JUSTICE BRENNAN delivered the opinion of the Court:In 1977, the Minnesota Legislature enacted a statute banning the retail sale of milk in plastic nonreturnable, nonrefillable containers, but permitting such sale in other nonreturnable, nonrefillable containers, such as paperboard milk cartons.  1977 Minn. Laws, ch. 268, Minn.Stat. § 116 F. 21 (1978).  Respondents [Footnote 1] contend that the statute violates the Equal Protection and Commerce Clauses of the Constitution.IThe purpose of the Minnesota statute is set out as § 1:"The legislature finds that the use of nonreturnable, nonrefillable containers for the packaging of milk and other milk products presents a solid waste management problem for the state, promotes energy waste, and depletes natural resources.  The legislature therefore, in Page 449 U. S. 459 furtherance of the policies stated in Minnesota Statutes, Section 116 F. 01, [Footnote 2] determines that the use of nonreturnable, nonrefillable containers for packaging milk and other milk products should be discouraged, and that the use of returnable and reusable packaging for these products is preferred, and should be encouraged."1977 Minn.Laws, ch. 268, § 1, codified as Minn.Stat. § 116 F. 21 (1978).  Section 2 of the Act forbids the retail sale of milk and fluid milk products, other than sour cream, cottage cheese, and yogurt, in nonreturnable, nonrefillable rigid or semirigid containers composed at least 50% of plastic. [Footnote 3]The Act was introduced with the support of the state Pollution Control Agency, Department of Natural Resources, Department of Agriculture, Consumer Services Division, and Energy Agency, [Footnote 4] and debated vigorously in both houses of the state legislature.  Proponents of the legislation argued that it would promote resource conservation, ease solid waste disposal problems, and conserve energy.  Relying on the results of studies and other information, [Footnote 5] they stressed the need to Page 449 U. S. 460 stop introduction of the plastic nonreturnable container before it became entrenched in the market.  Opponents of the Act, also presenting empirical evidence, argued that the Act would not promote the goals asserted by the proponents, but would merely increase costs of retail milk products and prolong the use of ecologically undesirable paperboard milk cartons.After the Act was passed, respondents filed suit in Minnesota District Court, seeking to enjoin its enforcement.  The court conducted extensive evidentiary hearings into the Act's probable consequences, and found the evidence "in sharp conflict."  App. A-25.  Nevertheless, finding itself "as factfinder . . . obliged to weigh and evaluate this evidence," ibid., the court resolved the evidentiary conflicts in favor of respondents, and concluded that the Act "will not succeed in effecting the Legislature's published policy goals. . . ."  Id. at A-21.  The court further found that, contrary to the statement of purpose in § 1, the "actual basis" for the Act"was to promote the economic interests of certain segments of the local dairy and pulpwood industries at the expense of the economic interests of other segments of the dairy industry and the plastics industry."Id. at A-19.  The court therefore declared the Act "null, void, and unenforceable" and enjoined its enforcement, basing the judgment on substantive due process under the Fourteenth Amendment to the United States Constitution and Art. 1 § 7, of the Minnesota Constitution; equal protection under the Fourteenth Amendment; and prohibition of unreasonable burdens on interstate commerce under Art. I, § 8, of the United States Constitution.  App. A-23.The State appealed to the Supreme Court of Minnesota, which affirmed the District Court on the federal equal protection and due process grounds, without reaching the Commerce Clause or state law issues.  289 N.W.2d 79 (1979).  Unlike the District Court, the State Supreme Court found that the purpose of the Act was"to promote the state interests Page 449 U. S. 461 of encouraging the reuse and recycling of materials and reducing the amount and type of material entering the solid waste stream,"and acknowledged the legitimacy of this purpose.  Id. at 82.  Nevertheless, relying on the District Court's findings of fact, the full record, and an independent review of documentary sources, the State Supreme Court held that "the evidence conclusively demonstrates that the discrimination against plastic nonrefillables is not rationally related to the Act's objectives."  Ibid.  We granted certiorari, 445 U.S. 949, and now reverse.IIThe parties agree that the standard of review applicable to this case under the Equal Protection Clause is the familiar "rational basis" test.  See Vance v. Bradley, 440 U. S. 93,  440 U. S. 97 (1979); New Orleans v. Dukes, 427 U. S. 297,  427 U. S. 303 (1976). [Footnote 6]  Moreover, they agree that the purposes of the Act Page 449 U. S. 462 cited by the legislature -- promoting resource conservation, easing solid waste disposal problems, and conserving energy -- are legitimate state purposes.  Thus, the controversy in this Page 449 U. S. 463 case centers on the narrow issue whether the legislative classification between plastic and nonplastic nonreturnable milk containers is rationally related to achievement of the statutory purposes. [Footnote 7]ARespondents apparently have not challenged the theoretical connection between a ban on plastic nonreturnables and the purposes articulated by the legislature; instead, they have argued that there is no empirical connection between the two.  They produced impressive supporting evidence at trial to prove that the probable consequences of the ban on plastic nonreturnable milk containers will be to deplete natural resources, exacerbate solid waste disposal problems, and waste energy, because consumers unable to purchase milk in plastic Page 449 U. S. 464 containers will turn to paperboard milk cartons, allegedly a more environmentally harmful product.But States are not required to convince the courts of the correctness of their legislative judgments.  Rather,"those challenging the legislative judgment must convince the court that the legislative facts on which the classification is apparently based could not reasonably be conceived to be true by the governmental decisionmaker.""Vance v. Bradley, 440 U.S.  at 111.  See also Day-Brite Lighting, Inc. v. Missouri, 342 U. S. 421,  342 U. S. 425 (1952); Henderson Co. v. Thompson, 300 U. S. 258,  300 U. S. 264-265 (1937)."Although parties challenging legislation under the Equal Protection Clause may introduce evidence supporting their claim that it is irrational, United States v. Carolene Products Co., 304 U. S. 144,  304 U. S. 153-154 (1938), [Footnote 8] they cannot prevail so long as"it is evident from all the considerations presented to [the legislature], and those of which we may take judicial notice, that the question is at least debatable."Id. at  304 U. S. 154.  Where there was evidence before the legislature reasonably supporting the classification, litigants may not procure invalidation of the legislation merely by tendering evidence in court that the legislature was mistaken.The District Court candidly admitted that the evidence was "in sharp conflict," App. A-25, but resolved the conflict in favor of respondents and struck down the statute.  The Supreme Court of Minnesota, however, did not reverse on the basis of this patent violation of the principles governing rationality analysis under the Equal Protection Clause.  Rather, the court analyzed the statute afresh under the Equal Protection Clause, and reached the conclusion that the statute is Page 449 U. S. 465 constitutionally invalid.  The State contends that, in this analysis, the court impermissibly substituted its judgment for that of the legislature.  We turn now to that argument.BThe State identifies four reasons why the classification between plastic and nonplastic nonreturnables is rationally related to the articulated statutory purposes.  If any one of the four substantiates the State's claim, we must reverse the Minnesota Supreme Court and sustain the Act.First, the State argues that elimination of the popular plastic milk jug will encourage the use of environmentally superior containers.  There is no serious doubt that the plastic containers consume energy resources and require solid waste disposal, nor that refillable bottles and plastic pouches are environmentally superior.  Citing evidence that the plastic jug is the most popular, and the gallon paperboard carton the most cumbersome and least well regarded package in the industry, the State argues that the ban on plastic nonreturnables will buy time during which environmentally preferable alternatives may be further developed and promoted.As Senator Spear argued during the Senate debate:"[T]his bill is designed to prevent the beginning of another system of non-returnables that is going to be very, very difficult [to stop] once it begins.  It is true that our alternative now is not a returnable system in terms of milk bottles.  Hopefully we are eventually going to be able to move to that kind of a system, but we are never going to move to a returnable system so long as we allow another nonreturnable system with all the investment and all of the vested interest that that is going to involve to begin."Transcript of the Full Senate Floor Discussion of H.F. 45, p. 6 (May 20, 1977), reprinted as Plaintiffs' Exhibit J.  Accord, id. at 1-2 (statement of Sen. Luther). Page 449 U. S. 466The Minnesota Supreme Court dismissed this asserted state interest as "speculative and illusory."  289 N.W.2d  at 86.  The court expressed doubt that the Minnesota Legislature or Pollution Control Agency would take any further steps to promote environmentally sound milk packaging, and stated that there is no evidence that paperboard cartons will cease to be used in Minnesota.  Ibid.We find the State's approach fully supportable under our precedents.  This Court has made clear that a legislature need not "strike at all evils at the same time or in the same way," Semler v. Oregon State Board of Dental Examiners, 294 U. S. 608,  294 U. S. 610 (1935), and that a legislature"may implement [its] program step by step, . . . adopting regulations that only partially ameliorate a perceived evil and deferring complete elimination of the evil to future regulations.""New Orleans v. Dukes, 427 U.S. at  427 U. S. 303.  See also Katzenbach v. Morgan, 384 U. S. 641,  384 U. S. 657 (1966); Williamson v. Lee Optical Co., 348 U. S. 483,  348 U. S. 489 (1955); Railway Express Agency, Inc. v. New York, 336 U. S. 106,  336 U. S. 110 (1949).  The Equal Protection Clause does not deny the State of Minnesota the authority to ban one type of milk container conceded to cause environmental problems, merely because another type, already established in the market, is permitted to continue in use.  Whether in fact the Act will promote more environmentally desirable milk packaging is not the question:  the Equal Protection Clause is satisfied by our conclusion that the Minnesota Legislature could rationally have decided that its ban on plastic nonreturnable milk jugs might foster greater use of environmentally desirable alternatives."Second, the State argues that its ban on plastic nonreturnable milk containers will reduce the economic dislocation foreseen from the movement toward greater use of environmentally superior containers.  The State notes that plastic nonreturnables have only recently been introduced on a wide scale in Minnesota, and that, at the time the legislature was Page 449 U. S. 467 considering the Act, many Minnesota dairies were preparing to invest large amounts of capital in plastic container production.  As Representative Munger, chief sponsor of the bill in the House of Representatives, explained:"Minnesota's dairy market is on the verge of making a major change over from essentially a paperboard container system to a system of primarily single use, throwaway plastic bottles.  The major dairies in our state have ordered the blow-mold equipment to manufacture in plant the nonreturnable plastic milk bottle.  Members of the House, I feel now is an ideal time for this legislation when only one dairy in our state is firmly established in manufacturing and marketing the throwaway plastic milk bottle."Transcript of the Debate of the Minnesota House of Representatives on H.F. 45, p. 2 (Mar. 10, 1977), reprinted as Plaintiffs' Exhibit J.  See also Transcript of the Full Senate Floor Discussion on H.F. 45, p. 6 (May 20, 1977), reprinted as Plaintiffs' Exhibit J (statement of Sen. Milton); id. at 9 (statement of Sen. Schaaf); id. at 10-11 (statement of Sen. Perpich).Moreover, the State explains, to ban both the plastic and the paperboard nonreturnable milk container at once would cause an enormous disruption in the milk industry, because few dairies are now able to package their products in refillable bottles or plastic pouches.  Thus, by banning the plastic container while continuing to permit the paperboard container, the State was able to prevent the industry from becoming reliant on the new container, while avoiding severe economic dislocation.The Minnesota Supreme Court did not directly address this justification, but we find it supported by our precedents as well.  In New Orleans v. Dukes, supra, we upheld a city regulation banning pushcart food vendors, but exempting from the ban two vendors who had operated in the city for over eight years.  Noting that the "city could reasonably decide Page 449 U. S. 468 that newer businesses were less likely to have built up substantial reliance interests in continued operation," we held that the city "could rationally choose initially to eliminate vendors of more recent vintage."  Id. at  427 U. S. 305.  Accord, United States v. Maryland Savings-Share Ins. Corp., 400 U. S. 4,  400 U. S. 6 (1970).  This case is not significantly different.  The state legislature concluded that nonreturnable, nonrefillable milk containers pose environmental hazards, and decided to ban the most recent entry into the field.  The fact that the legislature in effect "grandfathered" paperboard containers, at least temporarily, does not make the Act's ban on plastic nonreturnables arbitrary or irrational.Third, the State argues that the Act will help to conserve energy.  It points out that plastic milk jugs are made from plastic resin, an oil and natural gas derivative, whereas paperboard milk cartons are primarily composed of pulpwood, which is a renewable resource.  This point was stressed by the Act's proponents in the legislature.  Senator Luther commented:"We have been through an energy crisis in Minnesota.  We know what it is like to go without and what we are looking at here is a total blatant waste of petroleum and natural gas. . . ."Transcript of the Full Senate Floor Discussion on H. F. 45, p. 12 (May 20, 1977), reprinted as Plaintiffs' Exhibit J.  Representative Munger said in a similar vein:"A sweep to the plastic throwaway bottle in the gallon size container alone would use enough additional natural gas and petroleum to heat 3,100 homes each year in Minnesota when compared to a refillable system and 1,400 compared to the present paperboard system.  Plastic containers are made from a non-renewable resource, while the paperboard is made from Minnesota's forest products."Transcript of the Debate of the Minnesota House of Representatives on H.F. 45, p. 2 (Mar. 10, 1977), reprinted as Plaintiffs' Exhibit J. Page 449 U. S. 469The Minnesota Supreme Court held, in effect, that the legislature misunderstood the facts.  The court admitted that the results of a reliable study [Footnote 9] support the legislature's conclusion that less energy is consumed in the production of paperboard containers than in the production of plastic nonreturnables, but, after crediting the contrary testimony of respondents' expert witness and altering certain factual assumptions, [Footnote 10] the court concluded that "production of plastic nonrefillables requires less energy than production of paper containers."  289 N.W.2d  at 85.The Minnesota Supreme Court may be correct that the Act is not a sensible means of conserving energy.  But we reiterate that "it is up to legislatures, not courts, to decide on the wisdom and utility of legislation."  Ferguson v. Skrupa, 372 U. S. 726,  372 U. S. 729 (1963).  Since, in view of the evidence before the legislature, the question clearly is "at least debatable," United States v. Carolene Products Co., 304 U.S. at  304 U. S. 154, the Minnesota Supreme Court erred in substituting its judgment for that of the legislature.Fourth, the State argues that the Act will ease the State's solid waste disposal problem.  Most solid consumer wastes in Minnesota are disposed of in landfills.  A reputable study before the Minnesota Legislature indicated that plastic milk jugs occupy a greater volume in landfills than other nonreturnable milk containers. [Footnote 11]  This was one of the legislature's major concerns.  For example, in introducing the bill to the House of Representatives, Representative Munger asked rhetorically:  Page 449 U. S. 470 "Why do we need this legislation?"  Part of his answer to the query as that "the plastic non-refillable containers will increase the problems of solid waste in our state."  Transcript of the Debate of the Minnesota House of Representatives on H.F. 45, p. 1 (Mar. 10, 1977), reprinted as Plaintiffs' Exhibit J.The Minnesota Supreme Court found that plastic milk jugs in fact take up less space in landfills and present fewer solid waste disposal problems than do paperboard containers.  289 N.W.2d  at 82-85.  But its ruling on this point must be rejected for the same reason we rejected its ruling concerning energy conservation:  it is not the function of the courts to substitute their evaluation of legislative facts for that of the legislature.We therefore conclude that the ban on plastic nonreturnable milk containers bears a rational relation to the State's objectives, and must be sustained under the Equal Protection Clause. [Footnote 12]IIIThe District Court also held that the Minnesota statute is unconstitutional under the Commerce Clause [Footnote 13] because it imposes an unreasonable burden on interstate commerce. [Footnote 14]  We cannot agree. Page 449 U. S. 471When legislating in areas of legitimate local concern, such as environmental protection and resource conservation, States are nonetheless limited by the Commerce Clause.  See Lewis v. BT Investment Managers, Inc., 447 U. S. 27,  447 U. S. 36 (1980); Hunt v. Washington Apple Advertising Comm'n, 432 U. S. 333,  432 U. S. 350 (1977); Southern Pacific Co. v. Arizona ex rel. Sullivan, 325 U. S. 761,  325 U. S. 767 (1945).  If a state law purporting to promote environmental purposes is in reality "simple economic protectionism," we have applied a "virtually per se rule of invalidity."  Philadelphia v. New Jersey, 437 U. S. 617,  437 U. S. 624 (1978). [Footnote 15]  Even if a statute regulates "evenhandedly," and imposes only "incidental" burdens on interstate commerce, the courts must nevertheless strike it down if "the burden imposed on such commerce is clearly excessive in relation to the putative local benefits."  Pike v. Bruce Church, Inc., 397 U. S. 137,  397 U. S. 142 (1970).  Moreover,"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."Ibid.Minnesota's statute does not effect "simple protectionism," but "regulates evenhandedly" by prohibiting all milk retailers from selling their products in plastic, nonreturnable milk containers, without regard to whether the milk, the containers, Page 449 U. S. 472 or the sellers are from outside the State.  This statute is therefore unlike statutes discriminating against interstate commerce, which we have consistently struck down.  E.g., Lewis v. BT Investment Managers, Inc., supra, (Florida statutory scheme prohibiting investment advisory services by bank holding companies with principal offices out of the State); Hughes v. Oklahoma, 441 U. S. 322 (1979) (Oklahoma statute prohibiting the export of natural minnows from the State); Philadelphia v. New Jersey, supra, (New Jersey statute prohibiting importation of solid and liquid wastes into the State); Hunt v. Washington Apple Advertising Comm'n, supra (North Carolina statute imposing additional costs on Washington, but not on North Carolina, apple shippers) .Since the statute does not discriminate between interstate and intrastate commerce, the controlling question is whether the incidental burden imposed on interstate commerce by the Minnesota Act is "clearly excessive in relation to the putative local benefits."  Pike v. Bruce Church, Inc., supra at  397 U. S. 142.  We conclude that it is not.The burden imposed on interstate commerce by the statute is relatively minor.  Milk products may continue to move freely across the Minnesota border, and since most dairies package their products in more than one type of containers, [Footnote 16] the inconvenience of having to conform to different packaging requirements in Minnesota and the surrounding States should be slight.  See Pacific States Box & Basket Co. v. White, 296 U. S. 176,  296 U. S. 184 (1935).  Within Minnesota, business will presumably shift from manufacturers of plastic nonreturnable containers to producers of paperboard cartons, refillable bottles, Page 449 U. S. 473 and plastic pouches, but there is no reason to suspect that the gainers will be Minnesota firms, or the losers out-of-state firms.  Indeed, two of the three dairies, the sole milk retailer, and the sole milk container producer challenging the statute in this litigation are Minnesota firms. [Footnote 17]Pulpwood producers are the only Minnesota industry likely to benefit significantly from the Act at the expense of out-of-state firms.  Respondents point out that plastic resin, the raw material used for making plastic nonreturnable milk jugs, is produced entirely by non-Minnesota firms, while pulpwood, used for making paperboard, is a major Minnesota product.  Nevertheless, it is clear that respondents exaggerate the degree of burden on out-of-state interests, both because plastics will continue to be used in the production of plastic pouches, plastic returnable bottles, and paperboard itself, and because out-of-state pulpwood producers will presumably absorb some of the business generated by the Act.Even granting that the out-of-state plastics industry is burdened relatively more heavily than the Minnesota pulpwood industry, we find that this burden is not "clearly excessive" in light of the substantial state interest in promoting conservation of energy and other natural resources and easing solid waste disposal problems, which we have already reviewed in the context of equal protection analysis.  See supra at  449 U. S. 465-470.  We find these local benefits ample to support Minnesota's decision under the Commerce Clause.  Moreover, we find that no approach with "a lesser impact on interstate activities," Pike v. Bruce Church, Inc., supra at  397 U. S. 142, is available.  Respondents have suggested several alternative statutory schemes, but these alternatives are either more burdensome on commerce than the Act (as, for example, banning all nonreturnables) or less likely to be effective (as, for example, Page 449 U. S. 474 providing incentives for recycling).  See Brief for Respondents 32-33.In Exxon Corp. v. Governor of Maryland, 437 U. S. 117 (1978), we upheld a Maryland statute barring producers and refiners of petroleum products -- all of which were out-of-state businesses -- from retailing gasoline in the State.  We stressed that the Commerce Clause "protects the interstate market, not particular interstate firms, from prohibitive or burdensome regulations."  Id. at  437 U. S. 127-128.  A nondiscriminatory regulation serving substantial state purposes is not invalid simply because it causes some business to shift from a predominantly out-of-state industry to a predominantly in-state industry.  Only if the burden on interstate commerce clearly outweighs the State's legitimate purposes does such a regulation violate the Commerce Clause.The judgment of the Minnesota Supreme Court isReversed
U.S. Supreme CourtMinnesota v. Clover Leaf Creamery Co., 449 U.S. 456 (1981)Minnesota v. Clover Leaf Creamery Co.No. 79-1171Argued November 3, 1980Decided January 21, 1981449 U.S. 456SyllabusFor the stated purposes of promoting resource conservation, easing solid waste disposal problems, and conserving energy, the Minnesota Legislature enacted a statute banning the retail sale of milk in plastic nonreturnable, nonrefillable containers, but permitting such sale in other nonreturnable, nonrefillable containers, such as paperboard cartons.  Respondents filed suit in Minnesota District Court, seeking to enjoin enforcement of the statute on constitutional grounds.  The District Court held that the statute violated, inter alia, the Equal Protection Clause of the Fourteenth Amendment and the Commerce Clause.  Finding that "the evidence conclusively demonstrate[d] that the discrimination against plastic nonrefillables [was] not rationally related to the Act's objectives," the Minnesota Supreme Court affirmed on the equal protection ground without reaching the Commerce Clause issue.Held:1. The ban on plastic nonreturnable milk containers bears a rational relation to the State's objectives, and must be sustained under the Equal Protection Clause.  Pp.  449 U. S. 461-470.(a) The Equal Protection Clause does not deny Minnesota the authority to ban one type of milk container conceded to cause environmental problems merely because another already established type is permitted to continue in use.  Whether in fact the statute will promote more environmentally desirable milk packaging is not the question.  The Equal Protection Clause is satisfied if the Minnesota Legislature could rationally have decided that its ban on plastic milk jugs might foster greater use of environmentally desirable alternatives.  Pp.  449 U. S. 465-466.(b) The fact that the state legislature, having concluded that nonreturnable, nonrefillable milk containers pose environmental hazards, decided to ban the most recent entry in the field, and thus, in effect, "grandfathered" paperboard containers, at least temporarily, does not make the ban on plastic containers arbitrary or irrational.  Cf. New Orleans v. Dukes, 427 U. S. 297.  Pp.  449 U. S. 466-468.(c) Where the evidence as to whether the statute would help to conserve energy was "at least debatable," the Minnesota Supreme Court erred in substituting its judgment for that of the legislature by finding, contrary to the legislature, that the production of plastic nonrefillable Page 449 U. S. 457 containers required less energy than production of paper containers.  Pp.  449 U. S. 468-69.(d) Similarly, the Minnesota Supreme Court erred in finding, contrary to the legislature's finding based on a reputable study, that plastic milk jugs take up less space in landfills and present fewer solid waste disposal problems than do paperboard containers.  Pp.  449 U. S. 469-470.2. The statute does not violate the Commerce Clause as constituting an unreasonable burden on interstate commerce.  Pp.  449 U. S. 470-474.(a) The statute does not discriminate between interstate and intrastate commerce, but regulates evenhandedly by prohibiting all milk retailers from selling their products in plastic containers, without regard to whether the milk, the containers, or the sellers are from outside the State.  Pp.  449 U. S. 471-472.(b) The incidental burden imposed on interstate commerce by the statute is not excessive in relation to the putative local benefits.  Milk products may continue to move freely across the Minnesota border, and since most dairies package their products in more than one type of container, the inconvenience of having to conform to different packaging requirements in Minnesota and the surrounding States should be slight.  Even granting that the out-of-state plastics industry is burdened relatively more heavily than the Minnesota pulpwood industry, this burden is not "clearly excessive" in light of the substantial state interest in promoting conservation of energy and other natural resources and easing solid waste disposal problems.  These local benefits amply support Minnesota's decision under the Commerce Clause.  Pp.  449 U. S. 472-474.289 N.W.2d 79, reversed.BRENNAN, J., delivered the opinion of the Court, in which BURGER, C.J., and STEWART, WHITE, MARSHALL, and BLACKMUN, JJ., joined.  POWELL, J., filed an opinion concurring in part and dissenting in part, post, p.  449 U. S. 474.  STEVENS, J., filed a dissenting opinion, post, p.  449 U. S. 477.  REHNQUIST, J., took no part in the consideration or decision of the case. Page 449 U. S. 458