reconcile modern Commerce Clause concepts with several old cases of this Court holding that States can prohibit the importation of some objects because they "are not legitimate subjects of trade and commerce." Bowman v. Chicago & Northwestern R. Co., 125 U. S. 465, 489. These articles include items "which, on account of their existing condition, would bring in and spread disease, pestilence, and death, such as rags or other substances infected with the germs of yellow fever or the virus of small-pox, or cattle or meat or other provisions that are diseased or decayed, or otherwise, from their condition and quality, unfit for human use or consumption." Ibid. See also Baldwin v. G. A. F. Seelig, Inc., 294 U. S. 511, 525, and cases cited therein. The state court found that ch. 363 as narrowed by the state regulations, see n. 2, supra, banned only "those wastes which can [not] be put to effective use," and therefore those wastes were not commerce at all, unless "the mere transportation and disposal of valueless waste between states constitutes interstate commerce within the meaning of the constitutional provision." 68 N. J., at 468, 348 A. 2d, at 514.

We think the state court misread our cases, and thus erred in assuming that they require a two-tiered definition of commerce. In saying that innately harmful articles "are not legitimate subjects of trade and commerce," the Bowman Court was stating its conclusion, not the starting point of its reasoning. All objects of interstate trade merit Commerce Clause protection; none is excluded by definition at the outset. In Bowman and similar cases, the Court held simply that because the articles' worth in interstate commerce was far outweighed by the dangers inhering in their very movement, States could prohibit their transportation across state lines. Hence, we reject the state court's suggestion that the banning of "valueless" out-of-state wastes by ch. 363 implicates no constitutional protection. Just as Congress has power to regulate the interstate movement of these wastes, States are

not free from constitutional scrutiny when they restrict that movement. Cf. Hughes v. Alexandria Scrap Corp., 426 U. S. 794, 802-814; Meat Drivers v. United States, 371 U. S. 94.

III
A

Although the Constitution gives Congress the power to regulate commerce among the States, many subjects of potential federal regulation under that power inevitably escape congressional attention "because of their local character and their number and diversity." South Carolina State Highway Dept. v. Barnwell Bros., Inc., 303 U. S. 177, 185. In the absence of federal legislation, these subjects are open to control by the States so long as they act within the restraints imposed by the Commerce Clause itself. See Raymond Motor Transportation, Inc. v. Rice, 434 U. S. 429, 440. The bounds of these restraints appear nowhere in the words of the Commerce Clause, but have emerged gradually in the decisions of this Court giving effect to its basic purpose. That broad purpose was well expressed by Mr. Justice Jackson in his opinion for the Court in H. P. Hood & Sons, Inc. v. Du Mond, 336 U. S. 525, 537-538:

"This principle that our economic unit is the Nation, which alone has the gamut of powers necessary to control of the economy, including the vital power of erecting customs barriers against foreign competition, has as its corollary that the states are not separable economic units. As the Court said in Baldwin v. Seelig, 294 U. S. [511], 527, 'what is ultimate is the principle that one state in its dealings with another may not place itself in a position of economic isolation." "

The opinions of the Court through the years have reflected an alertness to the evils of "economic isolation" and protectionism, while at the same time recognizing that incidental

burdens on interstate commerce may be unavoidable when a State legislates to safeguard the health and safety of its people. Thus, where simple economic protectionism is effected by state legislation, a virtually per se rule of invalidity has been erected. See, e. g., H. P. Hood & Sons, Inc., v. Du Mond, supra; Toomer v. Witsell, 334 U. S. 385, 403-406; Baldwin v. G. A. F. Seelig, Inc., supra; Buck v. Kuykendall, 267 U. S. 307, 315-316. The clearest example of such legislation is a law that overtly blocks the flow of interstate commerce at a State's borders. Cf. Welton v. Missouri, 91 U. S. 275. But where other legislative objectives are credibly advanced and there is no patent discrimination against interstate trade, the Court has adopted a much more flexible approach, the general contours of which were outlined in Pike v. Bruce Church, Inc., 397 U. S. 137, 142:

"Where the statute regulates evenhandedly to effectuate
a legitimate local public interest, and its effects on inter-
state commerce are only incidental, it will be upheld
unless the burden imposed on such commerce is clearly
excessive in relation to the putative local benefits.
If a legitimate local purpose is found, then the question
becomes one of degree. And the extent of the burden
that will be tolerated will of course depend on the nature
of the local interest involved, and on whether it could be
promoted as well with a lesser impact on interstate
activities."

See also Raymond Motor Transportation, Inc. v. Rice, supra, at 441-442; Hunt v. Washington Apple Advertising Comm'n, 432 U. S. 333, 352–354; Great A&P Tea Co. v. Cottrell, 424 U. S. 366, 371–372.

The crucial inquiry, therefore, must be directed to determining whether ch. 363 is basically a protectionist measure, or whether it can fairly be viewed as a law directed to legitimate local concerns, with effects upon interstate commerce that are only incidental.

The purpose of ch. 363 is set out in the statute itself as follows:

"The Legislature finds and determines that . . . the volume of solid and liquid waste continues to rapidly increase, that the treatment and disposal of these wastes continues to pose an even greater threat to the quality of the environment of New Jersey, that the available and appropriate land fill sites within the State are being diminished, that the environment continues to be threatened by the treatment and disposal of waste which originated or was collected outside the State, and that the public health, safety and welfare require that the treatment and disposal within this State of all wastes generated outside of the State be prohibited."

The New Jersey Supreme Court accepted this statement of the state legislature's purpose. The state court additionally found that New Jersey's existing landfill sites will be exhausted within a few years; that to go on using these sites or to develop new ones will take a heavy environmental toll, both from pollution and from loss of scarce open lands; that new techniques to divert waste from landfills to other methods of disposal and resource recovery processes are under development, but that these changes will require time; and finally, that "the extension of the lifespan of existing landfills, resulting from the exclusion of out-of-state waste, may be of crucial importance in preventing further virgin wetlands or other undeveloped lands from being devoted to landfill purposes." 68 N. J., at 460-465, 348 A. 2d, at 509-512. Based on these findings, the court concluded that ch. 363 was designed to protect, not the State's economy, but its environment, and that its substantial benefits outweigh its "slight" burden on interstate commerce. Id., at 471-478, 348 A. 2d, at 515–519.

The appellants strenuously contend that ch. 363, "while outwardly cloaked 'in the currently fashionable garb of environ

Opinion of the Court

437 U.S. mental protection,' . . . is actually no more than a legislative effort to suppress competition and stabilize the cost of solid waste disposal for New Jersey residents . . . ." They cite passages of legislative history suggesting that the problem addressed by ch. 363 is primarily financial: Stemming the flow of out-of-state waste into certain landfill sites will extend their lives, thus delaying the day when New Jersey cities must transport their waste to more distant and expensive sites.

The appellees, on the other hand, deny that ch. 363 was motivated by financial concerns or economic protectionism. In the words of their brief, "[n]o New Jersey commercial interests stand to gain advantage over competitors from outside the state as a result of the ban on dumping out-of-state waste." Noting that New Jersey landfill operators are among the plaintiffs, the appellee's brief argues that "[t]he complaint is not that New Jersey has forged an economic preference for its own commercial interests, but rather that it has denied a small group of its entrepreneurs an economic opportunity to traffic in waste in order to protect the health, safety and welfare of the citizenry at large."

This dispute about ultimate legislative purpose need not be resolved, because its resolution would not be relevant to the constitutional issue to be decided in this case. Contrary to the evident assumption of the state court and the parties, the evil of protectionism can reside in legislative means as well as legislative ends. Thus, it does not matter whether the ultimate aim of ch. 363 is to reduce the waste disposal costs of New Jersey residents or to save remaining open lands from pollution, for we assume New Jersey has every right to protect its residents' pocketbooks as well as their environment. And it may be assumed as well that New Jersey may pursue those ends by slowing the flow of all waste into the State's remaining landfills, even though interstate commerce may incidentally be affected. But whatever New Jersey's ultimate purpose, it may not be accomplished by discriminating against