sary to ensure the development and continued existence of adequate wood processing capacity in that State for the sustained utilization of timber from the National Forests which are geographically isolated from other processing facilities." 36 CFR § 223.10(c) (1983).

From 1969 to 1973, Congress imposed a maximum export limitation of 350 million board-feet of unprocessed timber from federal lands lying west of the 100th meridian (a line running from central North Dakota through central Texas). 16 U. S. C. §617(a). Beginning in 1973, Congress imposed, by way of a series of annual riders to appropriation Acts, a complete ban on foreign exports of unprocessed logs from western lands except those within Alaska. See, e. g., Pub. L. 96-126, Tit. III, §301, 93 Stat. 979. These riders limit only foreign exports and do not require in-state processing before the timber may be sold in domestic interstate commerce. The export limitation with respect to federal land in Alaska, rather than being imposed by statute, was imposed by the above-quoted regulation, and applies to exports to other States, as well as to foreign exports.

Alaska argues that federal statutes and regulations demonstrate an affirmative expression of approval of its primarymanufacture requirement for three reasons: (1) federal timber export policy has, since 1928, treated federal timber land in Alaska differently from that in other States; (2) the Federal Government has specifically tailored its policies to ensure development of wood-processing capacity for utilization of timber from the National Forests; and (3) the regulation forbidding without prior approval the export from Alaska of unprocessed timber or its shipment to other States demonstrates that it is the Alaska wood-processing industry in particular, not the domestic wood-processing industry generally, that has been the object of federal concern.

Acceptance of Alaska's three factual propositions does not mandate acceptance of its conclusion. Neither South

Central nor the United States challenges the existence of a federal policy to restrict the out-of-state shipment of unprocessed Alaska timber from federal lands. They challenge only the derivation from that policy of an affirmative expression of federal approval of a parallel policy with respect to state timber. They argue that our cases dealing with congressional authorization of otherwise impermissible state interference with interstate commerce have required an "express" statement of such authorization, and that no such authorization may be implied.

It is true that most of our cases have looked for an express statement of congressional policy prior to finding that state regulation is permissible. For example, in Sporhase v. Nebraska ex rel. Douglas, supra, the Court declined to find congressional authorization for state-imposed burdens on interstate commerce in ground water despite 37 federal statutes and a number of interstate compacts that demonstrated Congress' deference to state water law. We noted that on those occasions in which consent has been found, congressional intent and policy to insulate state legislation from Commerce Clause attack have been "expressly stated." 458 U. S., at 960. Similarly, in New England Power Co. v. New Hampshire, 455 U. S. 331 (1982), we rejected a claim by the State of New Hampshire that its restriction on the interstate flow of privately owned and produced electricity was authorized by § 201(b) of the Federal Power Act. That section provides that the Act "shall not . . . deprive a State or State commission of its lawful authority now exercised over the exportation of hydroelectric energy which is transmitted across a State line." 16 U. S. C. § 824(b). We found nothing in the statute or legislative history "evinc[ing] a congressional intent 'to alter the limits of state power otherwise imposed by the Commerce Clause."" 455 U. S., at 341

"The United States appears as amicus curiae in support of the position of South-Central.

(quoting United States v. Public Utilities Comm'n of California, 345 U. S. 295, 304 (1953)).

Alaska relies in large part on this Court's recent opinion in White v. Massachusetts Council of Construction Employers, Inc., 460 U. S. 204 (1983), for its "implicit approval" theory. At issue in White was an executive order issued by the Mayor of Boston requiring all construction projects funded by the city or by funds that the city had authority to administer, to be performed by a work force consisting of at least 50% residents of the city. A number of the projects were funded in part with federal Urban Development Action Grants. The Court held that insofar as the city expended its own funds on the projects, it was a market participant unconstrained by the dormant Commerce Clause; insofar as the city expended federal funds, "the order was affirmatively sanctioned by the pertinent regulations of those programs." Id., at 215. Alaska relies on the Court's statements in White that the federal regulations "affirmatively permit" and "affirmatively sanctio[n]" the executive order and that the order "sounds a harmonious note" with the federal regulations, and it finds significance in the fact that the Court did not use the words "expressly stated."

Rather than supporting the position of the State, we believe that White undermines it. If approval of state burdens on commerce could be implied from parallel federal policy, the Court would have had no reason to rely upon the marketparticipant doctrine to uphold the executive order. Instead, the order could have been upheld as being in harmony with federal policy as expressed in regulations governing the expenditure of federal funds.

There is no talismanic significance to the phrase "expressly stated," however; it merely states one way of meeting the requirement that for a state regulation to be removed from the reach of the dormant Commerce Clause, congressional intent must be unmistakably clear. The requirement that Congress affirmatively contemplate otherwise invalid state legis

lation is mandated by the policies underlying dormant Commerce Clause doctrine. It is not, as Alaska asserts, merely a wooden formalism. The Commerce Clause was designed "to avoid the tendencies toward economic Balkanization that had plagued relations among the Colonies and later among the States under the Articles of Confederation." Hughes v. Oklahoma, 441 U. S. 322, 325 (1979). Unrepresented interests will often bear the brunt of regulations imposed by one State having a significant effect on persons or operations in other States. Thus, "when the regulation is of such a character that its burden falls principally upon those without the state, legislative action is not likely to be subjected to those political restraints which are normally exerted on legislation where it affects adversely some interests within the state." South Carolina State Highway Dept. v. Barnwell Brothers, Inc., 303 U. S. 177, 185, n. 2 (1938); see also Southern Pacific Co. v. Arizona, 325 U. S., at 767-768, n. 2. On the other hand, when Congress acts, all segments of the country are represented, and there is significantly less danger that one State will be in a position to exploit others. Furthermore, if a State is in such a position, the decision to allow it is a collective one. A rule requiring a clear expression of approval by Congress ensures that there is, in fact, such a collective decision and reduces significantly the risk that unrepresented interests will be adversely affected by restraints on commerce."

The fact that the state policy in this case appears to be consistent with federal policy—or even that state policy furthers the goals we might believe that Congress had in mind—is an insufficient indicium of congressional intent. Congress acted only with respect to federal lands; we cannot infer from that fact that it intended to authorize a similar policy with respect

'The need for affirmative approval is heightened by the fact that Alaska's policy has substantial ramifications beyond the Nation's borders. The need for a consistent and coherent foreign policy, which is the exclusive responsibility of the Federal Government, enhances the necessity that congressional authorization not be lightly implied.

We now turn to the issues left unresolved by the Court of Appeals. The first of these issues is whether Alaska's restrictions on export of unprocessed timber from state-owned lands are exempt from Commerce Clause scrutiny under the "market-participant doctrine."

Our cases make clear that if a State is acting as a market participant, rather than as a market regulator, the dormant Commerce Clause places no limitation on its activities. See White v. Massachusetts Council of Construction Employers, Inc., 460 U. S., at 206-208; Reeves, Inc. v. Stake, 447 U. S. 429, 436-437 (1980); Hughes v. Alexandria Scrap Corp., 426 U. S. 794, 810 (1976). The precise contours of the marketparticipant doctrine have yet to be established, however, the doctrine having been applied in only three cases of this Court to date.

The first of the cases, Hughes v. Alexandria Scrap Corp., supra, involved a Maryland program designed to reduce the number of junked automobiles in the State. A "bounty" was established on Maryland-licensed junk cars, and the State imposed more stringent documentation requirements on out

It is for that reason that we need not resolve the dispute between the parties about whether Congress' purpose in applying the primary-manufacture requirement to federal lands was for the purpose of encouraging the Alaska wood-processing industry or whether it was merely to ensure adequate processing capacity to deal with federal timber. In either event, no congressional intent to permit a primary-manufacture requirement by the State appears.

It is worthy of note, although we do not rely upon it, that Congress has been requested to authorize the imposition by States of in-state processing requirements but has declined to do so. Prohibit Export of Unprocessed Timber: Hearing on H. R. 639 before the Subcommittee on Forests, Family Farms, and Energy of the House Committee on Agriculture, 97th Cong., 1st Sess., 18-19 (1981).