                    FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA,                      No. 05-50112
                Plaintiff-Appellee,
               v.                                D.C. No.
                                               CR-01-00024-RT
JAE GAB KIM,
                                                  OPINION
             Defendant-Appellant.
                                         
        Appeal from the United States District Court
           for the Central District of California
         Robert J. Timlin, Senior Judge, Presiding

                   Argued and Submitted
             March 6, 2006—Pasadena, California

                      Filed April 10, 2006

   Before: M. Margaret McKeown and Marsha S. Berzon,
    Circuit Judges, and Samuel P. King,* Senior Judge.

                   Opinion by Judge Berzon




   *The Honorable Samuel P. King, Senior United States District Judge
for the District of Hawaii, sitting by designation.

                               3921
3924               UNITED STATES v. KIM


                       COUNSEL

William J. Genego, Esq., Santa Monica, California, argued
the case and was on the briefs for the defendant-appellant.

Gregory A. Lesser, Assistant U.S. Attorney, Los Angeles,
California, argued the case and was on the briefs for the
plaintiff-appellee; Debra Wong Yang, U.S. Attorney and
Thomas P. O’Brien, Assistant U.S. Attorney, Los Angeles,
California, were on the briefs for the plaintiff-appellee.
                     UNITED STATES v. KIM                 3925
                         OPINION

BERZON, Circuit Judge:

   Pseudoephedrine, a “listed chemical” under a federal drug
statute, 21 U.S.C. § 802(33) & (34)(K), is an ingredient in
many over-the-counter cold medications. It can also be used
to manufacture methamphetamine, a controlled substance
under 21 U.S.C. § 812. Both the United States and California
have statutes prohibiting over-the-counter sales of drugs con-
taining pseudoephedrine in certain instances. See 21 U.S.C.
§ 841(c)(2); CAL. HEALTH & SAFETY CODE § 11100(a)(17) &
(e)(6).

   This case concerns the conviction of the proprietor of a
small pharmacy for selling cold remedies containing pseu-
doephedrine. Jae Gab Kim was convicted of violating 21
U.S.C. § 841(c)(2), which prohibits the distribution of listed
chemicals, including pseudoephedrine, “knowing, or having
reasonable cause to believe, that [the pseudoephedrine] will
be used to manufacture a controlled substance.” He argues
that, because drugs containing pseudoephedrine can be legally
sold over the counter and there is no bright line in the law
demarcating a legal sale from an illegal sale, the law allowing
conviction upon “reasonable cause to believe” is unconstitu-
tionally vague. We have previously held that § 841(c)(2) con-
tains a mens rea requirement. With that mens rea standard, the
statute is not unconstitutionally vague. We therefore affirm
Kim’s conviction.

                    I.   BACKGROUND

   Kim owned and operated the San Jacinto Pharmacy. After
receiving information about the law regarding the sale of
pseudoephedrine from an industry newsletter, Kim instructed
his clerk, Virginia Garcia, not to sell more than 150 sixty-
milligram pills per person, per day. Kim believed that sales
under this quantity were legal.
3926                    UNITED STATES v. KIM
   Kim purchased drugs containing pseudoephedrine from
Bergen Brunswig. In May 2000, the Drug Enforcement
Administration (DEA) received a report from Bergen Brun-
swig that Kim’s purchases of drugs containing pseudoephe-
drine had sharply increased.1

   The DEA began an investigation of Kim, sending under-
cover agents to purchase cold remedies containing pseu-
doephedrine from his pharmacy. Two transactions are
relevant to this appeal:2 On January 4, 2001, three undercover
agents entered Kim’s pharmacy. Kim was standing in an ele-
vated section at the rear of the pharmacy, filling prescriptions.
Kim nodded and smiled at the three agents. The agents
attempted to purchase all the packages of cold medication on
display. After Garcia started to tell the agents that one person
could not buy all the medication, Kim interjected to ask what
was going on and who was buying what. Kim instructed them
to return some of the medication so that his stock would not
be depleted. The three agents returned some of the boxes and
divided the remainder for purchase. Ultimately, the agents
were each allowed to purchase two boxes of 96-count thirty-
milligram tablets and one box of 24-count thirty-milligram
tablets, for a total of around 6 grams of pseudoephedrine.
Additionally, in Kim’s presence and conspicuously, the men
inquired about and purchased hydrogen peroxide, iodine, and
rubbing alcohol, all of which are used to manufacture
methamphetamine. One of the men mumbled, in connection
with the purchase of alcohol, that he needed alcohol to “break
it down.” One of the agents provided all the money for the
purchases, although the purchases were rung up separately.
  1
     Evidence at trial showed that Kim’s purchases increased from a total
of 347.28 grams in December 1999 to 1712.16 grams in April 2000. The
quantity continued to increase, reaching a high of 4396.32 grams in July
2000. Kim’s purchases of the larger-count bottles (stock bottles) also
increased drastically over the same time period.
   2
     There were seven total purchases by undercover agents, each one even-
tually resulting in a count in Kim’s indictment. As noted below, Kim was
ultimately convicted of only two counts in the indictment.
                        UNITED STATES v. KIM                       3927
There were confusing statements as to whether the person
who supplied the money was holding the others’ money for
them or, instead, paying for all the purchases himself.

   As Garcia was completing the transaction, one of the agents
asked, “Can we get some more of this tomorrow?” Garcia
answered, “Well hopefully.” Kim, however, answered,
“We’re not selling every day.” He added that the purchase
“lasts for you, normally.”

   The next day, January 5, 2001, the same three undercover
officers returned to the pharmacy. Kim again nodded to them
as they entered. Although the officers assumed that he recog-
nized them, there is no direct evidence that he did. One officer
attempted to purchase multiple bottles of pseudoephedrine.
Again, Garcia would not allow this sale to proceed. She did,
however, allow each man to purchase one 100-count sixty-
milligram bottle. As on the previous day, one officer held all
the money initially and handed it to the other two so they
could pay for their pseudoephedrine. Afterwards, the officers
also each purchased two 24-count boxes of thirty-milligram
pseudoephedrine, for a total of about 7.5 grams each. Kim
was not involved in this transaction, but he was in the store
at the time.

   Kim was indicted for violating 21 U.S.C. § 841(c)(2),3 for
distributing a listed chemical when the merchant “knows or
has reasonable cause to believe” that the chemical will be
used to manufacture illicit drugs.4 At trial, at the close of the
  3
     Unless otherwise noted, all references to the United States Code and
California Health and Safety Code are to the 2000 version.
   4
     Kim’s case previously came before the Ninth Circuit on appeal from
the dismissal of the indictment. United States v. Kim, 298 F.3d 746 (9th
Cir. 2002). Kim complained that his indictment could not stand because
it failed to allege that he knew that the pseudoephedrine he sold “would
be used to manufacture a drug outside the scope of his authority as a
licensed pharmacist.” Id. at 748. The district court agreed and dismissed
Kim’s indictment. The government appealed. Id. We reversed the district
court, determining that the elements of the crime were sufficiently set
forth to overcome a motion to dismiss. Id. at 750.
3928                      UNITED STATES v. KIM
government’s case-in-chief, the district court granted Kim’s
motion for judgment of acquittal on three counts. The jury
found Kim not guilty of another count. The district court later
granted a post-verdict judgment of acquittal as to yet another
count. In the end, Kim was convicted only on counts six and
seven, covering the incidents described above.

   Both after the government’s case-in-chief and after the jury
returned its verdict, Kim challenged the vagueness of the stat-
ute under which he was indicted. The district court denied
both motions. Kim was sentenced to five months incarcera-
tion, three years supervised release—during which he was to
spend five months in home detention—and a $15,000 fine.
We were informed at oral argument that he lost his pharma-
cist’s license as a result of the convictions.

               II.   STATE AND FEDERAL LAW

   [1] The federal statute under which Kim was convicted pro-
vides that “[a]ny person who knowingly or intentionally . . .
possesses or distributes a listed chemical knowing, or having
reasonable cause to believe, that the listed chemical will be
used to manufacture a controlled substance except as autho-
rized by this subchapter” shall be fined or imprisoned, or
both. 21 U.S.C. § 841(c)(2). The federal law also contains a
requirement that sales of certain packages of pseudoephedrine
be recorded.5 The recording statute contains a confusing maze
  5
   Certain of those sales that must be recorded must also be reported to
the government.
      Each regulated person shall report to the Attorney General . . .
      any regulated transaction involving an extraordinary quantity of
      a listed chemical, an uncommon method of payment or delivery,
      or any other circumstance that the regulated person believes may
      indicate that the listed chemical will be used in violation of this
      subchapter.
21 U.S.C. § 830(b)(1)(A). The statute contains no definition of “extraordi-
nary quantity.”
                         UNITED STATES v. KIM                         3929
of rules, exceptions to the rules, and exceptions to the excep-
tions. First, “[e]ach regulated person who engages in a regu-
lated transaction involving a listed chemical . . . shall keep a
record of the transaction for two years after the date of the
transaction.” 21 U.S.C. § 830(a)(1). Not all sales of listed
chemicals, however, are considered “regulated transactions.”
“[A]ny sale of ordinary over-the-counter pseudoephedrine . . .
by retail distributors shall not be a regulated transaction.”
§ 802(39)(A)(iv)(I)(aa). Over-the-counter sales of pseu-
doephedrine that are not “ordinary,” however, are regulated
transactions, because they are not included in the exemption
from “regulated transactions.” With respect to pseudoephe-
drine in particular,

      The term “ordinary over-the-counter pseudoephe-
      drine . . . product” means any product containing
      pseudoephedrine . . . sold in package sizes of not
      more than 3.0 grams of pseudoephedrine base . . .
      that is packaged in blister packs, each blister con-
      taining not more than two dosage units, or where the
      use of blister packs is technically infeasible, that is
      packaged in unit dose packets or pouches.

§ 802(45)(B)(i).6 Alternatively, sales of twenty-four grams or
more of pseudoephedrine are automatically subject to the
recording requirements of § 830. § 802(39)(A)(iv)(II). The
upshot is that over-the-counter sales of pseudoephedrine must
be recorded if the items purchased (1) were not in blister
packs; (2) were in packages of more than three grams per
package; or (3) totaled twenty-four grams or more.7
  6
     In the case of liquids, however, if they are “sold in package sizes of
not more than 3.0 grams of pseudoephedrine base,” they qualify as “ordi-
nary over-the-counter” sales. § 802(45)(B)(ii).
   7
     The federal law has very recently been amended. On March 9, 2006,
President Bush signed into law an amendment to the USA PATRIOT
Improvement and Reauthorization Act of 2005, which contained a section
entitled the Combat Methamphetamine Epidemic Act of 2005. Pub. L. No.
109-177, § 711, 120 Stat. 192, 256-63 (2006). The Combat Methamphet-
amine Epidemic Act strengthened the recording requirements of the fed-
eral statute and further restricted sales of pseudoephedrine. It contains no
amendment, however, to § 841(c)(2), the criminal liability section. See id.
3930                      UNITED STATES v. KIM
   California makes it a felony for people to sell certain sub-
stances “with knowledge or the intent that the recipient will
use the substance to unlawfully manufacture a controlled sub-
stance.” Cal. Health & Safety Code § 11104(a). The prohib-
ited substances, which include pseudoephedrine, are listed in
California Health and Safety Code section 11100(a), which
also requires merchants to report sales of regulated substances.8
The California reporting statute, section 11100, incorporates
federal law by exempting from its reporting requirements
those transactions involving chemicals “lawfully sold, trans-
ferred, or furnished over the counter without a prescription
pursuant to the federal Food, Drug, and Cosmetic Act (21
U.S.C. Sec. 301 et seq.) or regulations adopted thereunder.”
CAL. HEALTH & SAFETY CODE § 11100(e)(4)(A). The Califor-
nia statute, however, specifically does not exempt from its
reporting requirement sales “where the individual transaction
involves more than three packages or nine grams of” pseu-
doephedrine. Id. Thus, a pharmacist who sells more than nine
grams of pseudoephedrine must report the sale to the Califor-
nia government, whereas a pharmacist who sells less must
only report the sale to California if the drugs were sold in vio-
lation of the federal law—a category which would include, as
we have noted, sales made “knowing or having reasonable
cause to believe” that the purchase of drugs would be used to
manufacture methamphetamine.

  The upshot is that neither state nor federal law specifies any
“safe harbor” amount of pseudoephedrine that may be sold
over the counter. Instead, the seller’s actual or imputed
knowledge that the chemical will be used to manufacture
methamphetamine is determinative of criminal liability,
regardless of the amount sold.
  8
    “Any manufacturer, wholesaler, retailer, or other person in this state
who sells, transfers, or otherwise furnishes any of the following substances
to any person or business entity in this state or any other state shall submit
a report to the Department of Justice of all of those transactions . . . .” CAL.
HEALTH & SAFETY CODE § 11100(a).
                         UNITED STATES v. KIM                          3931
  A.    The Interaction Between Recording and Reporting
        Requirements and Criminal Liability

   Kim sold quantities below the per se reporting limits of the
California statute, never selling to the undercover DEA agents
more than three packages or nine grams of pseudoephedrine
during a single transaction. Kim argues that because the Cali-
fornia provision makes a sale of nine grams “otherwise autho-
rized,” he did not have adequate notice that a sale of less than
nine grams could subject him to federal prosecution.9 We
reject Kim’s claim.

   [2] First, Kim points to no support for his assumption that
the federal statute exempts from criminal liability transactions
permitted under state law. There is no provision in the federal
law providing a safe harbor for transactions “otherwise autho-
rized”; the term is entirely of Kim’s own construction. Fur-
thermore, unless a federal law states otherwise, state law
cannot empower a citizen to act contrary to a federal prohibi-
tion. See United States v. Moore, 109 F.3d 1456, 1462 (9th
Cir. 1997) (en banc).

   [3] Second, Kim appears to have confused the reporting
requirements under California law with the criminal liability
standards. The California provision does not “authorize[ ]”
single transactions of less than nine grams. As noted above,
the California law requires merchants to report to the Califor-
nia Department of Justice transactions involving sales of cer-
tain chemicals. A merchant need not report a lawful (under
federal law) sale of less than nine grams; he or she must report
  9
    Kim does not challenge the sufficiency of the evidence on his convic-
tion. In particular, he does not argue that because he did not directly par-
ticipate in the January 5 transaction, he could not be guilty of distributing
pseudoephedrine with any knowledge or reasonable cause to believe that
this particular sale would result in the production of methamphetamine.
We therefore do not decide whether a supervising pharmacist or proprietor
who does not participate directly in a specific transaction can be crimi-
nally liable under § 841(c)(2).
3932                     UNITED STATES v. KIM
a sale of more than nine grams, whether or not lawful under
federal law.10 The more-than-nine-grams standard is thus sig-
nificant for the purposes of California law only because it
delineates those sales that must automatically be reported
from those that may not need to be reported.

    [4] The California felony provision covering sales of pseu-
doephedrine, in contrast, contains no dosage safe harbor. Sec-
tion 11104(a), the criminal liability provision, makes it a
felony conviction to sell certain chemicals “with knowledge
or the intent” that those chemicals will be used to manufacture
illicit drugs. A sale of any quantity can violate California law
if it is entered into with the requisite mental state; the quantity
is irrelevant except as circumstantial evidence of intent.
Although Kim allowed the undercover agents to purchase
only quantities of pseudoephedrine below the per se reporting
requirement of the California statute, he was not necessarily
acting within the bounds of state law by consummating the
sale for those quantities.

   Kim argues that there is inadequate notice “of where (and
how) the line is drawn to indicate when an [over-the-counter]
sale that is otherwise authorized becomes one that is unlaw-
ful.” As noted above, however, Kim’s sales were not autho-
rized by the California statute, although they were not
explicitly prohibited either; the mens rea requirement was
determinative.

   Third, Kim’s arguments based solely on federal law fare no
better. He contends that because pseudoephedrine is legally
sold over-the-counter for personal use, he must have protec-
tion against criminal liability under federal law for those per-
sonal use sales that are below the level at which they must be
recorded. Pointing to provisions of federal law that mention
“legitimate medical use” and “personal use,” § 802(46)(A) &
  10
    Additionally, a merchant must report a sale that is unlawful under fed-
eral law.
                            UNITED STATES v. KIM                         3933
(B), Kim contends that “other than limiting the dosage level,
there is nothing in the law to provide a retail distributor with
assurance or guidance as to what is required for his over-the-
counter sales to be deemed sales for legitimate medical use.”

   Kim is correct that, under federal law, a retail distributor is
one who engages in sales for personal use, which are “below-
threshold” sales for legitimate medical purposes. 21 U.S.C.
§ 802(46).11 He forgets, however, that retail distributors are
only exempted from the definition of “regulated transaction”
(which triggers the recording requirements of § 830) when
they sell “not more than 3.0 grams of pseudoephedrine base
. . . that is packaged in blister packs, each blister containing
not more than two dosage units, or where the use of blister
packs is technically infeasible, that is packaged in unit dose
packets or pouches.” § 802(45)(B)(i).

   Kim is therefore correct that a bright-line rule exists estab-
lishing a threshold for sales of pseudoephedrine.12 This bright-
line rule, however, applies only to the recording requirements
and not to the criminal liability provision. The criminal liabil-
ity provision contains no cross-reference to the recording
requirements, nor does it include the terms “legitimate medi-
cal use” or “personal use.” Whether the over-the-counter sale
  11
    21 U.S.C. § 802(46) provides:
       (A) The term “retail distributor” means a grocery store, general
       merchandise store, drug store, or other entity or person whose
       activities as a distributor relating to pseudoephedrine or phenyl-
       propanolamine products are limited almost exclusively to sales
       for personal use, both in number of sales and volume of sales,
       either directly to walk-in customers or in face-to-face transactions
       by direct sales.
     (B) For purposes of this paragraph, sale for personal use means
     the sale of below-threshold quantities in a single transaction to an
     individual for legitimate medical use.
  12
     Kim’s sales to the undercover DEA agents do not fall within this
exception because they involved in part over-the-counter sales of stock
bottles, not solely blister packs.
3934                     UNITED STATES v. KIM
was for a legitimate medical purpose within the meaning of
the recording requirement is therefore technically irrelevant to
the criminal liability provision at issue here. In practical
terms, however, when a pharmacist knows or has reasonable
cause to believe that a below-threshold quantity of pseu-
doephedrine will be used for the production of methamphet-
amine, that is not a legitimate medical use.13

   [5] In any event, whether or not Kim had to report the sales
he entered into with the undercover DEA agents to the U.S.
Attorney General, he could still be subject to criminal prose-
cution if those sales violated § 841(c)(2). Kim’s criminal lia-
bility instead turns on whether he “kn[e]w or ha[d] reasonable
cause to believe” that his conduct would lead to manufacture
of illicit drugs. § 841(c)(2). As is true with other criminal stat-
utes, conduct is prohibited not solely because of its objective
contours, but because of the defendant’s state of mind regard-
ing such an effect. There is no quantity threshold exempting
a merchant from criminal liability under § 841(c)(2).

  B.    Vagueness and Mens Rea

   Kim argues that, construed as containing no quantity
threshold, the statute is unconstitutionally vague because it
does not provide a reasonably intelligent person with suffi-
cient notice concerning whether he is violating it. Essentially,
he argues that absent designation of a “safe harbor” amount
that he may sell to each individual each day, he cannot be
expected to conform his behavior to legal requirements and
thus avoid criminal liability. There is, however, no constitu-
  13
    In the prior appeal from the dismissal of Kim’s indictment, we deter-
mined that charging him with “reason to know that [the pseudoephedrine]
would be used to make methamphetamine” was sufficient to set forth the
elements of the crime. Kim, 298 F.3d at 750. Although a pharmacist is
authorized to sell pseudoephedrine for “legitimate medical use” under 21
U.S.C. § 802(46), if the pharmacist sells the pseudoephedrine in violation
of § 841(c)(2), his conduct is “not covered by the exception” of § 802(46).
Id.
                         UNITED STATES v. KIM                         3935
tional principle—and Kim points to none—requiring the fed-
eral government to spell out a specific amount of
pseudoephedrine that pharmacists may sell in each transaction
without incurring criminal liability. Nor do more general
vagueness principles support his contention.

   [6] “It is a basic principle of due process that an enactment
is void for vagueness if its prohibitions are not clearly
defined.” Grayned v. City of Rockford, 408 U.S. 104, 108
(1972). Vague laws that do not infringe upon First Amend-
ment rights have two principle evils:14 (1) they do not give a
“person of ordinary intelligence a reasonable opportunity to
know what is prohibited, so that he may act accordingly”; and
(2) they encourage arbitrary and discriminatory enforcement
by not providing explicit standards for policemen, judges, and
juries. Id. at 108-09; accord Kolender v. Lawson, 461 U.S.
352, 358 (1983). Thus, if a statute is not sufficiently clear to
provide guidance to citizens concerning how they can avoid
violating it and to provide authorities with principles govern-
ing enforcement, a defendant cannot be punished for violating
that statute.

   [7] Kim concedes, as he must, that vagueness challenges to
statutes that do not involve First Amendment violations must
be examined as applied to the defendant. See Vill. of Hoffman
Estates v. Flipside, Hoffman Estates, Inc., 455 U.S. 489, 495
n.7 (1982); see also United States v. Purdy, 264 F.3d 809, 811
(9th Cir. 2001) (“[O]ur concern is whether the [statute] is
impermissibly vague in the circumstances of this case.” (quot-
ing United States v. Ocegueda, 564 F.2d 1363, 1365 (9th Cir.
1977) (emphasis added))). Thus, if Kim’s actions clearly
come within the statute, he cannot make a void for vagueness
challenge. Ocegueda, 564 F.2d at 1365.
  14
    Vague laws that do implicate First Amendment rights also have the
“potential for arbitrarily suppressing First Amendment liberties.” Shuttles-
worth v. City of Birmingham, 382 U.S. 87, 91 (1965).
3936                      UNITED STATES v. KIM
  Kim suggests that an as-applied vagueness challenge
requires only that the defendant show that his conduct, as
proven at trial, was not clearly prohibited by the statute. This
approach would, in essence, raise the usual sufficiency of the
evidence standard to something akin to a clear and convincing
evidence standard if a vagueness challenge is raised.

   Kim seriously misinterprets the vagueness doctrine. The
inquiry into whether Kim’s conduct clearly falls within the
statute is only a threshold inquiry, weeding out those defen-
dants who cannot make an as-applied vagueness challenge at
all. If, as here, the defendant’s conduct does not fall squarely
and obviously within the statute, he can make an as-applied
vagueness challenge. But when the jury finds, on sufficient
evidence, that he committed the statutory offense, the defen-
dant must still demonstrate that the statute is unconstitution-
ally vague as applied to him to avoid conviction.15 See Purdy,
264 F.3d at 811 (examining the vagueness of the statute as
applied to the defendant).

   [8] We have previously held that § 841(c)(2) contains a
mens rea requirement. United States v. Johal, 428 F.3d 823,
827 (9th Cir. 2005). The statute “requires that a defendant
subjectively know facts that either cause him or would cause
a reasonable person to believe that the ingredients are being
used to produce illegal drugs.” Id. Whether a defendant is
guilty of having “reasonable cause to believe” that the pseu-
doephedrine will be used to produce illicit drugs “turns on the
facts actually known by the defendant in a particular case.” Id.
at 828. Also, the requirement includes the specification that
the defendant had reasonable cause to believe that the chemi-
cal he sold “will be used to manufacture a controlled sub-
stance,” § 841(c)(2) (emphasis added); mere probability of
use is insufficient.16 For all these reasons, the statutory “rea-
   15
      As we noted earlier, we are assuming sufficient evidence because suf-
ficiency was not challenged.
   16
      Johal rejected the defendant’s contention that the “statute requires the
actual production of methamphetamine. Johal, 428 F.3d at 828. It is there-
                        UNITED STATES v. KIM                        3937
sonable cause to believe” mens rea standard “limits the likeli-
hood that a defendant will be prosecuted for mere inadvertent
conduct and is consistent with the longstanding principle pre-
suming a mens rea requirement for criminal activity.” Johal,
428 F.3d at 827.

  [9] The holding in Johal forecasts our decision here,
because “a scienter requirement may mitigate a law’s vague-
ness, especially with respect to the adequacy of notice to the
complainant that his conduct is proscribed.” Vill. of Hoffman
Estates, 455 U.S. at 499. Significantly, here, a person of ordi-
nary intelligence can base his behavior on his factual knowl-
edge of the situation at hand and thereby avoid violating the
law.

   “[R]easonable cause to believe” or similar language is
found in other statutes. See Stoianoff v. Montana, 695 F.2d
1214, 1221-22 & n.5 (9th Cir. 1983) (regarding “reasonably
should know”); see also United States v. Saffo, 227 F.3d
1260, 1268 (10th Cir. 2000) (regarding “reasonable cause to
believe”); United States v. Biro, 143 F.3d 1421, 1430 (11th
Cir. 1998) (regarding “reason to know”). These statutes have
“repeatedly withstood vagueness challenges.” Wash. Mercan-
tile Assoc. v. Williams, 733 F.2d 687, 692 (9th Cir. 1984).
“[T]he fact that a defendant reasonably should have known
something is established in substantially the same manner as
actual knowledge.” Stoianoff, 695 F.2d at 1221.
“[R]easonable cause to believe” is therefore substantially sim-
ilar to knowledge in eliminating vagueness. It is often proven
largely through circumstantial evidence and inferences, but
what must be proven is not vague.

fore of no consequence that Kim sold the pseudoephedrine to undercover
federal agents who presumably did not actually manufacture illicit drugs
with their purchases. The key question is whether Kim had “reasonable
cause to believe the chemical will be used to make drugs.” Id. The inquiry
therefore centers on defendant’s understanding, or imputed understanding,
of the situation at the time of the sale.
3938                 UNITED STATES v. KIM
   Kim argues that larger chain stores escape liability because
of their larger size and mechanized checkouts, demonstrating
that the statute is subject to arbitrary enforcement and there-
fore vague. We do not have any evidence on the record sup-
porting Kim’s differential enforcement accusation. Even
assuming that it is accurate, however, lack of prosecution of
some cases that could be covered by a statute “is no sufficient
reason to hold the language too ambiguous to define a crimi-
nal offense.” United States v. Petrillo, 332 U.S. 1, 7 (1947).

   Furthermore, any discrepancy in enforcement could well be
the result of a structural difference between the chain stores
and small pharmacies, rather than of arbitrary enforcement. It
is not that the statute has no guidelines, such that the authori-
ties can arbitrarily prosecute one class of merchants instead of
another, but rather that the statute allows for a situation in
which a store’s structure can, intentionally or not, cause its
employees and managers to avoid criminal liability. The dis-
incentive to prosecute may be a matter of proof—that it is dif-
ficult for the government to prove the existence of an actor in
the chain stores who knows or has reasonable cause to believe
that a sale of pseudoephedrine will lead to the manufacture of
methamphetamine, because checkout stands are covered by
many different people at different times or not covered at all.
Alternatively, the reason for any discrepancy in prosecution
may be a matter of there not being an actor in the store who
has such mens rea, because the larger stores have ways of
monitoring their sales to assure that suspicious sales do not
occur. Or it may be that the smaller, nonchain stores are tar-
geted by the methamphetamine manufacturers themselves and
so are more likely to come on the DEA’s radar screen through
pseudoephedrine manufacturers’ reports or personal observa-
tion. As these examples show, given the reach of prosecu-
torial discretion, there are many explanations for differential
prosecution—not all of them indicative of the most efficient
policy—other than the vagueness of the statute involved.
                          UNITED STATES v. KIM                            3939
                         III.   CONCLUSION

   Kim has misinterpreted, whether deliberately or not, his
obligations under the federal and state laws restricting the sale
of pseudoephedrine. We clarify here that the recording and
reporting statutes establish no safe harbor from prosecution
under § 841(c)(2). Instead, retailers must refrain from selling
any amount of pseudoephedrine knowing or having reason-
able cause to believe that the buyer intends to use the chemi-
cal to manufacture methamphetamine. Here, the jury
determined that Kim knew or had reasonable cause to believe
that the sales to the undercover DEA agents would lead to the
manufacture of methamphetamine. Kim apparently thought he
could rely on some magic formula, rather than his own
informed observation of his customers, to decide which sales
were legal and which were not. Congress has chosen not to
provide such a formula. Balancing its desire to continue to
allow sales of cold medicines without a prescription against
the apparent propensity of methamphetamine manufacturers
to accumulate chemicals for their manufacturing processes
through purchases from ordinary retail stores, Congress has
placed responsibility to monitor pseudoephedrine sales on
those who are profiting from them.

   There may be circumstances more marginal than this one
in which that approach could yield an unfair result. Careful
attention to the sufficiency of the evidence in cases under
§ 841(c)(2) is therefore of critical importance, so as not to dis-
suade legitimate retailers from selling these useful home rem-
edies at all, for fear of prosecution.17 That Kim was acquitted
   17
      Although he did not raise a sufficiency argument, Kim’s case is some-
what close compared to others that have been reported. See, e.g., Johal,
428 F.3d at 825-26; Saffo, 227 F.3d at 1263-66. There was, however suffi-
cient evidence supporting the jury’s conclusion, at least to the January 4
offense: Before the sting operation, Kim was warned by investigators from
the California Pharmacy Board about the dangers of pseudoephedrine and
his potential liability. There was a large spike in his sales, especially of the
3940                    UNITED STATES v. KIM
by the judge and the jury on most of the counts against him
indicates that such care was taken in this case.

   [10] In sum, we conclude that because it has a sufficiently
clear mens rea provision, § 841(c)(2) is not unconstitutionally
vague. Kim’s conviction was therefore valid.

  AFFIRMED.




larger stock bottles. On January 4, Kim directly encountered three men
who were acting suspiciously while purchasing substantial quantities of
pseudoephedrine—specifically, stating a desire to “break it down”; pur-
chasing alcohol, hydrogen peroxide, and iodine; attempting to purchase
the entire supply of pseudoephedrine packages; and paying through a sin-
gle person, suggesting one transaction rather than three—and yet he
allowed the sale to proceed.
