dissenting.
While the Court in this case seems to do nothing more than apply well-established equal protection and Commerce Clause principles to a particular state statute, in reality its reversal of the Minnesota Supreme Court is based upon a newly discovered principle of federal constitutional law. According to this principle, which is applied but not explained by the majority, the Federal Constitution defines not only the relationship between Congress and the federal courts, but also the relationship between state legislatures and state courts. Because I can find no support for this novel constitutional doctrine in either the language of the Federal Constitution or the prior decisions of this Court, I respectfully dissent.
I
The keystone of the Court’s equal protection analysis is its pronouncement that “it is not the function of the courts to substitute their evaluation of legislative facts for that of the legislature.” Ante, at 470.1 If the pronouncement concerned *478the function of federal courts, it would be amply supported by reason and precedent. For federal tribunals are courts of limited jurisdiction, whose powers are confined by the Federal Constitution, by statute, and by the decisions of this Court. It is not surprising, therefore, that the Court’s pronouncement is supported by citation only to precedents dealing with the function that a federal court may properly perform when it is reviewing the constitutionality of a law enacted by Congress or by a state legislature.2
*479But what is the source — if indeed there be one — of this Court’s power to make the majestic announcement that it is not the function of a state court to substitute its evaluation of legislative facts for that of a state legislature? I should have thought the allocation of functions within the structure of a state government would be a matter for the State to determine. I know of nothing in the Federal Constitution that prohibits a State from giving lawmaking power to its courts.3 *480Nor is there anything in the Federal Constitution that prevents a state court from reviewing factual determinations made by a state legislature or any other state agency.4 If a state statute expressly authorized a state tribunal to sit as a Council of Revision with full power to modify or to amend *481the work product of its legislature, that statute would not violate any federal rule of which I am aware. The functions that a state court shall perform within the structure of state government are unquestionably matters of state law.
One of the few propositions that this Court has respected with unqualified consistency — until today — is the rule that a federal court is bound to respect the interpretation of state law announced by the highest judicial tribunal in a State.5 In this case, the Minnesota Supreme Court has held that the state trial court acted properly when it reviewed the factual basis for the state legislation, and implicitly the Minnesota Supreme Court also has held that its own review of the legislative record was proper. Moreover, it also has determined as a matter of state law how it properly should resolve conflicts in the evidence presented to the state legislature, as supplemented by the additional evidence presented to the trial court in this case.6 In my opinion, the factual conclu*482sions drawn by the Minnesota courts concerning the deliberations of the Minnesota Legislature are entitled to just as much deference as if they had been drafted by the state legislature itself and incorporated in a preamble to the state statute. The State of Minnesota has told us in unambiguous language that this statute is not rationally related to any environmental objective; it seems to me to be a matter of indifference, for purposes of applying the federal Equal Protection Clause, whether that message to us from the State of Minnesota is conveyed by the State Supreme Court, or by the state legislature itself.
I find it extraordinary that this federal tribunal feels free to conduct its own de novo review of a state legislative record in search of a rational basis that the highest court of the State has expressly rejected. There is no precedent in this Court’s decisions for such federal oversight of a State’s lawmaking process.7 Of course, if a federal trial court had reviewed the *483factual basis for a state law, conflicts in the evidence would have to be resolved in favor of the State.8 But when a state court has conducted the review, it is not our business to dis*484agree with the state tribunal’s evaluation of the State’s own lawmaking process. Even if the state court should tell us that a state statute has a meaning that we believe the state *485legislature plainly did not intend, we are not free to take our own view of the matter.9
Once it is recognized that this Court may not review the question of state law presented by the Minnesota courts’ decision to re-evaluate the evidence presented to the legislature, the result we must reach in this case is apparent. Because the factual conclusions drawn by the Minnesota courts are clearly supported by the record,10 the only federal issue that this case presents is whether a discriminatory statute that is *486admittedly irrational violates the Equal Protection Clause of the Fourteenth Amendment. The Court implicitly acknowledges that the Minnesota Supreme Court applied the proper rule of federal law when it answered that question.11 Whatever we may think about the environmental consequences of this discriminatory law, it follows inexorably that it is our duty as federal judges to affirm the judgment of the Minnesota Supreme Court.
II
In light of my conclusion that the Minnesota Supreme Court’s equal protection decision must be affirmed, I need not address the Commerce Clause question resolved by the majority. Ante, at 470-474. Nonetheless, I believe that the majority’s treatment of that question compels two observations.
First, in my opinion the Court errs in undertaking to decide the Commerce Clause question at all. The state trial court addressed the question and found that the statute was designed by the Minnesota Legislature to promote the economic interests of the local dairy and pulpwood industries at the expense of competing economic groups.12 On appeal, the *487Minnesota Supreme Court expressly declined to consider this aspect of the trial court’s decision, and accordingly made no comment at all upon the merits of the Commerce Clause question. 289 N. W. 2d 79, 87, n. 20 (1979). Generally, when reviewing state-court decisions, this Court will not decide questions which the highest court of a State has properly declined to address. The majority offers no persuasive explanation for its unusual action in this case.13 In the absence *488of some substantial justification for this action, I would not deprive the Minnesota Supreme Court of the first opportunity to review this aspect of the decision of the Minnesota trial court.
Second, the Court's Commerce Clause analysis suffers from the same flaw as its equal protection analysis. The Court rejects the findings of the Minnesota trial court, - not because they are clearly erroneous, but because the Court is of the view that the Minnesota courts are not authorized to exercise such a broad power of review over the Minnesota Legislature. See ante, at 471, n. 15. After rejecting the trial court's findings, the Court goes on to find that any burden the Minnesota statute may impose upon interstate commerce is not excessive in light of the substantial state interests furthered by the statute. Ante, at 473. However, the Minnesota Supreme Court expressly found that the statute is not rationally related to the substantial state interests identified by the majority.14 Because I believe, as explained in Part I, supra, that the Court’s intrusion upon the lawmaking process of the State of Minnesota is without constitutional sanction or precedential support, it is clear to me that the findings of the Minnesota Supreme Court must be respected by this Court. Accordingly, the essential predicate for the majority’s conclusion that the “local benefits [are] ample to support Minnesota’s decision under the Commerce Clause,” ante, at 473, is absent.
Ill
The majority properly observes that a state court, when applying the provisions of the Federal Constitution, may not *489apply a constitutional standard more stringent than that announced in the relevant decisions of this Court. See ante, at 461-463, n. 6. It follows from this observation that a state court’s decision invalidating state legislation on federal constitutional grounds may be reversed by this Court if the state court misinterpreted the relevant federal constitutional standard. In this case, however, the Minnesota Supreme Court applied the correct federal equal protection standard and properly declined to consider the Commerce Clause. The majority reverses this decision because it disagrees with the Minnesota courts’ perception of their role in the State’s lawmaking process, not because of any error in the application of federal law. In my opinion, this action is beyond the Court’s authority. I therefore respectfully dissent.
See also ante, at 464, where the Court states that “States are not required to convince the courts of the correctness of their legislative judgments”; and ibid., where the Court states that “litigants may not pro*478cure invalidation of the legislation merely by tendering evidence in court that the legislature was mistaken.”
The majority cites Vance v. Bradley, 440 U S. 93 (1979); Ferguson v. Skrupa, 372 U. S. 726 (1963); Day-Brite Lighting, Inc. v. Missouri, 342 U. S. 421 (1952); United States v. Carolene Products Co., 304 U. S. 144 (1938); and Henderson Co. v. Thompson, 300 U. S. 258 (1937), in support of its conclusion that it is not the function of the Minnesota courts to re-evaluate facts considered by the Minnesota Legislature. See ante, at 464, 469. However, even a cursory examination of these cases reveals that they provide no support for the Court’s decision in this case.
In four of the cited cases, the Court reviewed the actions of lower federal, not state, courts. These cases thus shed no light upon the role a state court properly may play in reviewing actions of the state legislature. In Vance v. Bradley and United States v. Carolene Products, Federal District Courts had invalidated federal statutes on federal constitutional grounds. In both cases, this Court reversed because the District Courts had exceeded the scope of their powers by re-evaluating the factual bases for the congressional enactments. See Vance, supra, at 111-112; Carolene Products, supra, at 152, 154. In Ferguson v. Skrupa, a Federal District Court had invalidated a Kansas statute on federal constitutional grounds. This Court reversed, finding that the District Court had exceeded constitutional limitations by substituting its judgment for that of the Kansas Legislature. See 372 U. S., at 729-731. The Court also indicated in Ferguson that its own power to supervise the actions of state legislatures is narrowly circumscribed. Id., at 730-731. Finally, in Henderson Co. v. Thompson, a Federal District Court had sustained a Texas statute in the face of a constitutional challenge. In affirming that decision, the Court simply observed that "[t]he needs of conservation are to be determined by the Legislature.” 300 U. S., at 264.
In only one of the cases cited by the majority did the Court review a state-court judgment. In Day-Brite Lighting, Inc. v. Missouri, a *479Missouri statute was challenged on due process, equal protection, and Contract Clause theories. The Missouri Supreme Court had upheld the statute, and this Court affirmed. In the course of its opinion, the Court stated that it was not free to re-evaluate the legislative judgment or act as “a superlegislature.” 342 U. S., at 423, 425. The Court did not comment at all upon the extent of the Missouri Supreme Court’s authority to supervise the activities of the Missouri Legislature. Nothing in the Day-Brite Lighting opinion can be construed as the source of the Court’s newly found power to determine for the States which lawmaking powers may be allocated to their courts and which to their legislatures.
Responding to an argument that the lawmaking power of the Virginia Legislature had been improperly assigned to another arm of the State’s government, Justice Cardozo, writing for the Court in Highland Farms Dairy, Inc. v. Agnew, 300 U. S. 608, 612-613 (1937), stated:
“The Constitution of the United States in the circumstances here exhibited has no voice upon the subject. The statute challenged as invalid is one adopted by a state. This removes objections that might be worthy of consideration if we were dealing with an act of Congress. How power shall be distributed by a state among its governmental organs is commonly, if not always, a question for the state itself. Nothing in the distribution here attempted supplies the basis for an exception. The statute is not a denial of a republican form of government. Constitution, Art. IV, § 4. Even if it were, the enforcement of that guarantee, according to the settled doctrine, is for Congress, not the courts. Pacific States Telephone Co. v. Oregon, 223 U. S. 118; Davis v. Hildebrant, 241 U. S. 565; Ohio ex rel. Bryant v. Akron Park District, 281 U. S. 74, 79, 80. Cases such as Panama Refining Co. v. Ryan, 293 U. S. 388, and Schechter Poultry Corp. v. United States, 295 U. S. 495, cited by appellants, are quite beside the point. What was in controversy there was the distribution of power between President and Congress, or between Congress and administrative officers or commissions, a controversy affecting the structure of the nar-*480tional government as established by the provisions of the national constitution.
“So far as the objection to delegation is founded on the Constitution of Virginia, it is answered by a decision of the highest court of the state. In Reynolds v. Milk Commission, 163 Va. 957; 179 S. E. 507, the Supreme Court of Appeals passed upon the validity of the statute now in question. ... A judgment by the highest court of a state as to the meaning and effect of its own constitution is decisive and controlling everywhere.” See also Dreyer v. Illinois, 187 U. S. 71, 83-84 (1902); Sweezy v. New Hampshire, 354 U. S. 234, 256-257 (1957) (Frankfurter, J., concurring in result).
In Ferguson v. Skrupa, supra, the Court indicated that the Federal Constitution does prevent the federal courts from reviewing factual determinations made by a state legislature. In rejecting the substantive due process cases of an earlier era, the Court stated:
“Under the system of government created by our Constitution, it is up to legislatures, not courts, to decide on the wisdom and utility of legislation.” 372 U. S., at 729.
The Court went on to explain this constitutional limitation:
“We have returned to the original constitutional proposition that courts do not substitute their social and economic beliefs for the judgment of legislative bodies, who are elected to pass laws. . . . Legislative bodies have broad scope to experiment with economic problems, and this Court does not sit to ‘subject the State to an intolerable supervision hostile to the basic principles of our Government and wholly beyond the protection which the general clause of the Fourteenth Amendment was intended to secure.’” Id., at 730 (footnote omitted).
The Court’s conclusion in Ferguson that the Constitution imposes limitations upon the power of the federal courts to review legislative judgments was clearly correct and was consistent with the structure of the Federal Constitution and “the system of government created” therein. The Constitution defines the relationship among the coordinate branches of the Federal Government and prescribes for each branch certain limited powers. The Federal Constitution, however, is silent with respect to the powers of the coordinate branches of state governments and the relationship among those branches.
Although this proposition is so well established as to require no citation of authority, abundant authority is readily available. See, e. g., North Carolina v. Butler, 441 U. S. 369, 376, n. 7 (1979); Ward v. Illinois, 431 U. S. 767, 772 (1977); Eastlake v. Forest City Enterprises, Inc., 426 U. S. 668, 674, n. 9 (1976); Hortonville Joint School District No. 1 v. Hortonville Education Assn., 426 U. S. 482, 488 (1976); Mullaney v. Wilbur, 421 U. S. 684, 691 (1975); Memorial Hospital v. Maricopa County, 415 U. S. 250, 256 (1974); Wardius v. Oregon, 412 U. S. 470, 477 (1973); Groppi v. Wisconsin, 400 U. S. 505, 507 (1971).
In its memorandum in this case, the state trial court initially observed that it was not free to “substitute its judgment for that of the legislature as to the wisdom or desirability of the act.” App. A-24. With respect to the facts considered by the legislature, however, the trial court found that “as fact-finder, [it was] obliged to weigh and evaluate this evidence, much of which was in sharp conflict.” Id., at A-25.
In its opinion affirming the trial court’s decision, the Minnesota Supreme Court took a similar view of the function to be performed by the Minnesota courts when reviewing Minnesota legislation:
“We are aware of the deference that is accorded to the legislature when the present type of statute is analyzed on equal protection grounds. Nevertheless, our inquiry into the constitutional propriety of the present *482classification separating paper containers from plastic nonrefillables is dependent upon facts. Based upon the relevant findings of fact by the trial court, supported by the record, and upon our own independent review of documentary sources, we believe the evidence conclusively demonstrates that the discrimination against plastic nonrefillables is not rationally related to the Act’s objectives.” 289 N. W. 2d 79, 82 (1979).
In its footnote 6, ante, at 461-463, the Court takes issue with my suggestion that its action in this case is unprecedented by citing four eases in which the Court reversed State Supreme Court decisions invalidating provisions of state law on federal equal protection grounds. See Idaho Dept. of Employment v. Smith, 434 U. S. 100 (1977) (per curiam); Arlington County Board v. Richards, 434 U. S. 5 (1977) (per curiam); Richardson v. Ramirez, 418 U. S. 24 (1974); Lehnhausen v. Lake Shore Auto Parts, 410 U. S. 356 (1973). In each of those cases, however, this Court concluded that the state court had applied an incorrect legal standard; in none did this Court reassess the factual predicate for the state-court decision.
In Idaho Dept. of Employment, the Idaho Supreme Court had invalidated a statutory classification, not because it generally failed to further legitimate state goals, but rather because the court had found that the classification was imperfect since some members of the class denied *483unemployment benefits were in fact as available for full-time employment as members of the class entitled to benefits under the Idaho statute. See Smith v. Department of Employment, 98 Idaho 43, 43-44, 557 P. 2d 637, 637-638 (1976), citing Kerr v. Department of Employment, 97 Idaho 385, 545 P. 2d 473 (1976). This Court did not disagree with the Idaho court’s finding that the classification was imperfect, but merely held that this imperfection was legally insufficient to invalidate the statute under the Equal Protection Clause. 434 U. S., at 101-102. In Arlington County Board v. Richards, the Virginia Supreme Court had recognized the rational-basis test as the appropriate equal protection standard, but then had proceeded to apply a more stringent standard to the municipal ordinance at issue. The court had expressly noted that the municipal ordinance “may relieve the [parking] problems” to which it was directed. However, the court concluded that the means employed by the county to deal with these problems — a classification based upon residency — created an unconstitutional “invidious discrimination.” See Arlington County Board v. Richards, 217 Va. 645, 651, 231 S. E. 2d 231, 235 (1977). This Court reversed, rejecting the conclusion that the ordinance’s residency classification resulted in an invidious discrimination.' 434 U. S., at 7. In Richardson v. Ramirez, a voting rights case, the California Supreme Court was reversed, not because it had re-examined the factual determinations of the California Legislature, but because this Court found that the statutory discrimination at issue was expressly authorized by § 2 of the Fourteenth Amendment. 418 U. S., at 41-56. Finally, in Lake Shore Auto Parts v. Lehnhausen, the Illinois Supreme Court had held, in essence, that a classification used in determining liability for a property tax must, as a constitutional matter, be based upon the nature of the property at issue, and not upon the corporate or noncorporate character of the property’s owner See Lake Shore Auto Parts v. Korzen, 49 Ill. 2d 137, 149-151, 273 N. E. 2d 592, 598-599 (1971) This Court rejected this principle, finding it inconsistent with prior decisions clearly establishing that distinctions between individuals and corporations in tax legislation violated no constitutional rights. 410 U. S., at 359-365.
As the majority observes, the Court in each of these cases reversed the state-court decisions because the state courts had applied an equal protection standard more stringent than that sanctioned by this Court. Quite frankly, in my opinion it would have been sound judicial policy *484in all four of those cases to allow the state courts to accord even greater protection within their respective jurisdictions than the Federal Constitution commands. See my dissent in Idaho Dept. of Employment, supra, at 104. But what is especially relevant here is the fact that in none of those cases had the state courts found, after a full evidentiary hearing, that the factual predicate for the state law at issue was simply not true. The Minnesota courts in this case made such a finding after the development of an extensive record. The Minnesota courts then applied the correct federal legal standard to the facts revealed by this record and concluded that the statutory classification was not rationally related to a legitimate state purpose. As I read the cases cited by the majority, they are simply inapposite in this case. My own research has uncovered no instance in which the Court has reversed the decision of the highest court of a. State, as it does in this case, because the state court exceeded some federal constitutional limitation upon its power to review the factual determinations of the state legislature. The Court has never before, to my knowledge, undertaken to define, as a matter of federal law, the appropriate relationship between a state court and a state legislature.
In most of the cases in which the Court has indicated that courts may not substitute their judgment for that of the legislature, the Court was reviewing decisions of the lower federal courts. See, e. g., New Orleans v. Dukes, 427 U. S. 297, 303 (1976) (per curiam); Hughes v. Alexandria Scrap Corp., 426 U. S. 794, 812 (1976); United States v. Maryland Savings-Share Ins. Corp., 400 U. S. 4, 6 (1970) (per curiam); Firemen v. Chicago, R. I. & P. R. Co., 393 U. S. 129, 136, 138-139 (1968); Williamson v. Lee Optical Co., 348 U. S. 483, 487-488 (1955); Secretary of Agriculture v. Central Roig Refining Co., 338 U. S. 604, 618-619 (1950); Daniel v. Family Insurance Co., 336 U. S 220, 224 (1949); Clark v. Paul Gray, Inc., 306 U. S. 583, 594 (1939); South Carolina State Highway Dept. v. Barnwell Bros., Inc., 303 U. S. 177, 190-191 (1938); Bay side Fish Flour Co. v. Gentry, 297 U. S. 422, 427-428, 430 (1936); Borden’s Farm Products Co. v. Ten Eyck, 297 U. S. 251, 263 (1936); Sproles v. Binford, 286 U. S. 374, 388-389 (1932); Standard Oil Co. v. Marysville, 279 U. S. 582, 584, 586 (1929); Hebe Co. v. Shaw, 248 U. S. 297, 303 (1919). In those instances in which the Court was reviewing state-court decisions, its statements with respect to the limited role of the judiciary in reviewing state *485legislation clearly concerned its own authority to act as a “superlegisla-ture,” not the authority of a state court to do so where permitted by state law. See, e. g., Exxon Corp. v. Governor of Maryland, 437 U. S. 117, 124 (1978); Railway Express Agency, Inc. v. New York, 336 U. S. 106, 109 (1949); Olsen v. Nebraska, 313 U. S. 236, 246 (1941); Zahn v. Board of Public Works, 274 U. S. 325, 328 (1927); Cusack Co. v. Chicago, 242 U. S. 526, 531 (1917); Hadacheck v. Los Angeles, 239 U. S 394, 413-414 (1915); Price v. Illinois, 238 U. S. 446, 452-453 (1915); Laurel Hill Cemetery v. San Francisco, 216 U. S. 358, 365 (1910).
This Court will defer to the interpretation of state law announced by the highest court of a State even where a more reasonable interpretation is apparent, see, e. g., O’Brien v. Skinner, 414 U. S. 524, 531 (1974), a contrary construction might save a state statute from constitutional invalidity, see, e. g., Landmark Communications, Inc. v. Virginia, 435 U. S. 829, 837, n. 9 (1978), or it appears that the state court has attributed an unusually inflexible command to its legislature, see, e. g., Kingsley Pictures Corp. v Regents, 360 U. S. 684, 688-689 (1959).
As the majority notes, the evidence considered by the Minnesota courts was conflicting, ante, at 460, 464, 469, and the respondents “produced impressive supporting evidence at trial” indicating that the decision of the Minnesota Legislature was factually unsound. Ante, at 463. In light of this record, this Court clearly cannot reverse the concurrent factual findings of two state courts.
Moreover, since there is no significant difference between plastic containers and paper containers in terms of environmental impact, and since no one contends that the Minnesota statute will reduce the consumption of dairy products, it is not difficult to understand the state judges’ skeptical scrutiny of a legislative ban on the use of one kind of container without imposing any present or future restriction whatsoever on the use of the other.
It is true that the Court carefully avoids an express acknowledgment that the Minnesota Supreme Court applied the correct legal standard. Not one word in the Court’s opinion, however, suggests that the Court has any disagreement with the state court’s understanding of the proper federal rule.
The trial court made the following findings of fact:
“12. Despite the purported policy statement published by the Legislature as its basis for enacting Chapter 268, the actual basis 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.
“23. Despite the purported policy reasons published by the Legislature as bases for enacting Chapter 268, actual bases were to isolate from interstate competition the interests of certain segments of the local dairy and pulpwood industries. The economic welfare of such local interests can be *487promoted without the remedies prescribed in Chapter 268.” App. A-19, A-22.
These findings were repeated in the memorandum filed by the trial court in this case:
“The relevant legislative history of Chapter 268 support [sic] a conclusion that the real basis for it was to serve certain economic interests (paper, pulpwood, and some dairies) at the expense of other competing economic groups (plastic and certain dairies) by prohibiting the plastic milk bottle.” Id., at A-24.
According to the majority, its decision to address the Commerce Clause question is justified “because of the obvious factual connection between the rationality analysis under the Equal Protection Clause and the balancing of interests under the Commerce Clause.” Ante, at 470, n. 14. The majority cites New York City Transit Authority v. Beazer, 440 U. S. 568 (1979), in support of this rationale. This justification is inadequate, in my opinion, for two reasons.
First, in light of the trial court’s factual finding that the Minnesota Legislature enacted the statute for protectionist, rather than environmental, reasons, see n. 12, supra, the Equal Protection Clause and Commerce Clause inquiries are not necessarily as similar as the Court suggests. As the majority acknowledges, if a state law which purports to promote environmental goals is actually protectionist in design, a virtually automatic rule of invalidity, not a balancing-of-interests test, is applied. See ante, at 471. See also New Orleans v. Dukes, 427 U. S., at 304, n. 5.
Second, in Beazer the Court reviewed the decision of a lower federal court, not a state supreme court. While this Court, in its discretion, may elect to deprive lower federal courts of the opportunity to decide particular statutory questions, it seems to me that respect for the Minnesota Supreme Court as the highest court of a sovereign State dictates that we not casually divest it of authority to decide a constitutional question on which it properly declined to comment when this case was first before it. Such deference is especially appropriate here because the Court’s analysis of *488the Commerce Clause issue requires rejection of the state trial court's findings of fact.
As noted in Part I, supra, the Court rejects the Minnesota Supreme Court’s findings, not because they are without support in the record— they clearly are adequately supported, see n. 10, supra — but because it feels that the Minnesota Supreme Court was without authority to do anything other than endorse the factual conclusions of the Minnesota Legislature.