it would be entitled to recover in a triple damage suit supported by the same evidence. For despite petitioner’s plaint on the difficulty of proving damages, it would establish its right to recover three times the discriminatory difference without proving more than the illegality of the prices. If the prices are illegally discriminatory, petitioner has been damaged, in the absence of extraordinary circumstances, at least in the amount of that discrimination. No reason suggests itself why Congress should have intended a remedy by which the victim of discrimination could recover by defense only one-third of what he could recover, on the same proof, by offense. The inducement of thrice the damages suffered may bring the sufferer to aid in enforcement of the statute. To assure his help, however, it would hardly be thought appropriate to offer him the choice of taking only one-third that amount. Since the remedy embodied in petitioner’s second theory would be but a weak one-third shadow of the one Congress expressly gave, we cannot see the need for judicial reduplication in miniature. We hold that federal law does not support the defense alleged and the judgment of the Florida Supreme Court is
Affirmed.
On petitioner’s first theory, clearly no recovery on quantum meruit could be had. The general rule is that a transaction wholly illegal will not support such a suit. See Williston, Contracts (Rev. ed., 1938) § 1786A; Restatement, Contracts, § 598, Comment c. And on Bruce’s second theory, because of the leniency with which respondent extended credit, it would be impossible for respondent to show which cans the notes represent and it would of course be unable to establish their fair value. If we hold the notes uncollectible, therefore, respondent could not recover on quantum meruit, and Bruce would get a windfall.
His testimony on this point follows:
“Q. Mr. Bruce, do the notes evidence the purchase price of any particular size of cans you purchased from the American Can Co.?
A. There is nothing on the face of the notes that shows what size they were.
Q. During that period you purchased a certain size can?
A. It was purchased during a certain period.
Q. Did you run a separate account on the grocery can and on the soft drink can, or small and large?
A. No sir.
Q. The notes themselves simply represent that account, irrespective of the size of the cans?
A. Yes sir, the blanket way.
Q. In a blanket way. In other words there was no distinction made in your account between the large and small cans, I mean in the indebtedness?
A. Not while the notes were accruing.
Q. In other words the notes in question are for the purchase price of both large and small cans?
A. That is right.”
If the notes are considered alternatively as representing respondent’s price due on the latest purchases to that amount in late 1939 and early 1940, petitioner, on its theory, would be entitled to be excused payment of only about 5% of the $114,000, because it is defending on the ground that it ought not to pay the allegedly discriminatory part of the price. But even for this limited purpose, it cannot be established what cans the $114,000 represents, so the court could not determine their fair value.
In Penn-Alien Cement Co. v. Phillips & Southerland, 182 N. C. 437, 109 S. E. 257, the specific sales were identified and the price unpaid. *750The court there held only that the buyer should be excused payment of the discriminatory part of the contract price. But the opinion was given after the court had decided that the appeal was prematurely taken.
The defendant had counterclaimed for treble damages, computed on the basis of the alleged overcharge. The plaintiff urged that treble damages could not be recovered in an action for the purchase price but that the defendant must pay first, and then sue on that claim. The court said simply, “This matter also has not been passed upon by the court below, and there is nothing for us to consider.” 182 N. C. at 441, 109 S. E. at 259. But if the court was right in holding that plaintiff could not recover the overcharge, it would necessarily follow that the counterclaim should have been dismissed. For without paying the overcharge, the defendant would have had no basis on which to rest its claim that it had been damaged in that amount and therefore entitled to treble compensation.
In McMullen v. Hoffman, 174 U. S. 639, for example, the Court refused to enforce a partnership contract which was based on an illegal and fraudulent agreement to submit collusive bids for public construction. The plaintiff argued that the partnership contract itself did not disclose any illegality, but even that was questionable. The Court, moreover, held that the agreement to be partners could not be separated from the general collusive agreement which gave rise to it Agreements with third persons, not parties to the suit, however, were not relied upon by Court or litigants.