delivered the opinion of the Court.

The “filed rate doctrine” prohibits a federally regulated seller of natural gas from charging rates higher than those filed with the Federal Energy Regulatory Commission pursuant to the Natural Gas Act, 52 Stat. 821, as amended, 15 U. S. C. § 717 et seq. (1976 ed. and Supp. III). The question before us is whether that doctrine forbids a state court to calculate damages in a breach-of-contract action based on an assumption that had a higher rate been filed, the Commission would have approved it.

I

Respondents are producers of natural gas, and petitioner Arkansas Louisiana Gas Co. (Arkla) is a customer who buys their gas. In 1952, respondents1 and Arkla entered into a contract under which respondents agreed to sell Arkla natural gas from the Sligo Gas Field in Louisiana. The contract contained a fixed price schedule and a “favored nations clause.” The favored nations clause provided that if Arkla purchased Sligo Field natural gas from another party at a rate higher than the one it was paying respondents, then respondents would be entitled to a higher price for their sales to Arkla.2 *574In 1954, respondents filed with the Federal Power Commission (now the Federal Energy Regulatory Commission)3 the contract and their rates and obtained from the Commission a certificate authorizing the sale of gas at the rates specified in the contract.

In September 1961, Arkla purchased certain leases in the Sligo Field from the United States and began producing gas on its leasehold. In 1974, respondents filed this state-court action contending that Arkla’s lease payments to the United States had triggered the favored nations clause. Because Arkla had not increased its payments to respondents as required by the clause, respondents sought as damages an amount equal to the difference between the price they actually were paid in the intervening years and the price they would have been paid had the favored nations clause gone into effect.

In its answer, Arkla denied that its lease payments were purchases of gas within the meaning of the favored nations clause. Arkla subsequently amended its answer to allege in addition that the Commission had primary jurisdiction over the issues in contention. Arkla also sought a Commission ruling that its lease payments had not triggered the favored nations clause. The Commission did not act immediately, and the case proceeded to trial. The state trial court found that Arkla’s payments had triggered the favored nations clause, but nonetheless held that the filed rate doctrine pre-*575eluded an award of damages for the period prior to 1972. The intermediate appellate court affirmed, 359 So. 2d 255 (1978), and both parties sought leave to appeal. The Supreme Court of Louisiana denied Arkla’s petition for appeal, 362 So. 2d 1120 (1978), and Arkla sought certiorari in this Court on the question whether the interpretation of the favored nations clause should have been referred to the Commission. We denied the petition. 444 U. S. 878 (1979).

While Arkla’s petition for certiorari was pending, the Supreme Court of Louisiana granted respondents’ petition for review and reversed the intermediate court on the measure of damages. 368 So. 2d 984 (1979). The court held that respondents were entitled to damages for the period between 1961 and 1972 notwithstanding the filed rate doctrine. The court reasoned that Arkla’s failure to inform respondents of the lease payments to the United States had prevented respondents from filing rate increases with the Commission, and that had respondents filed rate increases with the Commission, the rate increases would have been approved. Id., at 991. After the decision by the Supreme Court of Louisiana, the Commission in May 1979 finally declined to exercise primary jurisdiction over the case, holding that the interpretation of the favored nations clause raised no matters on which the Commission had particular expertise. Arkansas Louisiana Gas Co. v. Hall, 7 FERC ¶ 61,175, p. 61,321.4 The Commis*576sion did, however, state: “It is our opinion that the Louisiana Supreme Court's award of damages for the 1961-1972 period violates the filed rate doctrine.” Id., at 61,325, n. 18.5 Under that doctrine, no regulated seller is legally entitled to collect a rate in excess of the one filed with the Commission for a particular period. See infra, at 576-579. We granted Arkla's subsequent petition for certiorari challenging the judgment of the Louisiana Supreme Court. 449 U. S. 1109 (1981).6

II

Sections 4 (c) and 4 (d) of the Natural Gas Act, 52 Stat. 822-823, 15 U. S. C. §§ 717c (c) and 717c (d), require sellers of *577natural gas in interstate commerce to file their rates with the Commission. Under § 4 (a) of the Act, 52 Stat. 822, 15 U. S. C. § 717c (a), the rates that a regulated gas company-files with the Commission for sale and transportation of natural gas are lawful only if they are “just and reasonable.” No court may substitute its own judgment on reasonableness for the judgment of the Commission. The authority to decide whether the rates are reasonable is vested by § 4 of the Act solely in the Commission, see FPC v. Hope Natural Gas Co., 320 U. S. 591, 611 (1944), and “the right to a reasonable rate is the right to the rate which the Commission files or fixes,” Montana-Dakota Utilities Co. v. Northwestern Public Service Co., 341 U. S. 246, 251 (1951).7 Except when the Commission permits a waiver, no regulated seller of natural gas may collect a rate other than the one filed with the Commission. § 4 (d), 52 Stat. 823, 15 U. S. C. § 717c (d). These straightforward principles underlie the “filed rate doctrine,” which forbids a regulated entity to charge rates for its services other than those properly filed with the appropriate federal regulatory authority. See, e. g., T. I. M. E. Inc. v. United States, 359 U. S. 464, 473 (1959). The filed rate doctrine has its origins in this Court’s cases interpreting the Interstate Commerce Act, see, e. g., Lowden v. Simonds-Shields-Lonsdale Grain Co., 306 U. S. 516, 520-521 (1939); Pennsylvania R. Co. v. International Coal Co., 230 U. S. 184, 196-197 (1913), and has been extended across the spectrum of regulated utilities. “The considerations underlying the doctrine . . . are preservation of the agency’s primary juris*578diction over reasonableness of rates and the need to insure that regulated companies charge only those rates of which the agency has been made cognizant.” City of Cleveland v. FPC, 174 U. S. App. D. C. 1, 10, 525 F. 2d 845, 854 (1976). See City of Piqua v. FERC, 198 U. S. App. D. C. 8, 13, 610 F. 2d 950, 955 (1979).

Not only do the courts lack authority to impose a different rate than the one approved by the Commission, but the Commission itself has no power to alter a rate retroactively.8 When the Commission finds a rate unreasonable, it “shall determine the just and reasonable rate ... to be thereafter observed and in force.” § 5 (a), 52 Stat. 823, 15 U. S. C. § 717d (a) (emphasis added). See, e. g., FPC v. Tennessee Gas Co., 371 U. S. 145, 152-153 (1962); FPC v. Sierra Pacific Power Co., 350 U. S. 348, 353 (1956). This rule bars “the Commission’s retroactive substitution of an unreasonably high or low rate with a just and reasonable rate.” City of Piqua v. FERC, supra, at 12, 610 F. 2d, at 954.

In sum, the Act bars a regulated seller of natural gas from collecting a rate other than the one filed with the Commission and prevents the Commission itself from imposing a rate increase for gas already sold. Petitioner Arkla and the Commission as amicus curiae both argue that these rules taken in tandem are sufficient to dispose of this case. No matter how the ruling of the Louisiana Supreme Court may be characterized, they argue, it amounts to nothing less than the award of a retroactive rate increase based on speculation *579about what the Commission might have done had it been faced with the facts of this case. This, they contend, is precisely what the filed rate doctrine forbids. We agree. It would undermine the congressional scheme of uniform rate regulation to allow a state court to award as damages a rate never filed with the Commission and thus never found to be reasonable within the meaning of the Act. Following that course would permit state courts to grant regulated sellers greater relief than they could obtain from the Commission itself.

In asserting that the filed rate doctrine has no application here, respondents contend first that the state court has done no more than determine the damages they have suffered as a result of Arkla’s breach of the contract.9 No federal interests, they maintain, are affected by the state court’s action. But the Commission itself has found that permitting this damages award could have an “unsettling effect ... on other gas purchase transactions” and would have a “potential for disruption of natural gas markets . . . .” Arkansas Louisiana Gas Co. v. Hall, 13 FERC ¶ 61,100, p. 61,213 (1980).10

*580Even were the Commission not on record in this case, the mere fact that respondents brought this suit under state law would not rescue it, for when Congress has established an exclusive form of regulation, “there can be no divided authority over interstate commerce.” Missouri Pacific R. Co. v. Stroud, 267 U. S. 404, 408 (1925). Congress here has granted exclusive authority over rate regulation to the Commission. In so doing, Congress withheld the authority to grant retroactive rate increases or to permit collection of a rate other than the one on file. It would surely be inconsistent with this congressional purpose to permit a state court to do through a breach-of-contract action what the Commission itself may not do.

We rejected an analogous claim earlier this Term in Chicago & North Western Transp. Co. v. Kalo Brick & Tile Co., 450 U. S. 311 (1981). There, a shipper of goods by rail sought to assert a state common-law tort action for damages stemming from a regulated rail carrier’s decision to cease service on a rail line. We held unanimously that because the Interstate Commerce Commission had, in approving the cessation, ruled on all issues that the shipper sought to raise in the state-court suit, the common-law action was pre-empted. In reaching our conclusion, we explained that “[a] system under which each State could, through its courts, impose on railroad carriers its own version of reasonable service requirements could hardly be more at odds with the uniformity contemplated by Congress in enacting the Interstate Commerce Act.” Id., at 326. To hold otherwise, we said, would merely approve “an attempt by a disappointed shipper to gain from the Iowa courts the relief it was denied by the Commission.” Id., at 324.

In the case before us, the Louisiana Supreme Court’s award of damages to respondents was necessarily supported by an assumption that the higher rate respondents might have filed with the Commission was reasonable. Otherwise, there would have been no basis for that court’s conclusion, 368 *581So. 2d, at 991, that the Commission would have approved the rate. But under the filed rate doctrine, the Commission alone is empowered to make that judgment, and until it has done so, no rate other than the one on file may be charged. And far from approving the rate here in issue, the Commission has expressly declined to speculate on what its predecessor might have done.11 The court below, like the state *582court in Kalo Brick, has consequently usurped a function that Congress has assigned to a federal regulatory body. This the Supremacy Clause will not permit.

Respondents’ theory of the case would give inordinate importance to the role of contracts between buyers and sellers in the federal scheme for regulating the sale of natural gas. Of course, as we have held on more than one occasion, nothing in the Act forbids parties to set their rates by contract. E. g., Permian Basin Area Rate Cases, 390 U. S. 747, 820-822 (1968); United Gas Pipe Line Co. v. Mobile Gas Service Corp., 350 U. S. 332, 338-340 (1956). But those cases stand only for the proposition that the Commission itself lacks affirmative authority, absent extraordinary circumstances, to “abrogate existing contractual arrangements.” Permian Basin Area Rate Cases, supra, at 820. See United Gas Pipe Line Co. v. Mobile Gas Service Corp., supra, at 338-339. That rule does not affect the supremacy of the Act itself, and under the filed rate doctrine, when there is a conflict between the filed rate and the contract rate, the filed rate controls. See, e. g., Louisville :& Nashville R. Co. v. Maxwell, 237 U. S. 94, 97 (1915); Texas & Pacific R. Co. v. Mugg, 202 U. S. 242, 245 (1906). “This rule is undeniably strict, and it obviously may work hardship in some cases, but it embodies the policy which has been adopted by Congress . . . .” Louisville & Nashville R. Co. v. Maxwell, supra, at 97. Moreover, to permit parties to vary by private agreement the rates filed with the Commission would undercut the clear purpose of the congressional scheme: granting the Commission an opportunity in every case to judge the reasonableness of the rate. Cf. United Gas Pipe Line Co. v. Mobile Gas Service Corp., supra, at 338-339.12

*583Respondents also appeal to what they say are equitable considerations. The filed rate doctrine and the Supremacy Clause, we are told, should not bar recovery when the defendant’s misconduct prevented filing of a higher rate. We do not find this argument compelling. The court below did not find that Arkla intentionally failed to inform respondents of its lease payments to the United States in an effort to defraud them. Consequently, we are not faced with affirmative misconduct, and we need not consider the application of the filed rate doctrine in such a case.13 The courts *584below found that Arkla has done no more than commit a simple breach of its contract. But when a court is called upon .to decide whether state and federal laws are in conflict, the fact that the state law has been violated does not affect the analysis. Every pre-emption case involves a conflict between a claim of right under federal law and a claim of right under state law. A finding that federal law provides a shield for the challenged conduct will almost always leave the state-law violation unredressed. Thus in San Diego Building Trades Council v. Garmon, 359 U. S. 236 (1959), the mere fact that a group of unions violated state law through their peaceful picketing did not permit enforcement of that law when it would conflict with the federal regulatory scheme. That the state-court suit was one for damages rather than for the type of relief available from the National Labor Relations Board weighed against pre-emption, not in favor of it. “[S]ince remedies form an ingredient of any integrated scheme of regulation,” Justice Frankfurter wrote for the Court, “to allow the State to grant a remedy here which has been withheld from the National Labor Relations Board only accentuates the danger of conflict.” Id., at 247.

The same principle applies here. Permitting the state court to award what amounts to a retroactive right to collect a rate in excess of the filed rate “only accentuates the danger of conflict.” No appeal to equitable principles can justify this usurpation of federal authority.

Ill

We hold that the filed rate doctrine prohibits the award of damages for Arkla’s breach during the period that respondents were subject to Commission jurisdiction.14 In all respects other than those relating to damages, the judgment of the Supreme Court of Louisiana is affirmed. With respect *585to its calculation of damages, the judgment is vacated, and the case is remanded for further proceedings not inconsistent with this opinion.

So ordered.

Justice Stewart took no part in the consideration or decision of this case.

with whom Justice Rehnquist joins, dissenting.

From 1961 through 1975, petitioner Arkansas Louisiana Gas Co. (Arkla) acquired natural gas from two different sources in the Sligo Gas Field in Louisiana. By the terms of a contract that was entirely consistent with the federal policies reflected in the Natural Gas Act, 52 Stat. 821, as amended, 15 U. S. C. § 717 et seq. (1976 ed. and Supp. Ill), Arkla was obligated to pay both sources of supply the same price.1 In fact, however, unbeknown to respondents, and in violation of their contract, Arkla paid them a substantially lower price than it paid to the United States, its other source for Sligo Field gas. No one, not even Arkla, suggests that there is any legitimate justification for the discrimination.

Despite the fact that Arkla breached its contract, and despite the fact that no federal policy is threatened by allowing the Louisiana courts to redress that breach, the Court today denies respondents the benefit of their lawful bargain. Surely, if the price paid to the United States was just and reasonable, the same price paid to private sellers of gas taken from the same field at the same time and delivered to the same customer also would be just and reasonable. The statutory policy favors uniformity, not secret discrimination. *587Yet the Court, by a wondrous extension of the so-called “filed rate doctrine,” concludes that the Louisiana courts may not assess damages against petitioner for breach of its contract to pay respondents the same price it paid to a comparable supplier. Because no federal rule of law deprives the State of Louisiana of the power to prevent Arkla from profiting so handsomely from its own wrong, and because I believe that enforcement of the state court’s judgment is not only consistent with federal regulatory policies, but actually will further those policies, I respectfully dissent.

I

As a result of lengthy proceedings in the state courts, the relevant facts have been established. Arkla is an integrated utility company engaged in the natural gas business in six States.2 Over the years, it has purchased large quantities of natural gas produced in the Sligo Gas Field in Bossier Parish, La.; some of that gas was acquired from respondents, and some from the United States. By law, Arkla was prohibited from paying either of these suppliers more than the area Ceiling price set by the Federal Power Commission, and it did not do so.3 By contract with the United States, Arkla was required to pay an amount established by reference “to the highest price paid for a part or for a majority of production of like quality in the same field.” App. 123. By contract with respondents, Arkla was obligated to pay them a price at least as high as it paid for other gas produced from any well *588located in the Sligo Field.4 See ante, at 573-574, n. 2. In fact, however, it paid respondents only about two-thirds of the price paid to the United States.

Arkla did not disclose the price differential to respondents. The Louisiana Court of Appeal found that, in response to inquiries from respondents about the arrangement with the United States, “the officials of Arkla were uncooperative and evasive.” 359 So. 2d 255, 264 (1978). That court characterized Arkla’s nondisclosure and evasiveness as “not commendable,” but held that because, under the law of Louisiana, a “party alleging fraud has the burden of establishing it by more than a mere preponderance of the evidence,” respondents had failed to prove that Arkla was guilty of actual fraud. Ibid. It is clear, however, that Arkla’s failure to disclose to respondents its discriminatory payments to another supplier in the same gas field constituted a breach of contract.5

The Louisiana Supreme Court decided that the damages for Arkla’s breach of contract should be measured by the difference between the price paid to the United States and the price paid to respondents. For the period after 1972, when *589respondents had been formally certificated as “small producers,” the court held that respondents had no obligation to file new rate schedules with the Federal Power Commission because the increased rates did not exceed the ceiling rate set by the Commission.6 Although the court recognized that respondents could not have collected higher prices during the period between 1961 and 1972 without first filing new rate schedules with the Commission,7 it held that damages for that period were nevertheless recoverable for two reasons. First, as a matter of Louisiana law, when a party’s entitlement is subject to a condition, the condition is considered to have been fulfilled when performance is prevented by the other party.8 In this case, the court squarely held that respondents had been effectively precluded from making the *590necessary filings by Arkla’s failure to inform them of its contractual arrangement with the United States.9 Second, after noting that respondents made no claim that they would have been entitled to an increase in excess of the area base rate ceilings established by the Commission,10 and after noting that an order of the Commission had indicated that it would have approved the rate increase if it had been filed,11 the court concluded that “it was more probable than not that the Commission would have approved a contractually-authorized price increase if the proper filing procedures had been followed.” 368 So. 2d 984, 991 (1979).

Summarizing the effect of the state courts’ rulings, these *591propositions must be taken as having been established: (1) Arkla breached its contract with respondents; (2) Arkla is responsible for respondents’ failure to file new rate schedules with the Commission; (3) if such schedules had been filed, and if Arkla had paid respondents the same prices it paid to the United States, those prices would not have exceeded the applicable area rate ceilings established by the Commission; and (4) because prices well below the applicable rate ceilings are at the very least presumptively “just and reasonable,” it is indeed more probable than not that the Commission would have approved the new rate schedule if it had been promptly filed. These propositions are plainly adequate to support respondents’ recovery of damages as a matter of state law. In my opinion, they also support the conclusion that the applicable rules of state law have not been pre-empted by federal law.

II

Section 4 of the Natural Gas Act, 52 Stat. 822, 15 U. S. C. § 717c, identifies four separate federal policies that are arguably implicated by this litigation. The judgment of the Supreme Court of Louisiana is fully consistent with each of these policies.

First, subsection (a) of § 4 requires that all charges paid or received by regulated companies for the sale of.natural gas shall, be “just and reasonable.” 12 In this case, there is no dispute about the fact that the prices received from Arkla by the United States were well below the relevant area ceiling rates fixed by the Federal Power Commission. It is equally clear that payment of the same prices to respondents for com*592parable gas contemporaneously produced in the same field also would have been well below the ceiling. Both the Louisiana courts and the Commission have repeatedly and unambiguously determined that if respondents had been paid in accordance with the terms of their contract, there would have been no violation of the applicable area ceiling rates.13 Indeed, in noting that respondents were not required to file new rates for the period after they had been certificated as small producers in 1972, the Commission expressly found “that the rates requested are within what the Commission has determined to be the zone of reasonableness.” 14

*593It is perfectly clear that an award of damages against Arkla measured by the prices it paid to the United States will not violate the Act’s substantive prohibition against charging rates that are not “just and reasonable.” That prohibition has the same application to respondents for the period after 1972, when they were certificated as small producers, as it does for the period prior to 1972. In neither of those periods did the Commission specifically determine that the rates were “just and reasonable,” but the record makes it clear that those rates were in fact within the zone of reasonableness established by the Commission during both periods. For the purpose of determining whether damages are recoverable in a state-court breach-of-contract suit, there is no reason to treat the two periods differently. There is simply nothing in this record to suggest that a state-court judgment that has the effect of allowing respondents to receive the same prices that Arkla paid to the United States would violate the substantive policy underlying the statutory requirement that all rates be just and reasonable.15

*594Second, subsection (b) of § 4 expresses the strong federal policy — reflected in most regulatory statutes — against discriminatory pricing.16 The result the Court reaches today not only tolerates a blatant violation of that policy, but also will encourage such violations in the future.

Entirely apart from Arida’s contractual undertaking to pay respondents the same price it paid to other producers of comparable gas in the same field, this statutory policy surely favors a holding that results in equal treatment of competing suppliers. Nothing other than Arkla’s proven wrongdoing provides any explanation for its discrimination against respondents. For no one has pointed to any even .arguably legitimate justification for any differential pricing at all — let alone a differential of the magnitude revealed by this record. The lesson this case will teach is that, notwithstanding the plain language in § 4 (b), it is perfectly proper to grant an undue preference if one can conceal it.

Third, subsection (c) of § 4 expresses a policy favoring the public disclosure of all rates and charges and all contracts which affect rates.17 The contractual arrangement between *595Arkla and the United States relating to production in the Sligo Gas Field was not made available to the public. Only by resort to the remedies provided by the Freedom of Information Act were respondents able to obtain access to that contract and to confirm their suspicions that Arkla was violating its “favored nations” undertaking. By rewarding Arkla’s successful concealment of a contract that directly affected rates payable for gas produced in the Sligo Field, the Court simply ignores the statutory policy which the Louisiana Supreme Court’s judgment would plainly serve.

Fourth, subsection (d) of § 4 imposes a procedural requirement that is designed to protect the substantive policy interests reflected in the three preceding subsections.18 Because none of these substantive policies is infringed in the slightest by the state court’s judgment, it surely exalts procedure over substance to deny respondents relief because they were wrongfully prevented from following the normal statutory procedures.

Under the normal procedures, no change in rates may take effect until after 30 days’ notice is given to the Commission and to the public by filing a new schedule with the Commission. This filing requirement is designed to give the Commission the opportunity to prevent new rates from going into effect if it has reason to believe the new rates are not just and *596reasonable. In this case, if the record provided any basis for believing that the rates that Arkla paid to the United States were not just and reasonable — or that paying the same rates to these respondents would not have been equally just and reasonable — it might make some sense to argue that the filing requirement of § 4 (d) precludes recovery of damages for breach of contract. But to regard the filing requirement as an inflexible barrier to any recovery regardless of the substantive merits of the claim is neither necessary to further, nor even consistent with, the purpose of § 4 (d).19

It is commonplace that damages must often be measured by reference to a standard or an event that did not actually materialize. When an executory contract is breached, the attempt to measure the injured party’s damages requires an evaluation of the benefits that probably would have resulted if the breach had not occurred.20 If an attorney hired by *597respondents to file a new rate schedule negligently failed to do so, he might defend against a malpractice complaint by arguing that respondents were not damaged because the Commission would have rejected the new rates in all events. But if respondents could prove that rejection was highly unlikely, it would be absurd to deny them any recovery at all simply because the defendant’s own wrongdoing had made it impossible to know with absolute certainty that new rates would have been accepted as “just and reasonable.” In damages actions, whether in tort or in breach of contract, it is often necessary to deal in probabilities.

This case also raises a question that requires the evaluation of probabilities. Because the rates in issue were below the applicable Commission ceilings, and because no legitimate reason for rejecting them has been adduced, it is only reasonable to presume that they would have become effective routinely. As a garden-variety issue of damages, there is no significant difference between this case and one in which a purchaser might have employed thugs to waylay the respondents’ lawyer on the way to the Commission to prevent him from filing a new schedule.

Nor in terms of federal regulatory policy is there any difference between this case and hypothetical cases involving actual fraud or violence/21 If damages cannot be measured *598by reference to any standard except a rate that has been duly filed with the Commission in accordance with the procedural requirements of § 4 (d), there could be no state-law recovery no matter what kind of wrong prevented respondents from filing. And conversely, if a high probability that a timely filing would have been accepted is an adequate standard for measuring damages in a tort case, why should not that probability be adequate in a breach-of-contract case as well? The fact that a regulated carrier or seller has no right to collect a rate or price that has not been duly filed with the appropriate regulatory body is surely not a sufficient reason for leaping to the conclusion that an injured party may never prove damages by reference to a standard that is less certain than a filed rate.

The federal policy that comes closest to supporting Arkla’s position is that of protecting the Commission’s primary jurisdiction to determine whether or not a new rate is reasonable. But in this case the basic reasonableness determination was made by the Commission when it established the area rate ceilings. Because the rates at issue in this case are well below those ceilings, the danger that a court might venture into the area of ratemaking on its own is not present. Moreover, on more than one occasion Arkla requested the Commission to assume jurisdiction of this controversy, and the Commission consistently declined to do so.22 In assessing damages for the breach of an executory contract, the state courts exercised a jurisdiction that the Commission did not have. In no sense did the Louisiana courts usurp the primary jurisdiction of the Commission. In sum, whether we test the state-court judgment against the substantive or the procedural requirements of the federal statute, it seems perfectly clear that the relief that has been awarded is fully consistent with federal policy.

*599III

Although, until today, the term “filed rate doctrine” had never been used by this Court, our prior decisions have established rather clear contours for the doctrine. It apparently encompasses two components, both of which are entirely consistent with the award of damages ordered by the Louisiana Supreme Court in this case.

First, the two cases that are generally accepted' as the source of the doctrine, Montana-Dakota Utilities Co. v. Northwestern Public Service Co., 341 U. S. 246,23 and T. I. M. E. Inc. v. United States, 359 U. S. 464,24 established that an *600entity whose prices or rates are regulated by a federal agency has no federal right to claim any rate or price that has not been filed with and approved by the agency. Thus, these respondents, without either filing the escalated rates or obtaining a waiver of the filing requirement, have no federal right to require Arkla to pay the higher rates. That does not mean, however, that they have no contractual right to require Arkla to do so. Cf. Pan American Petroleum Corp. v. Superior Court, 366 U. S. 656, 662-664. The question whether a state court could measure damages for breach of contract, or a tort, by reference to a rate schedule that presumably would have been accepted if it had been filed earlier is by no means the same as the question whether respondents had a federal right to collect such rates. There would be a valid federal objection to such a damages award if there were reason to believe that the parties had entered into an agreement to circumvent either a procedural or a substantive requirement of the Natural Gas Act, or if the litigation arguably represented a collusive method of granting an unlawful preference. But no such considerations are present in this case.

Second, Montana-Dakota Utilities and T. I. M. E. Inc. also recognize that the task of determining in the first instance what rate should be considered “reasonable” within the meaning of a regulatory statute is not a judicial task, but rather is a task for the administrative agency. But when the zone of reasonableness has already been established by an agency— *601as it has been in this case — that consideration simply does not apply to an award of damages measured by reference to a standard that is well within that zone.

In my judgment, the cases which gave rise to the filed rate doctrine are plainly distinguishable from the present case, and thus do not support the result the Court reaches today. In Montana-Dakota Utilities and T. I. M. E. Inc., the plaintiff’s claim was that the filed rate, which had already been approved by the relevant federal regulatory body, was nonetheless unreasonable in violation of federal statutory requirements.25 The plaintiff’s suit thus directly challenged the rate determinations of the federal agency without compliance with the judicial review procedures established in the governing statute.26 In the present case, in contrast, respondents do not contend that the filed rate, approved by the Commission, is unreasonable or otherwise inconsistent with federal law; they contend only that they had a contractual right to receive a different reasonable rate under their contract with Arkla. Respondents do not seek to enforce a federal right outside *602the procedures established for the vindication of such rights, nor do they seek to overturn the determinations of the expert federal agency; respondents merely seek to recover the higher of two rates, both of which are within the federal zone of reasonableness, because it is the rate they contracted to receive.27 Cf. Hewitt-Robins Inc. v. Eastern Freight-Ways, Inc., 371 U. S. 84.

The unanimous decision in United Gas Pipe Line Co. v. Mobile Gas Service Co., 350 U. S. 332, sheds more light on this case than do the cases on which the Court places its primary reliance. In United Gas, United, a regulated natural gas producer, supplied gas to Mobile under a long-term contract which had been filed with and approved by the Federal Power Commission. United thereafter filed with the Commission a new rate that purported to increase the price payable by Mobile under the contract. The Commission denied Mobile’s request that it reject United’s filing, and held that the increased rate was the applicable rate unless and until it was declared unlawful by the Commission. Id., at 336-337. This Court rejected the Commission’s position, holding that compliance with the filing procedure of § 4 (d) was effective to establish a new rate only if that rate were otherwise lawful, that is, in compliance with contractual requirements. Id., at 339-340. The Court found that although the new rate filed by United had been established in compliance with fed*603eral law, it was unlawful under the contract. The Court accordingly held that the Commission had erred in failing to reject United’s filing, and directed that United make restitution to Mobile of all overpayments. Id., at 347.

Under the rationale in United Gas, private parties have a right to establish a lawful rate by contract as long as the rate they have agreed upon is just and reasonable. When the contract rate is within the zone of reasonableness established by the Commission, that contract rate is presumptively lawful,28 and not subject to unilateral change.29 The Commission has no power to specify a rate other than the contract rate when that rate is itself just and reasonable.30 Neither the filed rate *604doctrine, nor any other principle of federal regulatory law, requires the result the Court announces today.

IV

In an attempt to bolster its reliance on the filed rate doctrine, Arkla contends that we cannot be sure that, if respondents had been notified of the United States lease and had filed a new rate schedule in 1961, the Commission would have approved their new rates. This argument is supported by statements in an order entered by the Commission on November 5, 1980.31 That order was entered after the petition for certiorari had been filed, and after the United States and the Commission had taken the position as amici in this Court *605that the Louisiana Supreme Court had erred in awarding damages for the period between 1961 and 1972.32 Because the Commission had decided to lend its support to Arkla in this Court, it is not surprising that some of the statements in that order are consistent with Arkla’s argument. What is most significant about that order is the fact that the Commission does not advance any reason why a rate schedule filed by respondents in 1961 in accordance with the favored nations clause of their contract with Arkla would not have been deemed just and reasonable.

Although the Commission stated that it was reluctant to speculate about what its predecessors might have done in response to such a filing, the only issues that it now can describe as speculative are issues that have been decided against Arkla. I do not believe speculation that the Commission might have committed error in 1961 is an adequate reason for not presuming that just and reasonable rates would have been routinely approved when filed.

The first issue on which the Commission indicates a reluctance to speculate is a question of contract interpretation, namely, whether the favored nations clause had been triggered by Arkla’s arrangement with the United States. There is no reason for the Commission, or anyone else, to speculate on this question. The Commission twice was presented with the opportunity to decide this question, and it twice declined *606to do so.33 That question now has been correctly resolved by the Louisiana courts. The other issue on which the Commission declines to speculate is whether its predecessor would have regarded a favored nations clause in a pre-1961 contract as lawful. Again, speculation is wholly unnecessary. The Commission actually confronted that precise issue in 1961. Although it concluded that such escalation clauses should be prohibited in the future, it specifically decided that it would not eliminate such provisions from previously executed contracts.34 That the Commission’s treatment of that issue in *6071961 is applicable to the contracts between respondents and Arkla is demonstrated by the fact that the escalated rates are accepted by the Court and the Commission for the purpose of computing respondents’ damages for the period between 1972 and 1975. If the favored nations clause in this pre-1961 contract were not perfectly lawful, respondents would receive no damages at all, rather than the truncated recovery which the Court’s holding today allows.

The Commission also has expressed concern about the impact of this damages award on its broader “regulatory responsibilities.” See Arkansas Louisiana Gas Co. v. Hall, 13 FERC ¶ 61,100, p. 61,213 (1980). Two specific concerns are identified — that the burden of the award might be passed on to consumers, and that it might give rise to other claims that favored nations clauses have been breached. The short answer to the first concern is that there is no more reason to assume that this award will justify an increase in utility rates than any other damages judgment that a public utility may be required to pay; if the regulatory concern is valid, the agency having jurisdiction over Arkla’s sales has ample authority to require its stockholders rather than its customers to bear this additional cost. The second concern seems exaggerated because it applies only to contracts executed before 1961, see supra, at 606 and this page, and n. 34, and it seems unlikely that many large purchasers of natural gas could successfully have concealed violations of escalation clauses from their suppliers. To the extent that this case does have counterparts in such contracts, however, it seems to me *608that those cases should be decided in the same way. After all, we are concerned here merely with cases in which a utility has failed to pay an agreed price that is well below the just and reasonable ceiling set by the Commission.

I agree that speculation about what the Commissioners might have done in 1961 is inappropriate. Unlike the Court, however, I see no need to speculate in this case. Rather than speculate, I would presume that the Commission would have acted in a lawful manner and that it would then have perceived the correct answer to disputed questions that have subsequently been resolved.

In my judgment, the Court’s decision today is founded on nothing more than the mechanical application to this case of principles developed in other contexts to serve other purposes. The Court commits manifest error by applying the filed rate doctrine to ratify action by Arkla that not only breached its contract with respondents, but also directly undercut the substantive policies identified in § 4 of the Natural Gas Act. Because absolutely no federal interest is served by today’s intrusion into state contract law, I respectfully dissent.

dissenting.

I agree with much of Justice Stevens’ dissenting opinion and would affirm the judgment of the Supreme Court of Louisiana. Respondents are entitled to the relief they seek based on Louisiana state contract law.

By virtue of the “most favored nations” clause in its contract with respondents, petitioner was obligated to pay respondents the higher rate it paid a comparable supplier. Petitioner did not comply with this provision, but the Court today holds that respondents nevertheless may not recover damages because they failed to file with the Commission the increased rate. It is said that the “filed rate doctrine” requires such a filing.

I would agree with the Court if it were clear that respondents were neglectful or otherwise at fault in not filing and seeking Commission approval of the higher rate. But the Louisiana courts found that petitioner was responsible for respondents’ failure to file. Petitioner did not disclose that it was paying higher rates to another producer from the same field under comparable conditions. The .Louisiana Court of Appeal expressly found that respondents’ failure to comply with the filed rate doctrine was caused primarily by the “uncooperative and evasive” conduct of petitioner’s officials. See 359 So. 2d 255, 264 (1978). Petitioner knew the facts, and the Louisiana Supreme Court held that petitioner had a state-law duty to disclose them in order not to frustrate the “most favored nations” clause. There is no showing that respond*586ents had any knowledge of their entitlement to invoke the clause until they finally obtained the facts through the Freedom of Information Act. In these circumstances, the filed rate doctrine should not preclude a state-law damages action. In holding to the contrary, the Court in effect rewards petitioner’s breach of its state-law contractual duty to notify respondents that it was paying a higher rate to a comparable supplier.