I concur in the majority’s result, which reverses the Court of Appeals decision and reinstates the defendant’s conviction. I also agree with the lead opinion’s rejection of the defendant’s constitutional argument. I write separately because the lead opinion’s interpretation of MCL 333.7531; MSA 14.15(7531) ignores the plain meaning of the statute. Contrary to its assurances that only the constitutionality of this particular conviction is being addressed, by refusing to recognize *310that the statute shifts the burdens of production and persuasion onto the defendant, the lead opinion would alter the burden of proof established by the statute. If, as the lead opinion would hold, the burden of production, once met, shifts back to the prosecution, its interpretation effectively would read out of the statute the words "[t]he burden of proof of an exemption or exception is upon the person claiming it.” MCL 333.7531(1); MSA 14.15(7531)(1). The lead opinion’s justification appears to be the failure of the parties to correctly interpret the statute. However, a litigant’s mistake does not alter this Court’s obligation to uphold legislative enactments that meet constitutional muster. I would hold that § 7531 constitutionally places "[t]he burden of proof” both of production and persuasion, on a defendant claiming an exemption under the statute.
This opinion is divided into three sections. In the first, I address the lead opinion’s failure to justify its adoption of an interpretation of § 7531 directly at odds with the plain language of the act. In the second part of the opinion, I explain why the statute is not constitutionally defective. In the third section, I attempt to explain how the regulatory nature of § 7531 makes rebutting the exemption extremely difficult when compared to more traditional affirmative defenses.
i
Section 7531 squarely places the burden of proving the existence of a prescription on the defendant:
(1) It is not necessary for this state to negate *311any exemption or exception in this article in a complaint, information, indictment, or other pleading or in a trial, hearing, or other proceeding under this article. The burden of proof of an exemption or exception is upon the person claiming it.
(2) In the absence of proof that a person is the authorized holder of an appropriate license or order form issued under this article, the person is presumed not to be the holder of the license or order form. The burden of proof is upon the person to rebut the presumption. [MCL 333.7531; MSA 14.15(7531). Emphasis added.]
In other words, it is incumbent on a defendant charged with an offense regarding a substance that may be lawfully possessed pursuant to a license or order form to prove that such possession is authorized by the existence of such permission. This language on its face applies only to those substances that the state has not chosen to regulate by criminalizing all possession. Thus, possession of prescription drugs, unlike other controlled substances such as heroin, is subject to criminal penalty only when it is not authorized by a prescription. In obvious recognition of "the insurmountable task of producing evidence to prove lack of a prescription,” ante at 295, the Legislature has placed both the burden of production and the burden of proving the exemption on the person claiming it.
The lead opinion does not persuasively contest this reading of § 7531,1 nor could it; "when legislative intent is clearly revealed in an unambiguous statute, the plain language of the statute must be enforced.” Kammer Asphalt Paving Co v East China Twp Schools, 443 Mich 176, 183; 504 NW2d *312635 (1993).2 Rather, the lead opinion relies primarily on the failure of the parties to argue this interpretation of the statute to explain the failure to apply § 7531 as written.
The lead opinion states that because "the trial court and the parties have interpreted § 7531 as involving the burden of production” ante at 289, n 10 (emphasis in original), the lead opinion would limit its "holding to the constitutionality of § 7531 as it was applied in this case.” Ante at 292, n 13. If the lead opinion had merely reinstated the defendant’s conviction pursuant to § 7531, the need to fully interpret the statute may have been avoided, although such a resolution would have been of limited value to the bench and bar. However, in the present case, the lead opinion also would set an evidentiary threshold to be met in future cases, see part hi, pp 294-300. By doing so, the lead opinion endorses an interpretation of § 7531 that would in future cases shift only the burden of production to the defendant, thus requiring the prosecution to face the task of proving lack of a prescription beyond a reasonable doubt. Despite its assurances, the lead opinion has not left "for another day the question whether . . . Michigan” allows the shifting of the burden of persuasion on the defendant. Ante at 292, n 13.
The lead opinion would achieve the right result at the cost of weighing this defendant’s direct testimony against that of a more credible defendant’s assertion. Such balancing is usually inappropriate when a defendant presents direct evidence in support of an affirmative defense. Professor McCormick notes that while the amount of *313evidence necessary to shift the burden of production to the prosecution in circumstantial evidence cases is often controversial,
[generally no difficulty occurs where the evidence is direct. Except in rare cases, it is sufficient, though given by one witness only, however negligible a human being she may be. [2 McCormick, Evidence (4th ed), § 338, p 434.]
The defendant in the present case testified in his own behalf. That testimony certainly should have been enough to shift the burden to the prosecutor if this statute placed only the burden of production on the defendant.
The lead opinion’s creation of an evidentiary threshold for the defendant implicitly acknowledges the problem of requiring the prosecutor to "rebut the claim . . . [by contacting] the thousands of practicing physicians to prove the negative, that each had not prescribed the drugs to the defendant.” Ante at 295. However, the remedy for that quandary is not to create an evidentiary threshold based on an appellate court’s evaluation of the sufficiency of a given defendant’s testimony. Such an approach invades the factfinder’s province, invites abuse by trial courts, and leaves the prosecution’s predicament intact. The appropriate remedy is the one selected by the Legislature, which in the plain language of the statute has placed the burden of proof and production on the defendant.
In this context, I cannot agree with the decision to defer to the interpretation of § 7531 advanced by the trial judge and the parties. As Justice Voelker once observed in typically puckish fashion, "[i]t is of course elementary that litigants cannot bind us by their interpretation of a statute, however wrong and however much their interpretation, if they persuaded us to follow it, might help *314them lose their case.”3 State Highway Comm’r v Simmons, 353 Mich 432, 438; 91 NW2d 819 (1958). In the present case, the only conceivable reason for not interpreting the statute as written would be if it unconstitutionally shifted the burden of proof to the defendant. It is to the constitutional question that I now turn.
ii
The lead opinion does not explain how it is unconstitutional to place the burden of persuasion on the defendant. In fact, the rejection by the lead opinion of the defendant’s constitutional argument is so broad that it would seem to allow the application of the statute as written:
The language concerning a prescription or other authorization refers to an exemption rather than an element of the crime. Because § 7531 requires defendant to bear the burden of proof regarding presence of a prescription, and that fact is not determinative of an essential element of the crime of possession of Valium and Xanax, § 7531 is not violative of due process. [Ante at'292-293.]
As the lead opinion recognizes, the controlling United States Supreme Court decision, Patterson v New York, 432 US 197; 97 S Ct 2319; 53 L Ed 2d 281 (1977), 4 requires no more of a statute. Other authority from the federal courts bears this out.
*315In Woods v Butler, 847 F2d 1163 (CA 5, 1988), cert den 488 US 970 (1988), the United States Court of Appeals was faced with a claim for habeas corpus relief in a case presenting an issue nearly identical to that in the present controversy. The relevant state statute provides:
It shall not be necessary for the state to negate any exemption or exception set forth in this part in any complaint, information, indictment or other pleading or in any trial, hearing, or other proceeding under this part, and the burden of proof of any such exemption or exception shall be upon the person claiming its benefit. [La Rev Stat 40:990A.]
The defendant, convicted of possession of a controlled substance, phenmetrazine, argued that the state statute impermissibly shifts the burden of proof of an element of the crime onto the defendant in violation of the Due Process Clause of the United States Constitution._
*316The court rejected the defendant’s argument and affirmed the conviction:
Balancing the interests of the state in the effective and efficient administration of justice with a defendant’s right that the state prove the existence beyond a reasonable doubt of each element of a crime before conviction, the Supreme Court has concluded that, a state may permissibly place (1) the burden of going forward with evidence and (2) the burden of persuasion by a preponderance of the evidence as to an affirmative defense on the accused. Martin v Ohio, 480 US 228; 107 S Ct 1098; 94 L Ed 2d 267 (1987); see also Simopoulos v Virginia, 462 US 506; 103 S Ct 2532; 76 L Ed 2d 755 (1983); Patterson v New York [supra]. [Woods at 1165.]
The court continued by explaining some of the common-sense reasons for the burden shift:
An individual accused of possession of a controlled dangerous substance who claims to have a valid prescription authorizing the possession of the drugs is in the best position to possess knowledge of the facts necessary to prove the defense—the prescribing doctor, the reason for the prescription, and the location from which the controlled substance was obtained. Further, it cannot be disputed that Louisiana may constitutionally criminalize and punish the act of possessing a controlled dangerous substance. [Id. at 1166.]
Finally, the court also recognized the constitutionality of the legislature’s shift of the burden of persuasion, not just of production, as in the comparable federal statute:
In comparing the provisions of the federal Controlled Substances Act with the similar provisions in the lcdsl [Louisiana Controlled Dangerous Substance Act], we are mindful that while Louisiana *317places the burden of persuasion of an exception on the defendant, the federal statute requires only that the defendant come forward with evidence of the exception. In this regard, the government retains the ultimate burden of persuasion on the exception under the federal act. However, because the Supreme Court has concluded that a state may properly place not only the burden of going forward with evidence of a defense on the accused, but also the burden of persuasion of that defense on the accused, the fact that the Louisiana act requires more of the defendant than the federal act does not render the lcdsl constitutionally infirm. [Id. at 1167.]
Woods is instructive not only because it declares that the shift of the burden of persuasion is constitutional, but also because it recognizes that not all legislative schemes dealing with the burden of proof are alike, nor need they be. As Patterson made clear,5 as long as the statute does not violate the constitution by placing on the defendant the burden of persuasion to negate an element of the crime, the states are free to define crimes, exemptions, and defenses as they will.
The lead opinion states that "[t]he statute here is analogous to the concealed weapon statute interpreted by this Court in People v Henderson, 391 Mich 612; 218 NW2d 2 (1974).” Ante at 290. However, as comparisons of the statute indicate, the analogy is not convincing. MCL 776.20; MSA 28.1274(1) provides in pertinent part:_
*318In any prosecution for the violation of any acts of the state relative to use, licensing and possession of pistols or firearms, the burden of establishing any exception, excuse, proviso or exemption contained in any such act shall be upon the defendant but does not shift the burden of proof for the violation.
Unlike the language in § 7531, which relieves the state of the burden of negating an exemption, and places the burden of proof of an exemption on the person claiming it, the concealed weapons statute arguably states that the burden of proof "for the violation” does not shift.
Moreover, the significance of the comparison is questionable. As the lead opinion notes, Henderson was a pre-Patterson case, ante at 292, n 13, a fact that may have colored the Henderson Court’s view of its ability to interpret the statute to place the burden of persuasion on the defendant. In any event, Henderson’s interpretation of a differently worded statute does not justify a construction of § 7531 that effectively redacts the directive that "[t]he burden of proof of an exemption or exception is upon the person claiming it.”6
hi
The approach of the lead opinion may reflect an unarticulated concern for the consequences of creating affirmative defenses that shift the burdens of production and persuasion. To the extent that it can be assumed that this is the concern, it should be clearly understood that the section in question only creates an exemption to a regulatory measure, and as such does not implicate the concerns *319raised by statutes that shift the burdens of production and persuasion of more traditional affirmative defenses.
McCormick observes that "[t]he term affirmative defense is traditionally used to describe the allocation of a burden, either of production or persuasion, or both, to the defendant in a criminal case.” Evidence, supra, § 347, p 480. The same may be said of an "exemption.” The difference is not in where the burden of persuasion lies,7 but in the regulatory character of the exemption. By contrast with more traditional crimes where an affirmative defense in effect concedes the facial criminality of the conduct and presents a claim of justification or excuse, an exemption to a regulatory scheme asserts that the defendant’s conduct was outside the reach of the particular regulation.
With a conventional affirmative defense, for example, some fact if proved, will completely or partially excuse the conduct of the accused. Thus, self-defense will completely excuse the crime of murder. Two things can be drawn from the murder example. First, the conduct of the accused is inherently wrongful, and thus socially condemned unless it occurs under circumstances indicating *320excuse or justification. The second, a closely related and not so obvious aspect of the self-defense example is that it is not unfairly difficult to disprove. In a state that places only the burden of production on the defendant, leaving the prosecutor with the burden of proving that the defendant did not act in self-defense, the prosecutor is faced with a burden that will vary appropriately with the case. Because murder is presumed wrongful, and because the level of evidence that the prosecutor will need to meet the burden of proof beyond a reasonable doubt is proportional to the level of proof introduced by the accused, the question whether the people will prevail will depend largely on the strength of the defendant’s evidence. Such a system rationally measures the truth. The defendant who produces more evidence of self-defense causes the prosecutor’s burden on rebuttal to rise. The defendant who introduces only slight evidence raises the prosecutor’s burden only slightly.
Regulatory schemes, on the other hand, often involve conduct that is not on its face wrongful. The controlled substances statute, MCL 333.7101 et seq.; MSA 14.15(7101) et seq., is a mixed scheme covering a range of behavior that spans the obviously illegal, as with possessing and delivering most schedule one substances,8 to the presumptively legal, such as the possession of many of the drugs available by prescription. In cases involving presumably illegal behavior, like possessing heroin, the circumstances are more akin to the traditional affirmative defense. In defense of possession of heroin, where the burden of proof rests on the prosecution to show knowledge, the prosecution *321faces the same situation it faces with self-defense: the conduct is presumed wrongful, and the level of evidence that the prosecutor will need to meet the burden of proof of knowledge beyond a reasonable doubt is proportional to the level of proof introduced by the accused. The question whether the people have proven knowledgeable possession thus depends largely on the strength of the defendant’s evidence.
The situation is far different further down the regulatory ladder. In cases such as the present one, the conduct is not obviously wrongful. It is regulated because the state has determined that it must be for the health and welfare of Michigan’s citizens. But regulation in the case of schedule four substances, MCL 333.7218; MSA 14.15(7218), means an individual has a privilege by license or other means to possess certain drugs. A prescription is relatively easily obtained from a doctor and filled at a local pharmacy, and the fact that one has been obtained is information naturally possessed by the person obtaining it. The prosecutor, who must disprove the exemption, the prescription, is faced with the difficult burden9 of proving a negative without the reasonable means to do so. Unlike the case of presumed wrongful conduct, where the prosecutor’s burden is proportional to the defendant’s proofs, in cases involving conduct only made illegal by regulation, a simple assertion by the defendant that his possession is by prescription increases the prosecutor’s burden of proof to the point that a conscientious jury may be obligated to find that the government had not shown guilt beyond a reasonable doubt. This increase in the prosecutor’s burden is not rationally tied to *322the truth, but to the method of regulating the activity.
The Legislature understood how difficult it would be for a prosecutor to rebut a defendant’s simple assertion in a case such as the present one. It also understood how difficult it would be to regulate the activity employing such an approach. That presumably is why the Legislature placed the burdens of production and persuasion on the defendant. It will be a rare individual legally in possession of a controlled substance who will not be able to show a prescription, remember the name of a doctor, or remember the name of a pharmacist.
While cases such as Patterson leave no doubt that the Due Process Clause of the federal constitution permits the state to allocate the burdens as it has done in this case, it must be clearly understood that for the uncertain period between In re Winship, 397 US 358; 90 S Ct 1068; 25 L Ed 2d 368 (1970), and Patterson, the traditional affirmative defense, which involved mitigation or justification of concededly criminal conduct, shifted only the burden of production to the defense. The traditional exemption, by contrast, involves activity that is unlawful only when engaged in without compliance with regulatory restraints, such as licensure, reporting, or other governmental authorization.
Self-defense is a true affirmative defense because at common law all homicide was murder. The possession of weapons, the receipt of money, the possession of prescription drugs, and a host of other activity is criminally proscribed only when it is engaged in without the authorization the government deems necessary for its control. Such statutes are directed to compliance with regulations deemed necessary to control otherwise lawful *323activity.10 In these situations, when the burden of proving noncompliance undermines the regulatory scheme, the Legislature may opt to transfer the burdens both of production and persuasion to the individual who claims his conduct is lawful because it falls into an exemption to the regulations imposed on his activity.
Thus properly understood, applying the exemption or exception provision of § 7531 as written bodes no ill jurisprudential consequences for other portions of this statute or other "true” affirmative defenses. The state has not sought to make unknowing possession of a controlled substance an offense by placing the burden on a defendant to show he did not know that what he possessed was a controlled substance.
CONCLUSION
Section 7531 is an obvious and constitutional statute. The lead opinion does not forcefully argue otherwise. Rather, when all is said and done, the only justification by the lead opinion for its decision to ignore the language of this obvious and constitutional piece of legislation is a misunderstanding of the statute. Because I believe that the Court’s analysis is dictated by the plain language of a constitutional statute, I would hold § 7531 places the burdens of production and persuasion on the defendant. 11 The fact that it was not so *324placed in the present case was to the defendant’s benefit. I concur in affirming the conviction and reversing the decision of the Court of Appeals.
Riley and Griffin, JJ., concurred with Boyle, J.Ante at 282-283.
See also Achtenberg v East Lansing, 421 Mich 765, 770; 364 NW2d 277 (1985), in which Justice Cavanagh, writing for a unanimous Court, noted: "When the language of a statute is clear, courts must apply it as written.”
See also Detroit v Beckman, 34 Mich 125, 126 (1876) (opinion of Cooley, J.), "the admission of a rule of law could not obligate the court to accept and act upon it.”
The United States Supreme Court reaffirmed Patterson in Martin v Ohio, 480 US 228, 232-234; 107 S Ct 1098; 94 L Ed 2d 267 (1987), observing:
[In Patterson] [w]e . . . emphasized the preeminent role of the States in preventing and dealing with crime and the reluctance of the Court to disturb a State’s decision with respect to the definition of criminal conduct and the procedures *315by which the criminal laws are to be enforced in the courts, including the burden of producing evidence and allocating the burden of persuasion.
It would be quite different if the jury had been instructed that self-defense evidence could not be considered in determining whether there was a reasonable doubt about the State’s case, i.e., that self-defense evidence must be put aside for all purposes unless it satisfied the preponderance standard. Such an instruction would relieve the State of its burden and plainly run afoul of Winship’s mandate. 397 US [358] 364 [90 S Ct 1068; 25 L Ed 2d 368 (1970)]. The instructions in this case could be clearer in this respect, but when read as a whole, we think they are adequate to convey to the jury that all of the evidence, including the evidence going to self-defense, must be considered in deciding whether there was a reasonable doubt about the sufficiency of the State’s proof of the elements of the crime.
The United States Supreme Court has continued to cite Patterson and Martin with approval. Walton v Arizona, 497 US 639, 650; 110 S Ct 3047; 111 L Ed 2d 511 (1990); Schad v Arizona, 501 US 624, 639-640; 111 S Ct 2491; 115 L Ed 2d 555 (1991); Gilmore v Taylor, 508 US —, —; 113 S Ct 2112, 2117; 124 L Ed 2d 306 (1993).
McCormick, commenting on Patterson, observed:
The court in Patterson decided the constitutionality of the . allocation of the burden of proof by a formalistic analysis of state law: due process was not violated because the defendant did not have the burden of proof on any fact that state law had identified as an element of the offense. [Evidence (4th ed), § 347, p 483.]
The same defects exist in People v Dempster, 396 Mich 700; 242 NW2d 381 (1976), which relies heavily on Henderson and was also decided before Patterson.
But see People v Smith, 71 Ill 2d 95, 105; 374 NE2d 472 (1978). The Supreme Court of Illinois, interpreting the criminal code of Illinois, defined an affirmative defense to shift only the burden of production onto the defendant, while an exemption placed both the burdens of production and persuasion onto the person claiming it. The court explained:
The legislature has added to the unlawful use of weapons statute a long litany of exemptions. Ten separately enumerated exempt categories apply .... For the State to be saddled with negating each defendant’s place . . . would place impossible burdens upon the effective prosecution of this type of case. The legislature has avoided this problem by requiring the prosecution to prove each and every element of the offense beyond a reasonable doubt and by requiring the defendant to prove his entitlement to the exemption.
Schedule one substances, MCL 333.7211; MSA 14.15(7211), have no "accepted medical use in treatment in the United States or lack[] accepted safety for use in treatment under medical supervision.” ,
If disproving the exemption was an element of the offense, it would be a nearly impossible burden.
Nothing in this opinion is meant to suggest that the Legislature could not constitutionally place the burden of persuasion on the defendant in cases involving traditional affirmative defenses. It is clear from Martin v Ohio, supra, that such burden shifting is permitted. Bather, the comparison between regulatory and traditional affirmative defenses is meant to illustrate the common-sense reasons why our Legislature chose to place both the burden of production and provision on the defendant.
We leave for another day the question what standard of proof must be presented by a defendant to meet the burden of persuasion under § 7531. See Martin, supra.