This case presents constitutional questions arising out of the conviction of the petitioner, Dr. Timothy Leary, for violation of two federal statutes governing traffic in marihuana.

The circumstances surrounding petitioner's conviction were as follows. On December 20, 1965, petitioner left New York by automobile, intending a vacation trip to Yucatan, Mexico. He was accompanied by his daughter and son, both teenagers, and two other persons. On December 22, 1965, the party drove across the International Bridge between the United States and Mexico at Laredo, Texas. They stopped at the Mexican customs station and, after apparently being denied entry, drove back across the bridge. They halted at the American secondary inspection area, explained the situation to a customs inspector, and stated that they had nothing from Mexico to declare. The inspector asked them to alight, examined the interior of the car, and saw what appeared to be marihuana seeds on the floor. The inspector then received permission to search the car and passengers. Small amounts of marihuana were found on the car floor and in the glove compartment. A personal search of petitioner's daughter revealed a silver snuff box containing semirefined marihuana and three partially smoked marihuana cigarettes.

Petitioner was indicted and tried before a jury in the Federal District for the Southern District of Texas, on three counts. First, it was alleged that he had knowingly smuggled marihuana into the United States, in violation of 21 U.S.C. § 176a.1 Second, it was charged that he had knowingly transported and facilitated the transportation and concealment of marihuana which had been illegally imported or brought into the United States, with knowledge that it had been illegally imported or brought in, all again in violation of § 176a.2 Third, it was alleged that petitioner was a transferee of marihuana and had knowingly transported, concealed, and facilitated the transportation and concealment of marihuana without having paid the transfer tax imposed by the Marihuana Tax Act, 26 U.S.C. § 4741 et seq., thereby violating 26 U.S.C. § 4744(a)(2).3

After both sides had presented their evidence and the defense had moved for a judgment of acquittal, the District Court dismissed the first or smuggling count.4 The jury found petitioner guilty on the other two counts. He was tentatively sentenced to the maximum punishment, pending completion of a study and recommendations to be used by the District Court in fixing his final sentence.5 On appeal, the Court of Appeals for the Fifth Circuit affirmed. 383 F.2d 851 (1967). That court subsequently denied a petition for rehearing and rehearing en banc. 392 F.2d 220 (1968).

We granted certiorari, 392 U.S. 903, 88 S.Ct. 2058, 20 L.Ed.2d 1362 (1968), to consider two questions: (1) whether petitioner's conviction for failing to comply with the transfer tax provisions of the Marihuana Tax Act violated his Fifth Amendment privilege against self-incrimination; (2) whether petitioner was denied due process by the application of the part of 21 U.S.C. § 176a which provides that a defendant's possession of marihuana shall be deemed sufficient evidence that the marihuana was illegally imported or brought into the United States, and that the defendant knew of the illegal importation or bringing in, unless the defendant explains his possession to the satisfaction of the jury. For reasons which follow, we hold in favor of the petitioner on bt h issues and reverse the judgment of the Court of Appeals.

We consider first petitioner's claim that his conviction under the Marihuana Tax Act violated his privilege against self-incrimination.

Petitioner argues that reversal of his Marihuana Tax Act conviction is required by our decisions of last Term in Marchetti v. United States, 390 U.S. 39, 88 S.Ct. 697, 19 L.Ed.2d. 889 (1969); Grosso v. United States, 390 U.S. 62, 88 S.Ct. 709, 19 L.Ed.2d 906 (1968), and Haynes v. United States, 390 U.S. 85, 88 S.Ct. 722, 19 L.Ed.2d 923 (1968). In Marchetti, we held that a plea of the Fifth Amendment privilege provided a complete defense to a prosecution for failure to register and pay the occupational tax on wagers, as required by 26 U.S.C. §§ 4411—4412. We noted that wagering was a crime in almost every State, and that 26 U.S.C. § 6107 required that lists of wagering taxpayers be furnished to state and local prosecutors on demand. We concluded that compliance with the statute would have subjected petitioner to a "real and appreciable"6 risk of self-incrimination. We further recognized that the occupational tax was not imposed in "an essentially non-criminal and regulatory area * * *," 390 U.S., at 57, 88 S.Ct., at 707,7 but was 'directed to a 'selective group inherently suspect of criminal activities."8 We found that it would be inappropriate to impose restrictions on use of the information collected under the statute—a course urged by the Government as a means of removing the impact of the statute upon the privilege against self-incrimination—because of the evident congressional purpose to provide aid to prosecutors. We noted that, unlike the petitioner in Shapiro v. United States, 335 U.S. 1, 68 S.Ct. 1375, 92 L.Ed. 1787 (1948), Marchetti was not required to supply information which had a 'public aspect' or was contained in records of the kind he customarily kept.

In Grosso, we held that the same considerations required that a claim of the privilege be a defense to prosecution under 26 U.S.C. § 4401, which imposes an excise tax on proceeds from wagering. And in Haynes we held for the same reasons that assertion of the Fifth Amendment privilege provided a defense to prosecution for possession of an unregistered weapon under the National Firearms Act, 26 U.S.C. § 5851, despite the fact that in 'uncommon' instances registration under the statute would not be incriminating. See 390 U.S., at 96—97, 99, 88 S.Ct. at 730—731.

In order to understand petitioner's contention that compliance with the Marihuana Tax Act would have obliged him to incriminate himself within the meaning of the foregoing decisions, it is necessary to be familiar with the statutory scheme. The Marihuana Tax Act has tow main subparts. The first imposes a tax on transfers of marihuana, the second an occupational tax upon those who deal in the drug. It is convenient to begin with the occupational tax provisions, 26 U.S.C. §§ 4751—4753.

Section 4751 provides that all persons who 'deal in' marihuana shall be subject to an annual occupational tax. Subsections require that specified categories of persons, such as importers, producers, physicians, researchers, and millers pay varying rates of tax per year. See §§ 4751(1)—(4), (6). Persons who 'deal in' marihuana but do not fall into any of the specified categories are required to pay $3 per year. See § 4751(5). Section 4753 provides that at the time of paying the tax the taxpayer must 'register his name or style and his place or places of business' at the nearest district office of the Internal Revenue Service.

The first of the transfer tax provisions, 26 U.S.C. § 4741, imposes a tax 'upon all transfers of marihuana which are required by section 4742 to be carried out in pursuance of written odder forms.' Section 4741 further provides that on transfers to persons registered under § 4753 the tax is $1 per ounce, while on transfers to persons not so registered the tax is $100 per ounce. The tax is required to be paid by the transferee 'at the time of securing each order form.'9 With certain exceptions not here relevant,10 § 4742 makes it unlawful for any person, 'whether or not required to pay a special tax and register under sections 4751 to 4753,' to transfer marihuana except pursuant to a written order form to be obtained by the transferee. A regulation, 26 CFR § 152.69, provides that the order form must show the name and address of the transferor and transferee; their § 4753 registration numbers, if they are registered; and the quantity of marihuana transferred. Another regulation, 26 CFR § 152.66, requires the transferee to submit an application containing these data in order to obtain the form. Section 4742(d) of the Act requires the Internal Revenue Service to 'preserve' in its records a duplicate copy of each order form which it issues.

Another statutory provision, 26 U.S.C. § 4773, assures that the information contained in the order form will be available to law enforcement officials. That section provides that the duplicate order forms required to be kept by the Internal Revenue Service shall be open to inspection by Treasury personnel and state and local officials charged with enforcement of marihuana laws, and that upon payment of a fee such officials shall be furnished copies of the forms.11

Finally, 26 U.S.C. § 4744(a) makes it unlawful for a transferee required to pay the § 4741(a) transfer tax either to acquire marihuana without having paid the tax or to transport, conceal, or facilitate the transportation or concealment of, any marihuana so acquired.12 Petitioner was convicted under § 4744(a). He conceded at trial that he had not obtained an order form or paid the transfer tax.

If read according to its terms, the Marihuana Tax Act compelled petitioner to expose himself to a 'real and appreciable' risk of self-incrimination, within the meaning of our decisions in Marchetti, Grosso, and Haynes. Sections 4741—4742 required him, in the course of obtaining an order form, to identify himself not only as a transferee of marihuana but as a transferee who had not registered and paid the occupational tax under §§ 4751—4753. Section 4773 directed that this information be conveyed by the Internal Revenue Service to state and local law enforcement officials on request.

Petitioner had ample reason to fear that transmittal to such officials of the fact that he was a recent, unregistered transferee of marihuana 'would surely prove a significant 'link in a chain' of evidence tending to establish his guilt'13 under the state marihuana laws then in effect.14 When petitioner failed to comply with the Act, in late 1965, possession of any quantity of marihuana was apparently a crime in every one of the 50 States, including New York, where petitioner claimed the transfer occurred, and Texas, where he was arrested and convicted.15 It is true that almost all States, including New York and Texas, had exe ptions making lawful, under specified conditions, possession of marihuana by: (1) state-licensed manufacturers and wholesalers; (2) apothecaries; (3) researchers; (4) physicians, dentists, veterinarians, and certain other medical personnel; (5) agents or employees of the foregoing persons or common carriers; (6) persons for whom the durg had been prescribed or to whom it had been given by an authorized medical person; and (7) certain public officials.16 However, individuals in the first four of these classes are among those compelled to register and pay the occupational tax under § 4751—4753;17 in consequence of having registered, they are required to pay only a $1 per ounce transfer tax under § 4741(a)(1). It is extremely unlikely that such persons will remain unregistered, for failure to register renders them liable not only to an additional.$99 per ounce transfer tax but also to severe criminal penalties.18 Persons in the last three classes mentioned above appear to be wholly exempt from the order form and transfer tax requirements.19

Thus, at the time petitioner failed to comply with the Act those persons who might legally possess marihuana under state law were virtually certain either to be registered under § 4753 or to be exempt from the order form requirement. It follows that the class of possessors who were both unrg istered and obliged to obtain an order form constituted a 'selective group inherently suspect of criminal activities.' Since compliance with the transfer tax provisions would have required petitioner unmistakably to identify himself as a member of this 'selective' and 'suspect' group, we can only decide that when read according to their terms these provisions created a 'real and appreciable' hazard of incrimination.

The Government, however, vigorously contends that when the Act is considered together with the accompanying regulations, and in light of existing administrative practice, its incriminatory aspect will be seen to vanish or shrink to less than constitutional proportions. The Government points first to regulations, 26 CFR §§ 152.22, 152.23, added in 1964, which provide that every applicant for registration under §§ 4751—4753 must show that he is legally qualified to deal in marihuana according to the laws of the jurisdiction in which he is operating, and that the district director shall not permit an applicant to register until the director is satisfied that this is true. The Government then cites two other regulations, relating to applications for order forms under § 4742. The first, 26 CFR § 152.67, provides that such applications '(g)enerally * * * shall be signed by the same person or persons signing the application for registration,' but when this is impracticable 'they may be signed by another person, provided a power of attorney authorizing such other person to sign the applications * * * has previously been filed * * *.' The second regulation, 26 CFR § 152.68, states that upon receipt of an application the district director 'shall' compare the signature on the application 'with that appearing on the application for registration or in the power of attorney,' and that '(u)nless the district director is satisfied that the application is authentic it will not be honored.'

The Government asserts that these regulations clearly signify that no person will be permitted to register unless his activities are permissible under the law of his jurisdiction, and that no one will be permitted to obtain an order form and prepay the transfer tax unless he has registered.20 The result, the Government contends, is simply to prohibit nonregistrants like petitioner from dealing in marihuana at all. The Government further asserts that the administrative practice of the Internal Revenue Service and the Bureau of Narcotics has always been consistent with this interpretation, though it concedes that there apparently has never been an attempt by a nonregistrant to prepay the tax. The Government does admit uncertaintly as to whether the fact of such an attempt would have been communicated to law enforcement officials; however, it points out that nothing in the statute or regulations appears to compel such disclosure.21 The Government argues that the regulations and administrative practice effectively refute the existence of a substantial hazard of incrimination at the time petitioner acquired marihuana: first, because a nonregistrant would have known that he could not obtain an order form and consequently never would have applied; second, because there was no substantial risk that an unsuccessful application would have been brought to the attention of law enforcement officials.

We cannot accept the Government's argument, for we find that Congress did intend that a nonregistrant should be able to obtain an order form and prepay the transfer tax. This congrs sional intent appears both from the language of the Act and from its legislative history.

We begin with the words of the statute. Section 4741(a), when read in conjunction with § 4742, imposes a tax upon every transfer of marihuana, with a few exceptions not here relevant.22 Section 4741(a)(1) states that the tax on registrants shall be $1 per ounce and § 4741(a)(2) that the tax on transfers to nonregistrants shall be $100 per ounce. Section 4741(b) states that (s)uch tax shall be paid by the transferee at the time of securing each order form and shall be in addition to the price of such form.' (Emphasis added.) Since § 4741(b) makes no distinction between the § 4741(a)(1) tax on transfers to registrants and the § 4741(a)(2) tax on transfers to nonregistrants, it seems clear that Congress contemplated that nonregistrant as well as registrant transferees should be able to obtain order forms and prepay the tax.

The legislative history also strongly indicates that the Act was intended merely to impose a very high tax on transfers to nonregistrants and not to prohibit such transfers entirely. As a taxing measure, the bill of course originated in the House of Representatives. At the start of the first hearing on the bill, before the House Ways and Means Committee, the committee chairman announced that he had introduced the bill at the request of the Secretary of the Treasury.23 The transfer provisions of the bill then read essentially as they do now.24 The first witness to appear before the Committee was the Treasury Department's Assistant General Counsel, Clinton M. Hester. He began by stating that the bill's purpose was 'not only to raise revenue from the marihuana traffic, but also to discourage the current and widespread undesirable use of marihuana by smokers and drug addicts * * *.'25 He stated that in form the bill was a 'synthesis' of the Harrison Narcotics Act, now 26 U.S.C. § 4701 et seq., and the National Firearms Act, now 26 U.S.C. § 5801 et seq.26 Both of these statutes compelled dealers in the respective goods to register and pay a special tax. Both prohibited transfer except in pursuance of a written form and imposed a transfer tax. However, the transfer provisions differed in that the Narcotics Act provided that no one except a registrant could legally obtain an order form, see 26 U.S.C. § 4705(g), while the Firearms Act merely imposed a $200 tax upon each transfer of a firearm covered by the Act.

The Treasury witness explained that the marihuana tax bill generally followed the plan of the Narcotics Act insofar as it required dealers in marihuana to register and prohibited transfers except by order form. But he testified that because of constitutional doubts:

'(a)t this point, this bill, like the National Firearms Act, departs from the plan of the Harrison Narcotic Act which limits the right to purchase narcotic drugs to those persons who are permitted to register under that act. * * *

'(I)n order to obviate the possibility of (an) attack upon the constitutionality of this bill, it, like the National Firearms Act, permits the transfer of marihuana to nonregistered persons upon the payment of a heavy transfer tax. The bill would permit the transfer of marihuana to anyone, but would impose a $100 per ounce tax upon a transfer to a person who might use it for purposes which are dangerous and harmful to the public * * *.'27

Mr. Hesterw as also the first witness before a subcommittee of the Senate Finance Committee. There he testified in less detail, stating at different points that the purpose of the transfer provisions was 'to discourage the widespread use of the drug by smokers and drug addicts,'28 'to render extremely difficult the acquisition of marihuana by persons who desire it for illicit uses,'29 'to prevent transfers to persons who would use marihuana for undersirable purposes,'30 and 'through the $100 transfer tax to prevent the drug from coming into the hands of those who will put it to illicit uses.'31

The House and Senate reports describe the purposes of the transfer provisions largely in the language of Mr. Hester's testimony. The House report declares that the purpose was 'to discourage the widespread use of the drug by smokers and drug addicts,'32 to 'render extremely difficult the acquisition of marihuana by persons who desire it for illicit uses,'33 and 'through the $100 transfer tax to prevent the drug from coming into the hands of those who will put it to illicit uses.'34 In discussing the issue of constitutionality, the report recites that '(t)he law is * * * settled that Congress has the power to enact a tax which is so heavy as to discourage the transactions or activities taxed'35 and states that '(t)hese cases sustain the $100 tax imposed * * * upon transfers * * * to unregistered persons.'36 The Senate report, without discussing constitutionality, otherwise states the purpose of the transfer provisions in the very same words as the House report.37 Thus, the committee reports confirm Mr. Hester's account of the bill's purposes. In short, the legislative history fully accords with the statutory language.

Upon this evidence, we have no hesitation in concluding that the interpretation which the Government would give to the transfer provisions is, contrary to the manifest congressional intent that transfers to nonregistrants be taxed, not forbidden. Insofar as the regulations which require comparison of signatures necessarily compel the result urged by the Government, they must be regarded as contrary to the statute and hence beyond the scope of the regulation-making authority which was delegated by Congress.38 It is true that these regulations were promulgated in 1937, and that Congress re-enacted the entire Act in 1954, while they were in effect. However, the scanty legislative history accompanying that re-enactment gives no hint that Congress knew of these particular regulations, much less of the indirect impact which the Government now ascribes to them.39 As we recently noted in Massachusetts Trustees of Eastern Gas and Fuel Associates v. United States, 377 U.S. 235, 241, 242, 84 S.Ct. 1236, 1241—1242, 12 L.Ed.2d 268 (1964), congressional re-enactment of a statute, even without any apparent knowledge of a particular regulation, can 'strengthen to some extent' the regulation's claim to validity, but re-enactment cannot save a regulation which 'contradict(s) the requirements' of the statute itself. When a regulation conflicts with the statute, the fact of subsequent re-enactment 'is immaterial, for Congress could not add to or expand (the) statute by impliedly approving the regulation.' Commissioner of Internal Revenue v. Acker, 361 U.S. 87, 93, 80 S.Ct. 144, 148, 4 L.Ed.2d 127 (1959).40

Nor are we persuaded by the Government's argument that its construction has been followed by the Internal Revenue Service and the Bureau of Narcotics ever since the passage of the Act, and that this 'long-standing' interpretation by the agencies charged with administering the Act should be controlling. We have often recognized that, as a general matter, a long-standing, contemporaneous construction of a statute by the administering agencies is 'entitled to great weight,' FTC v. Mandel Bros., 359 U.S. 385, 391, 79 S.Ct. 818, 823, 3 L.Ed.2d 893 (1959), and will be 'show(n) great deference,' Udall v. Tallman, 380 U.S. 1, 16, 85 S.Ct. 792, 801, 13 L.Ed.2d 616 (1965).41 However, in this instance the Government admits that until our decisions last term in Marchetti, Grosso, and Haynes, the alleged interpretation had been made known only through the regulations themselves, since there apparently had never been an application by a nonregistrant to prepay the transfer tax. Moreover, in its brief in this Court in United States v. Sanchez, 340 U.S. 42, 71 S.Ct. 108, 95 L.Ed. 47 (1950), the United States plainly took the position that the Act imposed only a tax and not a prohibition on transfers to nonregistrants,42 implying that at that time the alleged administrative construction was unknown even to those charged with representing the United States in this Court. In these circumstances, the alleged administrative construction can furnish no additional support for the Government's argument.

The foregoing shows that at the time petitioner acquired marihuana he was confronted with a statute which on its face permitted him to acquire the drug legally, provided he paid the $100 per ounce transfer tax and gave incriminating information, and simultaneously with a system of regulations which, according to the Government, prohibited him from acquiring marihuana under any conditions. We have found those regulations so out of keeping with the statute as to be ultra vires. Faced with these conflicting commands, we think petitioner would have been justified in giving precedence to the higher authority: the statute.43 "(L)iteral and full compliance' with all the statutory requirements'44 would have entailed a very substantial risk of self-incrimination. See supra, at 16—18.

The United States has not urged us, as it did in Marchetti, Grosso, and Haynes, to avoid this constitutional difficulty by placing restrictions upon the use of information gained under the transfer provisions. We declined to impose use restrictions in those cases because we found that the furnishing of information to interested prosecutors was a 'significant element of Congress' purposes in adopting' the statute there involved. Marchetti v. United States, supra, 390 U.S., at 59, 88 S.Ct. at 708 (1968).45 The text and legislative history of the Marihuana Tax Act plainly disclose a similar congressional purpose. As has been noted, 26 U.S.C. § 4773 requires that copies of order forms be kept available for inspection by state and local officials, and that copies be furnished to such officials on request. The House and Senate reports both state that one objective of the Act was 'the development of an adequate means of publicizing dealings in marihuana in order to tax and control the traffic effectively.'46 In short, we think the conclusion inescapable that the statute was aimed at bringing to light transgressions of the marihuana laws. Hence, as in last Term's cases, we decline to impose use restrictions and are obliged to conclude that a timely and proper assertion of the privilege should have provided a complete defense to prosecution under § 4744(a)(2).

There remain the further questions whether this petitioner's claim of the privilege was timely and whether it was waived. As for timeliness, petitioner did not assert the privilege as a defense to the § 4744(a) count until his motion for a new trial. The Court of Appeals evidently regarded the claim as timely, for it rejected it on the merits both in its original opinion and in its denial of rehearing. See 383 F.2d, at 870; 392 F.2d, at 221 222. The Government does not contend that the claim of the privilege was untimely. Petitioner's trial occurred before our decisions in Marchetti, Grosso, and Haynes, and the Court of Appeals for the Fifth Circuit had recently rejected an identical self-incrimination claim. See Haynes v. United States, 339 F.2d 30 (1964). Although it would have been preferable for petitioner to have asserted the privilege at trial, we hold that in the circumstances of this case his failure to raise the issue at that time did not amount to a waiver of the privilege. See Grosso v. United States, 390 U.S. 62, 70—71, 88 S.Ct. 709, 714—715, 19 L.Ed.2d 906 (1968).

In denying Leary's petition for rehearing, the Court of Appeals, in addition to holding the privilege generally inapplicable to prosecutions under § 4744(a), found that petitioner's claim of the privilege was improper because he 'took the stand and affirmatively waived the privilege * * * by testifying fully to the details of his acquisition and transportation of marihuana without having paid the tax * * *.' 392 F.2d, at 222. In relying for that proposition on the statement in Marchetti that our decision in that case would not provide a shield for any taxpayer who was 'outside the privilege's protection,' 390 U.S., at 61, 88 S.Ct., at 709, we think the Court of Appeals misconceived the thrust of that dictum. The aspect of the self-incrimination privilege which was involved in Marchetti, and which petitioner asserts here, is not the undoubted right of an accused to remain silent at trial. It is instead the right not to be criminally liable for one's previous failure to obey a statute which required an incriminatory act. Thus, petitioner is not asserting that he had a right to stand mute at his trial but that he cannot be convicted for having failed to comply with the transfer provisions of the Act t the time he acquired marihuana in 1965. His admission at trial that he had indeed failed to comply with the statute was perfectly consistent with the claim that that omission was excused by the privilege. Hence, it could not amount to a waiver of that claim.

The Government suggests that petitioner waived his right to plead self-incrimination in yet another way, by testifying at trial that he had violated the statute for reasons entirely unrelated to fear of self-incrimination. It is true that some portions of petitioner's testimony indicate that his noncompliance was motivated, at least in part, by his conviction that the Act imposed an illegal tax upon religion or upon the cpursuit of knowledge'47 and by his belief that, in consequence of the system of regulations and administrative practice described above, he would not be permitted to pay the tax.48 However, other parts of petitioner's testimony clearly indicate that he also was influenced by an apprehension that by trying to pay the tax he might incriminate himself.49 We cannot say that petitioner's testimony, taken as a whole, amounted to a waiver of the privilege. We conclude that petitioner's invocation of the privilege was proper and that it should have provided a full defense to the third count of the indictment. Accordingly, we reverse petitioner's conviction under 26 U.S.C. § 4744(a)(2).

Next, we consider whether, in the circumstances of this case, the application of the presumption contained in 21 U.S.C. § 176a denied petitioner due process of law.

Insofar as here relevant, § 176a imposes criminal punishment upon every person who:

'Knowingly, with intent to defraud the United States, imports or brings into the United States marihuana contrary to law * * *, or receives, conceals, buys, sells, or in any manner facilitates the transportation, concealment, or sale of such marihuana after being imported or brought in, knowing the same to have been imported or brought into the United States contrary to law * * *.'

A subsequent paragraph establishes the presumption now under scrutiny:

'Whenever on trial for a violation of this subsection, the defendant is shown to have or to have had the marihuana in his possession, such possession shall be deemed sufficient evidence to authorize conviction unless the defendant explains his possession to the satisfaction of the jury.'

The second count of the indictment charged petitioner with having violated the 'transportation' and 'concealment' provisions of § 176a.50 Petitioner admitted at trial that he had acquired marihuana in New York; had driven with it to Laredo, Texas; had continued across the bridge to the Mexican customs station; and then had returned to the United States. He further testified that he did not know where the marihuana he acquired had been grown.51

In view of this testimony, the trial court instructed the jury that it might find petitioner guilty of violating s 176a on either of two alternative theories. Under the first or 'South-North' theory, a conviction could have been based solely upon petitioner's own testimony that the marihuana had been brought back from Mexico into the United States and that with knowledge of that fact petitioner had continued to transport it. Under the second or 'North-South' theory, the conviction would have depended partly upon petitioner's testimony that he had transported the marihuana from New York to Texas and partly upon the challenged presumption.52

The Government contends that by giving testimony at trial which established all elements of the offense under the 'South-North' theory, and by failing to object to the jury instructions on the ground now advanced, petitioner foreclosed himself from raising the point thereafter. We cannot agree. Even assuming that petitioner's testimony did supply all the evidence required for a valid conviction under the 'South-North' theory, the jury nevertheless was told that it could alternatively convict with the aid of the presumption under the 'North-South' theory. For all we know, the conviction did rest on that ground. It was long been settled that when a case is submitted to the jury on alternative theories the unconstitutionality of any of the theories requires that the conviction be set aside. See, e.g., Stromberg v. California, 283 U.S. 359, 51 S.Ct. 532, 75 L.Ed. 1117 (1931).

It is true that petitioner did not object to the jury instructions on the basis of the presumption's alleged unconstitutionality.53 However, he did rely upon that ground in his previous motion for a directed verdict at the close of the prosecution's case and urged it again in his subsequent motion for a new trial.54 Both motions were denied. The Court of Appeals considered petitioner's constitutional argument on the merits, and rejected it. See 383 F.2d, at 868—870. In these circumstances, we conclude that the question is properly before us.55

By what criteria is the constitutionality of the § 176a presumption to be judged?

Early decisions of this Court set forth a number of different standards by which to mes ure the validity of statutory presumptions.56 However, in Tot v. United States, 319 U.S. 463, 63 S.Ct. 1241, 87 L.Ed. 1519 (1943), the Court singled out one of these tests as controlling, and the Tot rule has been adhered to in the two subsequent cases in which the issue has been presented. The Tot Court had before it a federal statute57 which, as construed, made it a crime for one previously convicted of a crime of violence to receive any firearm or ammunition in an interstate transaction. The statute further provided that 'the possession of a firearm or ammunition by any such person shall be presumptive evidence that such firearm or ammunition was shipped or transported or received, as the case may be, by such person in violation of this Act.'

The Court, relying upon a prior decision in a civil case,58 held that the 'controlling' test for determining the validity of a statutory presumption was 'that there be a rational connection between the fact proved and the fact presumed.' 319 U.S., at 467, 63 S.Ct. at 1245. The Court stated:

'Under our decisions a statutory presumption cannot be sustained if there be no rational connection between the fact proved and the ultimate fact presumed, if the inference of the one from proof of the other is arbitrary because of lack of connection between the two in common experience. This is not to say that a valid presumption may not be created upon a view of relation broader than that a jury might take in a specific case. But where the inference is so strained as not to have a reasonable relation to the circumstance of life as we know them it is not competent for the legislature to create it as a rule governing the procedure of courts.' 319 U.S., at 467—468, 63 S.Ct., at 1245. (footnotes omitted).

The Tot Court reduced to the status of a 'corollary' another test which had some support in prior decisions:59 whether it was more convenient for the defendant or for the Government to supply proof of the ultimate fact which the presumption permitted to be inferred. The Court stated that '(t)he argument from convenience is admissible only where the inference is a permissible one * * *.' 319 U.S., at 469, 63 S.Ct., at 1246. The Court rejected entirely another suggested test with some backing in the case law,60 according to which the presumption should be sustained if Congress might legitimately have made it a crime to commit the basic act from which the presumption allowed an inference to be drawn.61 The Tot Court stated simply that 'for whatever reason' Congress had not chosen to make the basic act a crime. Id., at 472, 63 S.Ct., at 1247.

Applying h e 'rational connection' test, the Court held the Tot presumption unconstitutional. The Court rejected the contention that because most States forbade intrastate acquisition of firearms without a record of the transaction or registration of ownership it could be inferred merely from possession that an acquisition which did not meet these requirements must have been interstate, noting the alternative possibilities of unlawful intrastate acquisition and interstate shipment prior to the beginning of state regulation. See id., at 468, 63 S.Ct., at 1245.62

The two subsequent cases in which this Court ruled upon the constitutionality of criminal statutory presumptions, United States v. Gainey, 380 U.S. 63, 85 S.Ct. 754, 13 L.Ed.2d 658 (1965), and United States v. Romano, 382 U.S. 136, 86 S.Ct. 279, 15 L.Ed.2d 210 (1965), involved companion sections of the Internal Revenue Code dealing with illegal stills. The presumption in Gainey was worded similarly to the one at issue here; it permitted a jury to infer from a defendant's presence at an illegal still that he was 'carrying on' the business of a distiller 'unless the defendant explains such presence to the satisfaction of the jury * * *.' See 26 U.S.C. §§ 5601(a)(4), 5601(b)(2).

We held that the Gainey presumption should be tested by the 'rational connection' standard announced in Tot. We added:

'The process of making the determination of rationality is, by its nature, highly empirical, and in matters not within specialized judicial competence or completely commonplace, significant weight should be accorded the capacity of Congress to amass the stuff of actual experience and cull conclusions from it.' 380 U.S., at 67, 85 S.Ct., at 757.

Applying these principles, we sustained the Gainey presumption, finding that it 'did no more than 'accord to the evidence, if unexplained, its natural probative force." 380 U.S., at 71, 85 S.Ct., at 759.

The presumption under attack in United States v. Romano, supra, was identical to that in Gainey except that it authorized the jury to infer from the defendant's presence at an illegal still that he had possession, custody, or controll of the still. See 26 U.S.C. §§ 5601(a)(1), 5601(b)(1). We held this presumption invalid. While stating that the result in Gainey was entirely justified because '(p)resence at an operating still is sufficient evidence to prove the charge of 'carrying on' because anyone present at the site is very probably connected with the illegal enterprise,' 382 U.S., at 141, 86 S.Ct., at 282, we concluded:

'Presence is relevant and admissible evidence in a trial on a possession charge; but absent some showing of the defendant's function at the still, its connection with possession is too tenuous to permit a reasonable inference of guilt—'the inference of the one from proof of the other is arbitrary * * *.' Tot v. United States, 319 U.S. 463, 467, 63 S.Ct. 1241, 1245, 87 L.Ed. 1519.' Ibid.63

The upshot of Tot, Gainey, and Romano is, we think, that a criminal statutory presumption must be regarded as 'irrational' or 'arbitrary,' and hence unconstitutional, unless it can at least be said with substantial assurance that the presumed fact is more likely than not to flow from the proved fact on which it is made to depend.64 And in the judicial assessment the congressional determination favoring the particular r esumption must, of course, weigh heavily.

How does the § 176a presumption fare under these standards?

So far as here relevant, the presumption, quoted supra, at 30, authorizes the jury to infer from a defendant's possession of marihuana two necessary elements of the crime: (1) that the marihuana was imported or brought into the United States illegally; and (2) that the defendant knew of the unlawful importation or bringing in.65 Petitioner argues that neither inference is valid, citing undisputed testimony at his trial to the effect that marihuana will grow anywhere in the United States, and that some actually is grown here.66 The Government contends, on the other hand, that both inferences are permissible. For reasons that follow, we hold unconstitutional that part of the presumption which relates to a defendant's knowledge of illegal importation. Consequently, we do not reach the question of the validity of the 'illegal importation' inference.

With regard to the 'knowledge' presumption, we believe that Tot and Romano require that we take the statute at face value and ask whether it permits conviction upon insufficient proof of 'knowledge,' rather than inquire whether Congress might have made possession itself a crime.67 In order thus to determine the constitutionality of the 'knowledge' inference, one must have direct or circumstantial data regarding the beliefs of marihuana users generally about the source of the drug they consume. Such information plainly is 'not within specialized judicial competence or completely commonplace,' United States v. Gainey, supra, 380 U.S. at 67, 85 S.Ct., at 757. Indeed, the presumption apparently was enacted to relieve the Government of the burden of having to adduce such evidence at every trial, and none was introduced by the prosecution at petitioner's trial. Since the determination of the presumption's constitutionality is 'highly empirical,' ibid., it follows that we must canvass the available, pertinent data.

Of course, it must be kept in mind that 'significant weight should be accorded the capacity of Congress to amass the stuff of actual experience and cull conclusions from it.' Ibid. However, it quickly becomes apparent that the legislative record does not supply an adequate basis upon which to judge the soundness of the 'knowledge' part of the presumption. We have therefore taken other materials into account as well, in an effort to sustain the presumption. In so doing, we have not confined ourselves to data available at the time the presumption was enacted in 1956, but have also considered more recent information, in order both to obtain a broader general background and to ascertain whether the intervening years have witnessed significant changes which mih t bear upon the presumption's validity.68

As has been noted, we do not decide whether the presumption of illegal importation is itself constitutional. However, in view of the paucity of direct evidence as to the beliefs of marihuana smokers generally about the source of their marihuana, we have found it desirable to survey data concerning the proportion of domestically consumed marihuana which is of foreign origin, since in the absence of better information the proportion of marihuana actually imported surely is relevant in deciding whether marihuana possessors 'know' that their marihuana is imported.

Since the importation question is a subsidiary one, we take it up first, beginning, of course, with the legislative history of § 176a. The House and Senate committee reports and the floor debates are relatively unhelpful.69 More informative are the records of extensive hearings before House and Senate committees.70 Near the outset of the Senate committee hearings, the then Commissioner of Narcotics, Harry J. Anslinger, estimated that 90% of all marihuana seized by federal authorities had been smuggled from Mexico, and that although 'there is considerable volunteer growth from old plantings in the Middle West * * *, (t)here is very little of the local land used because it just does not have the advantage of the long summer growing, and (domestic marihuana) is not as potent as the Mexican drug.'71 A number of officials responsible for enforcing the narcotics laws in various localities estimated that a similar proportion of the marihuana consumed in their areas was of Mexican origin.72

On the other hand, written material inserted in the record of the Senate hearings included former testimony of an experienced federal customs agent before another Senate committee, to the effect that high-quality marihuana was being grown near the Texas cities of Laredo and Brownsville.73 A written report of the Ohio Attorney General recited that marihuana 'may grow unnoticed along roadsides and vacant lots in many parts of the country,'74 and a Philadelphia Police Academy bulletin stated that: 'Plenty of (marihuana) is found growing in this city.'75

Examination of periodicals and books published since the enactment of the presumption leaves no doubt that in more than a dozen intervening years there have been great changes in the extent and nature of marihuana used in this country. With respect to quantity, one readily available statistic is indicative: the amount of marihuana seized in this country by federal authorities has jumped from about 3,400 pounds in 1956 to b out 61,400 pounds in 1967.76 With regard to nature of use, the 1955 hearing records and other reports portray marihuana smoking as at that time an activity almost exclusively of unemployed or menially employed members of racial minorities.77 Current periodicals and books, on the other hand, indicate that marihuana smoking has become common on many college campuses and among persons who have voluntarily 'dropped out' of American society in protest against its values, and that marihuana smokers include a sizeable number of young professional persons.78

Despite these undoubted changes, the materials which we have examined point quite strongly to the conclusion that most domestically consumed marihuana is still of foreign origin. During the six years 1962—1967, some 79% of all marihuana seized by federal authorities was seized in attempted smuggling at ports and borders.79 The Government informs us that a considerable part of the internally seized marihuana bore indications of foreign origin.80 While it is possible that these facts reflect only the deployment of federal narcotics forces, rather than the actual proportion of imported to domestic marihuana, almost all of the authorities which we have consulted confirm that the preponderance of domestically consumed marihuana is grown in Mexico.81

Petitioner makes much of statistics showing the number of acres of domestic marihuana destroyed annually by state and federal authorities, pointing out that if harvested the destroyed acreage could in each year have accounted for all marihuana estimated to have been consumed in the United States,82 and that no one knows how many acres escape destruction. However, several factors weaken this argument from domestic growth. First, the number of acres annually destroyed declined by a factor of three between 1959 and 1967,83 while during the same period the consumption of marihuana, as measured b federal seizures, rose twenty-fold.84 Assuming constant diligence on the part of those charged with destruction, this would indicate that in 1967 a much smaller share of the market was domestically supplied than in 1959. Second, while the total number of acres annually destroyed has indeed been large enough to furnish all domestically consumed marihuana,85 the state-by-state breakdowns which are available for the years 1964 1967 reveal that in each of those years more than 95% of the destroyed acreage was in two midwestern states, Illinois and Minnesota.86 The large, recurrent marihuana acreages discovered in those States can plausibly be ascribed to the 'volunteer growth from old plantings in the Middle West' about which Commissioner Anslinger testified,87 while illicit cultivators of marihuana would be likely to choose States with sparser populations and more favorable climates.88 Third and last, reports of the Bureau of Narcotics and testimony of its agents indicate that in its far-reaching investigations the Bureau has never encountered a system for distributing sizeable quentities of domestically grown marihuana.89 In contrast, the Bureau has found evidence of many large-scale distribution systems with sources in Mexico.90

The Government urges that once it is concluded that most domestically consumed marihuana comes from abroad—a conclusion which we think is warranted by the data just examined—we must uphold the 'knowledge' part of the presumption in light of this Court's decision in Yee Hem v. United States, 268 U.S. 178, 45 S.Ct. 470, 69 L.Ed. 904 (1925). In that case, the Court sustained a presumption which was virtually identical to the one at issue here except that the forbidden substance was smoking opium rather than marihuana. With respect to the inference of knowledge from possession which was authorized by that presumption, the Court said:

'Legii mate possession (of opium), unless for medicinal use, is so highly improbable that to say to any person who obtains the outlawed commodity, 'since you are bound to know that it cannot be brought into this country at all, except under regulation for medicinal use, you must at your peril ascertain and be prepared to show the facts and circumstances which rebut, or tend to rebut, the natural inference of unlawful importation, or your knowledge of it,' is not such an unreasonable requirement as to cause it to fall outside the constitutional power of Congress.' 268 U.S., at 184, 45 S.Ct., at 471.

The Government contends that Yee Hem requires us to read the § 176a presumption as intended to put every marihuana smoker on notice that he must be prepared to show that any marihuana in his possession was not illegally imported, and that since the possessor is the person most likely to know the marihuana's origin it is not unfair to require him to adduce evidence on that point. However, we consider that this approach, which closely resembles the test of comparative convenience in the production of evidence,91 was implicitly abandoned in Tot v. United States, 319 U.S. 463, 63 S.Ct. 1241, 87 L.Ed. 1519 (1943). As was noted previously, the Tot Court confronted a presumption which allowed a jury to infer from possession of a firearm that it was received in interstate commerce. Despite evidence that most States prohibited unregistered and unrecorded acquisition of firearms, the Court did not read the statute as notifying possessors that they must be prepared to show that they received their weapons in intrastate transactions, as Yee Hem would seem to dictate. Instead, while recognizing that 'the defendants * * * knew better than anyone else whether they acquired the firearms or ammunition in interstate commerce,' 319 U.S., at 469, 63 S.Ct., at 1246, the Court held that because of the danger of overreaching it was incumbent upon the prosecution to demonstrate that the inference was permissible before the burden of coming forward could be placed upon the defendant. This was a matter which the Yee Hem Court either thought it unnecessary to consider or assumed when it described the inference as 'natural.'92

We therefore must consider in detail whether the available evidence supports the conclusion that the 'knowledge' part of the § 176a presumption is constitutional under the standard established in Tot and adhered to in Gainey and Romano that is, whether it can be said with substantial assurance that one in possession of marihuana is more likely than not to know that his marihuana was illegally imported.

Even if we assume that the previously assembled data are sufficient to justify the inference of illegal importation, see supra, at 44, it by no means follows that a majority of marihuana possessors 'know'93 that their marihuana was illegally imported. And such proposition would depend upon an intermediate premise: that most marihuana possessors are aware of the level of importation and have deduced that their own marihuana was grown abroad. This intermediate step might be thought justified by common sense if it were proved that little or no marihuana is grown in this country. Short of such a showing, not here present, we do not believe that the inference of knowledge can be sustained solely because of the assumed validity of the 'importation' presumption.

Once it is established that a significant percentage of domestically consumed marihuana may not have been imported at all, then it can no longer be postulated, without proof, that possessors will be even roughly aware of the proportion actually imported. We conclude that in order to sustain the inference of knowledge we must find on the basis of the available materials that a majority of marihuana possessors either are cognizant of the apparently high rate of importation or otherwise have become aware that their marihuana was grown abroad.

We can imagine five ways in which a possessor might acquire such knowledge: (1) he might be aware of the proportion of domestically consumed marihuana which is smuggled from abroad and deduce that his was illegally imported; (2) he might have smuggled the marihuana himself; (3) he might have learned by indirect means that the marihuana consumed in his locality or furnished by his supplier was smuggled from abroad; (4) he might have specified foreign marihuana when making his 'buy', or might have been told the source of the marihuana by his supplier; (5) he might be able to tell the source from the appearance, packaging, or taste of the marihuana itself.

We treat these five possibilities seriatim, in light of the available materials, beginning in each instance with the legislative record. We note at the outset that although we have been able to discover a good deal of relevant secondary evidence, we have found none of the best kind possible—testimony of marihuana users about their own beliefs as to origin, or studies based upon interviews in which users were asked about this matter. The committee hearings which preceded passage of § 176a included testimony by many marihuana smokers, but none was ever asked whether he knew the origin of the marihuana he smoked. It should also be kept in mind that the great preponderance of marihuana smokers are 'occasional' rather than 'regular' users of the drug,94 and that 'occasional' smokers appear to be arrested disproportionately often, due to their inexpertness in taking precautions.95 'Occasional' users are likely to be less informed and less particular about the drug they smoke;96 hence, it is less probable that they will have learned its source in any of the above ways.

The first possibility is that a possessor may have known the proportion of imported to domestic marihuana and have deduced that his own marihuana was grown abroad. The legislative record is of no assistance in evaluating this possibility. Such indirect evidence as we have found points to the conclusion that while most marihuana users probably know that some marihuana comes from Mexico, it is also likely that the great majority either have no knowledge about the proportion which is imported or believe that the proportion is considerably lower than may actually be the case.97

The second possibility is that a possessor may know the origin of his marihuana because he smuggled it into the United States himself. The legislative record is unhelpful in estimating the proportion of possessors whof all into this class. Other sources indicate that there are a considerable number of smokers who 'smuggle their own,' but that the great majority of possessors have obtained their marihuana from suppliers in this country.98

The legislative record is also uninformative about the possibility that a possessor may have learned the source of his marihuana by indirect means. Other sources reveal that imported marihuana usually passes through a number of hands before reaching the consumer, and that the distribution system is kept secret.99 It would appear that relatively few consumers know the origin of their marihuana by indirect means.

The fourth possibility is that the possessor may have specified foreign marihuana when making his purchase or may have been told by his supplier that the marihuana was grown abroad. The legislative record is somewhat more helpful with respect to this possibility, for it does contain statements to the effect that Maxican marihuana is more potent than domestic and is consequently preferred by smokers.100 However, the legislative record also contains testimony by a customs agent that Texas marihuana is as 'good' as that from Mexico.101 Most authorities state that Mexican marihuana generally does have greater intoxicating power than domestic marihuana, due to the higher temperatures and lower humidity usually encountered in Mexico.102 There are some indications that smokers are likely to prefer Mexican marihuana,103 but there is nothing to show that purchasers commonly specify Mexican marihuana when making a 'buy.' It appears that suppliers of marihuana occasionally volunteer the place of origin,104 but we have found no hint that this is usually done, and there are indications that if the information is not volunteered the buyer may be reluctant to ask, for fear of being thought an informer.105 We simply are unable to estimate with any accuracy, on the basis of these data, what proportion of marihuana possessors have learned the origin of their marihuana in this way. It is certainly not a majority; but whether it is a small minority or a large one we are unable to tell.

The fifth possibility is that a smoker may be able to tell the source of his marihuana from its appearance, packaging, or taste. As for appearance, it seems that there is only one species of marihuana, and that even experts are unable to tell by eye where a particular sample was grown.106 The Court of Appeals for the Ninth Circuit did find in Caudillo v. United States, 253 F.2d 513 (1958), on the basis of trial testimony, that 'unmanicured' or 'rough' marihuana—that is, marihuana containing some seeds and stems, as well § leaves—was much more likely to come from Mexico than from California; this was because the presence of seeds implied that the plant had been allowed to mature and evidence showed that California growers almost always harvested the plant before that stage. However, we have found nothing to indicate that this distinction holds good in other areas of the country, or that marihuana possessors are likely to realize its significance.

With respect to packaging, there is evidence that Mexican marihuana is commonly compressed into distinctive 'bricks' and then wrapped in characteristically Mexican paper.107 Yet even if it is assumed that most Mexican marihuana bears such sistinguishing marks when first brought into this country, there is no indication that they normally are still present when it reaches the consumer. The packaging method just mentioned apparently is intended to facilitate transportation of relatively large quantities of mrihuana. A 'brick' appears usually to contain about one kilogram of marihuana,108 and relatively few consumers sales will involve such a large amount, since a kilogram of marihuana will furnish some 3,300 marihuana cigarettes.109 Smokers appear usually to purchase marihuana by the 'bag'—about one-fifth ounce; by the 'can'—about one ounce; or by the pound.110 Hence, after importation '(t)he wholesalers will repackage the marihuana into smaller packages, * * * and they will do it in various ways.'111 We infer that only a small percentage of smokers are likely to learn of the drug's origin from its packaging.

With respect to taste, the Senate hearing record contains the statement of a federal customs agent that: 'A good marihuana smoker can probably tell good marihuana from bad.'112 As has been seen, there is a preponderance of opinion to the effect that Maxican marihuana is more potent than domestic.113 One authority states that purchasers of marihuana commonly sample the product before making a 'buy.'114 However, the agent quoted above also asserted that some 'good' marihuana was grown in Texas. And the account of the sampling custom further states that tasting is merely a ritual since '(u)sually the intoxication will not differ much from one cigarette to another * * *.'115 Once again, we simply are unable to estimate what proportion of mrihuana possessors are capable of 'placing' the marihuana in their possession by its taste, much less what proportion actually have done so by the time they are arrested.

We conclude that the 'knowledge' aspect of the § 176a presumption cannot be upheld without making serious incursions into the teachings of Tot, Gainey, and Romano. In the context of this part of the statute, those teachings require that it be determined with substantial assurance that at least a majority of marihuana possessors have learned of the foreign origin of their marihuana through one or more of the ways discussed above.

We find it impossible to make such a determination. As we have seen, the materials at our disposal leave us at large t estimate even roughly the proportion of marihuana possessors who have learned in one way or another the origin of their marihuana. It must also be recognized that a not inconsiderable proportion of domestically consumed marihuana appears to have been grown in this country, and that its possessors must be taken to have 'known,' if anything, that their marihuana was not illegally imported. In short, it would be no more than speculation were we to say that even as much as a majority of possessors 'knew' the source of their marihuana.116

Nor are these deficiencies in the foundation for the 'knowledge' presumption overcome by paying, as we do, the utmost deference to the congressional determination that this presumption was warranted. For Congress, no less than we, is subject to constitutional requirements, and in this instance the legislative record falls even shorter of furnishing an adequate foundation for the 'knowledge' presumption than do the more extensive materials we have examined.

We thus cannot escape the duty of setting aside petitioner's conviction under Court 2 of this indictment.

For the reasons stated in Part I of this opinion we reverse outright the judgment of conviction on Count 3 of the indictment. For the reasons stated in Part II, we reverse the judgment of conviction on Count 2 and remand the case to the Court of Appeals for further proceedings consistent with this opinion. We are constrained to add that nothing in what we hold today implies any constitutional disability in Congress to deal with the marihuana traffic by other means.

Reversed and remanded.

Mr. Chief Justice WARREN joins Part II of the opinion of the Court and, considering himself bound by the decisions in Marchetti v. United States, 390 U.S. 39, 88 S.Ct. 697, 19 L.Ed.2d 889 (1968); Grosso v. United States, 390 U.S. 62, 88 S.Ct. 709, 19 L.Ed.2d 906 (1968), and Haynes v. United States, 390 U.S. 85, 88 S.Ct. 722, 19 L.Ed.2d 923 (1968), concurs in the result as to Part I.

Mr. Justice STEWART, concurring.

I join Part II of the Court's opinion. As to Part I, I have before now expressed my conviction that the Fifth Amendment guarantee against compulsory self-incrimination was originally intended to do no more than confer a testimonial privilege in a judicial proceeding.1 But the Court through the years has drifted far from that mooring; the Marchetti and Grosso cases2 are simply the most recent in a long line of decisions marking the extent of the drift. Perhaps some day the Court will consider a fundamental re-examination of its decisions in this area, in the light of the original constitutional meaning. Until that day comes, it seems to me that the authoritative weight of precedent permits no escape from the conclusion reached by the Court in this case. I therefore join its opinion and judgment.

Mr. Justice BLACK, concurring in the result.

I concur in the Court's outright reversal of the petitioner's conviction on Count 3 of the indictment for the reasons set out in Part I of the Court's opinion.

I also concur in reversal of the petitioner's conviction on Count 2 of the indictment, based on 21 U.S.C. § 176a. That section makes it a crime to import marihuana into the United States or to receive, conceal, or transport it, knowing it to have been imported contrary to law, and then goes on to provide that the mere possession of marihuana shall be 'deemed sufficient evidence to authorize conviction unless the defendant explains his possession to the satisfaction of the jury.' The trial court in this case charged the jury that proof that petitioner merely had possession of marihuana was sufficient to authorize a finding that he knew it had been imported or brought into the United States contrary to law. It is clear beyond doubt that the fact of possession alone is not enough to support an inference that the possessor knew it had been imported. Congress has no more constitutional power to tell a jury it can convict upon any such forced and baseless inference than it has power to tell juries they can convict a defendant of a crime without any evidence at all from which an inference of guilt could be drawn. See Thompson v. Louisville, 362 U.S. 199, 80 S.Ct. 624, 4 L.Ed.2d 654 (1960). Under our system of separation of powers, Congress is just as incompetent to instruct the judge and jury in an American court what evidence is enough for conviction as the courts are to tell the Congress what policies it must adopt in writing criminal laws. The congressional presumption, therefore, violates the constitutional right of a defendant to be tried by jury in a court set up in accordance with the commands of the Constitution. It clearly deprives a defendant of his right not to be convicted and punished for a crime without due process of law, that is, in a federal case, a trial before an independent judge, after an indictment by grand jury, with representation by counsel, an opportunity to summon witnesses in his behalf, and an opportunity to confront the witnesses against him. This right to a full-fledged trial in a court of law is guaranteed to every defendant by Article III of the Constitution, in the Sixth Amendment, and by the Fifth and Fourteenth Amendments' promises that no person shall be deprived of his life, liberty, or property without due process of law—that is A trial according to the law of the land, both constitutional and statutory.

It is for these reasons, and not because I think the law is "irrational' or 'arbitrary,' and hence unconstitutional,' ante, at 30, that I would invalidate this presumption. I am firmly and profoundly opposed to construing 'due process' as authorizing this Court to invalidate statutes on any such nebulous grounds. My quite different reasons for holding that the presumption does deny due process of law, that is the benefit of the 'law of the land,' have been fully set out in many opinions, including, for illustration, my concurring opinion in Tot v. United States, 319 U.S. 463, 473, 63 S.Ct. 1241, 87 L.Ed. 1519 (1943), and my dissenting opinion in United States v. Gainey, 380 U.S. 63, 74, 85 S.Ct. 754, 761, 13 L.Ed.2d 658 (1965).