Appellants argue, however, that this fact does show that the Maryland statute impermissibly burdens interstate commerce. They point to evidence in the record which indicates that, because of the divestiture requirements, at least three refiners will stop selling in Maryland, and which also supports their claim that the elimination of company-operated stations will deprive the consumer of certain special services. Even if we assume the truth of both assertions, neither warrants a finding that the statute impermissibly burdens interstate commerce.

Some refiners may choose to withdraw entirely from the Maryland market, but there is no reason to assume that their share of the entire supply will not be promptly replaced by other interstate refiners. The source of the consumers' supply may switch from company-operated stations to independent dealers, but interstate commerce is not subjected to an impermissible burden simply because an otherwise valid regulation causes some business to shift from one interstate supplier to another.

The crux of appellants' claim is that, regardless of whether the State has interfered with the movement of goods in interstate commerce, it has interfered "with the natural functioning of the interstate market either through prohibition or through burdensome regulation." Hughes v. Alexandria Scrap Corp., 426 U. S. 794, 806. Appellants then claim that the statute "will surely change the market structure by weakening the independent refiners. . . ." 17 We cannot, however, accept appellants' underlying notion that the Commerce Clause protects the particular structure or methods of operation in a retail market. See Breard v. Alexandria, 341 U. S. 622. As indicated by the Court in Hughes, the Clause protects the interstate market, not particular interstate firms, from prohib

the flow of interstate commerce as the sales made by the refiner-operated stations.

17 Reply Brief for Appellants in No. 77-64, p. 7.

itive or burdensome regulations. It may be true that the consuming public will be injured by the loss of the highvolume, low-priced stations operated by the independent refiners, but again that argument relates to the wisdom of the statute, not to its burden on commerce.

Finally, we cannot adopt appellants' novel suggestion that because the economic market for petroleum products is nationwide, no State has the power to regulate the retail marketing of gas. Appellants point out that many state legislatures have either enacted or considered proposals similar to Maryland's," and that the cumulative effect of this sort of legislation may have serious implications for their national marketing operations. While this concern is a significant one, we do not find that the Commerce Clause, by its own force, pre-empts the field of retail gas marketing. To be sure, "the Commerce Clause acts as a limitation upon state power even without congressional implementation." Hunt v. Washington Apple Advertising Comm'n, supra, at 350. But this Court has only rarely held that the Commerce Clause itself pre-empts an entire field from state regulation, and then only when a lack of national uniformity would impede the flow of interstate goods. See Wabash, St. L. & P. R. Co. v. Illinois, 118 U. S. 557; see also Cooley v. Board of Wardens, 12 How. 299, 319. The evil that appellants perceive in this litigation is not that the several States will enact differing regulations, but rather that they will all conclude that divestiture provisions are warranted. The problem thus is not one of national uniformity. In the absence of a relevant congressional declaration of policy, or a showing of a specific discrimination against, or burdening

18 California, Delaware, the District of Columbia, and Florida have adopted laws restricting refiners' operation of service stations. Similar proposals have been before the legislatures of 32 other jurisdictions. See Brief for Appellants in No. 77-10, p. 45 nn. 21 and 22; Brief for the State of California as Amicus Curiae.

of, interstate commerce, we cannot conclude that the States are without power to regulate in this area.

IV

Exxon, Phillips, Shell, and Gulf contend that the requirement that voluntary allowances be extended to all retail service stations is either in direct conflict with § 2 (b) of the Clayton Act, as amended by the Robinson-Patman Act, or, more generally, in conflict with the basic federal policy in favor of competition, which is reflected in the Sherman Act as well as § 2 (b). In rejecting these contentions, the Maryland Court of Appeals noted that the Maryland statute covered two different competitive situations.19 In the first situation a competing retailer lowers its price on its own, and the oil company gives its own retailer a price reduction to enable it to meet that lower price. In the second situation, the competing retailer's lower price is subsidized by its supplier, and the oil company gives its own retailer a price reduction to meet the competition. The good-faith defense of § 2 (b) is clearly not available to the oil company in the first situation because the voluntary allowance would not be a response to competition from another oil company. See FTC v. Sun Oil Co., 371 U .S. 505. In the second situation the law is unsettled,20 but the

10 The Court of Appeals also noted that there is a third competitive situation a discriminatory price reduction made to meet an equally low price offered to the same buyer by a competing seller. In the lower court's view, this situation clearly fell within the §2 (b) defense, but was not encompassed by the term "voluntary allowances." 279 Md., at 452, 370 A. 2d, at 1125.

20 The Court left the question open in Sun Oil, 371 U. S., at 512 n. 7, and the lower courts have reached conflicting results. Compare Enterprise Industries v. Texas Co., 136 F. Supp. 420 (Conn. 1955), rev'd on other grounds, 240 F. 2d 457 (CA2 1957), cert. denied, 353 U. S. 965, with Bargain Car Wash, Inc. v. Standard Oil Co. (Indiana), 466 F. 2d 1163 (CA7 1972).

Court of Appeals concluded that the defense would also be unavailable. The court therefore reasoned that there was no conflict between the Maryland statute and § 2 (b), since the statute did not apply to any allowance protected by federal law. In our opinion, it is not necessary to decide whether the § 2 (b) defense would apply in the second situation, for even assuming that it does, there is no conflict between the Maryland statute and the Robinson-Patman Act sufficient to require pre-emption.

Appellants' first argument is that compliance with the Maryland statute may cause them to violate the RobinsonPatman Act. They stress the possibility that the requirement that a price reduction be made on a statewide basis may result in discrimination between customers who would otherwise receive the same price, and they describe various hypothetical situations to illustrate this point." But, "[i]n this as in other areas of coincident federal and state regulation, the 'teaching of this Court's decisions . . . enjoin [s] seeking out conflicts between state and federal regulation where none clearly exists.' Huron Cement Co. v. Detroit, 362 U. S. 440, 446.” Seagram & Sons, Inc. v. Hostetter, 384 U. S. 35, 45. See also State v. Tetaco, Inc., 14 Wis. 2d 625, 111 N. W. 2d 918 (1961). The Court in Seagram & Sons went on to say that "[a]lthough it is possible to envision circumstances under which price dis

"1 Appellants argue that compliance with the "voluntary allowance" provision may expose them to both primary-line and secondary-line liability under §2 (a) of the Clayton Act, as amended by the Robinson-Patman Act. With respect to primary-line liability, they pose the hypothesis of a seller who responds to a competitor's lower price in Baltimore. Under the statute, he must lower his prices throughout the State, even though the competitive market justifying that price is confined to Baltimore. Appellants then argue that a competitor operating only in Salisbury, Md., may be injured by this price reduction. But an injury flowing from a uniform price reduction is not actionable under the Robinson-Patman Act, which only prohibits price discrimination. See F. Rowe, Price Discrimination Under the Robinson-Patman Act 93 (1962).

criminations proscribed by the Robinson-Patman Act might be compelled by [the state statute], the existence of such potential conflicts is entirely too speculative in the present posture of this case" to warrant pre-emption. 384 U. S., at 46. That counsel of restraint applies with even greater force here. For even if we were to delve into the hypothetical situations posed by appellants, we would not be presented with a state statute that requires a violation of the Robinson-Patman Act. Instead, the alleged "conflict" here is in the possibility that the Maryland statute may require uniformity in some situations in which the Robinson-Patman Act would permit localized discrimination.22 This sort of hypothetical conflict is not sufficient to warrant pre-emption.

Appellants, however, also claim that the Robinson-Patman Act does not simply permit localized discrimination, but actually establishes a federal right to engage in discriminatory pricing in certain situations. They argue that this federal right may be found directly in § 2 (b), or, more generally, in our Nation's basic policy favoring competition as reflected in the Sherman Act as well as § 2 (b). We find neither argument persuasive.

The proviso in § 2 (b) of the Clayton Act, as amended by

22 Thus, appellants' claim that the statute will create secondary-line liability is premised on the possibility that price differentials may arise between stations located in Maryland and those in neighboring States. With respect to this claim, it is sufficient to note that, although the Maryland statute may affect the business decision of whether or not to reduce prices, it does not create any irreconcilable conflict with the RobinsonPatman Act. The statute may require that a voluntary allowance that could legally have been confined to the Baltimore area be extended to Salisbury. We may then assume, arguendo, that the Robinson-Patman Act could require a further extension of the allowance into the neighboring State. The possible scope of the voluntary allowance may, therefore, have an impact on the company's decision on whether or not to meet the competition in Baltimore, but the state statute does not in any way require discriminatory prices. See also n. 20, supra.