FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA,                       No. 07-10254
                Plaintiff-Appellee,                D.C. No.
               v.
                                               CR-00-00049-JSU
MI KYUNG BYUN, aka Mi Kyung                      ORDER AND
Mechanic,                                         AMENDED
             Defendant-Appellant.
                                                  OPINION

         Appeal from the District Court of Guam
  Francis M. Tydingco-Gatewood, Chief Judge, Presiding

                  Argued and Submitted
       September 26, 2007—San Francisco, California

                       Filed July 1, 2008
                    Amended August 14, 2008

       Before: John R. Gibson,* Marsha S. Berzon, and
                Carlos T. Bea, Circuit Judges.

                    Opinion by Judge Berzon




   *The Honorable John R. Gibson, Senior United States Circuit Judge for
the Eighth Circuit, sitting by designation.

                                10617
10622               UNITED STATES v. BYUN


                         COUNSEL

Howard Trapp, Hagatna, Guam, for the defendant-appellant.

Kevin R. Gingras, Washington, D.C., for plaintiff-appellee
Department of Justice.


                          ORDER

The mandate issued on July 24, 2008, is recalled. The opinion
filed on July 1, 2008, slip op. at 7929, is amended as follows:
                     UNITED STATES v. BYUN                 10623
Slip op. at 7929, caption: Change  to
                           .

Slip op. at 7929, caption: Change  to .

No further petitions shall be entertained. The mandate shall
issue forthwith.


                          OPINION

BERZON, Circuit Judge:

   After Mi Kyung Byun pleaded guilty to a violation of 8
U.S.C. § 1328, “importation into the United States of any
alien for the purpose of prostitution,” the district court deter-
mined that she had committed a “sex offense” within the
meaning of Section 111 of Title I of the Adam Walsh Child
Protection and Safety Act of 2006 (“Act” or “Walsh Act”),
Pub. L. No. 109-248, 120 Stat. 587, 591 (codified at 42
U.S.C. § 16911), and is therefore subject to the Act’s registra-
tion requirements. Byun appeals that determination, maintain-
ing that her offense is not covered by the Act. We conclude
that Byun’s offense is a “specified offense against a minor”
and therefore a “sex offense” within the meaning of the Act.

                               I.

   Mi Kyung Byun and her husband owned and operated a
night club in Guam, Club Azabu. At the club, Byun main-
tained two rooms in which female employees could engage in
sexual acts with the club’s clients. Byun also arranged for her
female staff members to leave the club with clients and have
sex with them for a fee.
10624                   UNITED STATES v. BYUN
   Byun was indicted on May 31, 2000 on four counts of alien
smuggling, including one count of importing aliens into the
United States for purposes of prostitution, in violation of 8
U.S.C. § 1328, and one count of transporting a minor in for-
eign commerce with the intent that the minor engage in prosti-
tution, in violation of 18 U.S.C. § 2423(a). She ultimately
pleaded guilty to three counts of alien smuggling in violation
of 8 U.S.C. §§ 1324 and 1328, but did not plead guilty to
transporting a minor for purposes of prostitution in viola-
tion of 18 U.S.C. § 2423(a). In the plea agreement, Byun
admitted that she “induced” Youn Be Seo, a citizen of Korea,
“to come to Guam by offering to employ [her] at the Club . . .
intend[ing] that during the course of [her] employment at the
Club . . . [she] would engage in sexual contact with the Club’s
customers, and perform sexual acts for money,” and acknowl-
edged that “[a]t the time [Byun] solicited Youn Be Seo to
come to Guam, and at all times thereafter, [Byun] knew Seo
was seventeen years old.” At sentencing, the district court
sentenced Byun to fifteen months imprisonment and three
years of supervised release.

   On July 27, 2006, while Byun was on supervised release,
Congress passed the Walsh Act. Title I of the Walsh Act, the
Sex Offender Registration and Notification Act (“SORNA”),
requires every jurisdiction in the United States to maintain a
sex offender registry that complies with SORNA’s specifica-
tions. 42 U.S.C. § 16912.1 SORNA defines the terms “sex
offenders,” and “sex offense,” mandates that sex offenders
register, and divides sex offenders into “tiers,” based on the
severity of their crime, which determine the details of the reg-
istration requirement. § 16911.

  In response to the Walsh Act, Byun’s probation officer
determined that Byun was a tier II sex offender subject to
SORNA’s registration requirements and provided her an “of-
  1
   All statutory citations are to Title 42 of the United States Code unless
otherwise indicated.
                       UNITED STATES v. BYUN                       10625
fender notice and acknowledgment of duty to register as a sex
offender.” Byun signed the form and registered with the Sex
Offender Registry Office the same day. Nine days later she
filed a motion requesting that the district court “vacat[e] and
set[ ] aside the determination” of the probation officer,
because she “has never been convicted of a sex offense.”

   The district court denied the motion, holding that Byun had
been convicted of a “sex offense” within the meaning of
SORNA, is therefore a “sex offender,” and is properly classi-
fied as a “tier II sex offender.” Byun appeals the determina-
tion that she is a sex offender for purposes of SORNA.

                                   II.

   [1] The Sex Offender Registration and Notification provi-
sions of the Walsh Act are intended to “establish[ ] a compre-
hensive national system for the registration” of “sex offenders
and offenders against children.” § 16901. Section 111 of
SORNA identifies those individuals who are subject to the
registration requirement. According to section 111, a “sex
offender” is “an individual who was convicted of a sex
offense.” § 16911(1). A sex offense, in turn, is:

      (i) a criminal offense that has an element involving
      a sexual act or sexual contact with another; [or]

      (ii) a criminal offense that is a specified offense
      against a minor . . . .2

§ 16911(5)(A). “Specified offense against a minor” is defined
in a separate provision:
  2
   SORNA also includes in the definition of sex offenses certain specified
federal crimes not relevant here, § 16911(5)(A)(iii); certain military
offenses, § 16911(5)(A)(iv); and an attempt or conspiracy to commit any
sex offense, § 16911(5)(A)(v).
10626               UNITED STATES v. BYUN
    (7) Expansion of definition of “specified offense
    against a minor” to include all offenses by child
    predators

    The term “specified offense against a minor” means
    an offense against a minor that involves any of the
    following:

         (A) An offense (unless committed by a par-
         ent or guardian) involving kidnapping.

         (B) An offense (unless committed by a par-
         ent or guardian) involving false imprison-
         ment.

         (C) Solicitation to engage in sexual con-
         duct.

         (D) Use in a sexual performance.

         (E) Solicitation to practice prostitution.

         (F) Video voyeurism as described in [18
         U.S.C. § 1801].

         (G) Possession, production, or distribution
         of child pornography.

         (H) Criminal sexual conduct involving a
         minor, or the use of the Internet to facilitate
         or attempt such conduct.

         (I) Any conduct that by its nature is a sex
         offense against a minor.

§ 16911(7).

   [2] Section 111 goes on to divide sex offenders into three
“tiers,” depending on the nature of their offense. Tier II sex
                          UNITED STATES v. BYUN                           10627
offenders — the category that, according to the district court,
includes Byun — are, as here pertinent, those

      whose offense is punishable by imprisonment for
      more than 1 year and—

      (A) [whose offense] is comparable to or more
      severe than the following offenses, when committed
      against a minor, or an attempt or conspiracy to com-
      mit such an offense against a minor:

            (i) sex trafficking (as described in [18
            U.S.C. § 15913]);

            (ii) coercion and enticement (as described
            in [18 U.S.C. § 2422(b)4]);

            (iii) transportation with intent to engage in
            criminal sexual activity (as described in [18
            U.S.C. § 2423(a)5]);
  3
      18 U.S.C. § 1591 provides, in relevant part, that “[w]hoever knowingly
. . . in or affecting interstate or foreign commerce . . . recruits, entices, har-
bors, transports, provides, or obtains by any means a person . . . knowing
that . . . the person has not attained the age of 18 years and will be caused
to engage in a commercial sex act, shall be punished . . . .” 

    4
      18 U.S.C. § 2422(b) provides that:
       Whoever, using the mail or any facility or means of interstate or
       foreign commerce, . . . knowingly persuades, induces, entices, or
       coerces any individual who has not attained the age of 18 years,
       to engage in prostitution or any sexual activity for which any per-
       son can be charged with a criminal offense, or attempts to do so,
       shall be fined under this title and imprisoned not less than 10
       years or for life.
    5
      18 U.S.C. § 2423(a) provides:
       Transportation with intent to engage in criminal sexual
       activity.—A person who knowingly transports an individual who
       has not attained the age of 18 years in interstate or foreign com-
       merce, or in any commonwealth, territory, or possession of the
       United States, with the intent that the individual engage in prosti-
       tution, or in any sexual activity for which any person can be
       charged with a criminal offense, shall be fined under this title and
       imprisoned not less than 10 years or for life.
10628                 UNITED STATES v. BYUN
          (iv) abusive sexual contact (as described in
          [18 U.S.C. § 2244]); [or]

    (B)    involves—

          (i) use of a minor in a sexual performance;

          (ii) solicitation of a minor to practice prosti-
          tution; or

          (iii) production or distribution of child por-
          nography; . . .

§ 16911(3).

    [3] Sex offenders must “register, and keep the registration
current, in each jurisdiction where the offender resides, where
the offender is an employee, and where the offender is a stu-
dent.” § 16913(a). To keep her registration current, an
offender must, “after each change of name, residence,
employment, or student status,” appear in person in one of the
jurisdictions in which she is required to register and notify it
of the changed information. § 16913(c). In addition, all sex
offenders are required to “appear in person” at regular inter-
vals: “each year, if the offender is a tier I sex offender; . . .
every six months, if the offender is a tier II sex offender; and
. . . every 3 months, if the offender is a tier III sex offender.”
§ 16916. The duration of the registration requirement varies
depending on the tier of the sex offender: tier I sex offenders
must comply with the registration requirements for a period
of 15 years; tier II sex offenders, for a period of 25 years; and
tier III sex offenders, for life. § 16915(a).

  [4] The consequences of failing to comply with SORNA’s
registration requirements are significant. A sex offender may
be imprisoned for up to ten years for knowing failure to com-
ply with SORNA’s requirements, and an individual convicted
of a crime of violence after failing to comply with the regis-
                         UNITED STATES v. BYUN                        10629
tration requirements is subject to a mandatory minimum five-
year term of imprisonment. 18 U.S.C. § 2250(a), (c).

                                    III.

   The question before us is whether Byun’s conviction for
importation of an alien for purposes of prostitution, 8 U.S.C.
§ 1328, makes her a “sex offender” for purposes of SORNA
and thus subject to its registration requirements.6 We conclude
that Byun’s conviction under 8 U.S.C. § 1328 — which her
plea agreement reveals was committed against a minor — is
a “specified offense against a minor” and therefore a sex
offense. § 16911(7)(I).

                                     A.

  Byun was convicted of a violation of 8 U.S.C. § 1328,
which provides, in relevant part, that:
  6
    This is a question of first impression in this circuit. Although there are
a number of district court decisions in other circuits regarding SORNA,
they address retroactivity issues and constitutional challenges based on the
Ex Post Facto Clause, the non-delegation doctrine, the Commerce Clause,
and the Due Process Clause, not the appropriate interpretation of the “sex
offender” definition. See, e.g., United States v. Madera, 

(M.D. Fla. 2007) (retroactivity, nondelegation doctrine, Ex Post
Facto, Due Process, and Commerce Clauses), rev’d, No. 07-12176, 

(11th Cir. May 23, 2008) (reversing district court’s retroac-
tivity determination); United States v. Mason, 

(M.D.
Fla. 2007) (retroactivity, nondelegation doctrine, Ex Post Facto, Due Pro-
cess, and Commerce Clauses); United States v. Templeton, No. CR-06-
291, 

(W.D. Okla. Feb. 7, 2007) (retroactivity, Ex Post
Facto, Due Process, and Commerce Clauses); United States v. Kapp, 

(M.D. Pa. 2007) (retroactivity); United States v. Roberts,
No. 07-70031, 

(W.D. Va. July 27, 2007) (retroactiv-
ity); United States v. Hinen, 

(W.D. Va. 2007) (retro-
activity, nondelegation, Due Process, Equal Protection, and Commerce
Clauses). Byun has not raised a challenge to the retroactivity or constitu-
tionality of SORNA.
10630                   UNITED STATES v. BYUN
      [t]he importation into the United States of any alien
      for the purposes of prostitution, or for any other
      immoral purpose, is forbidden. Whoever shall,
      directly or indirectly, import, or attempt to import
      into the United States any alien for the purpose of
      prostitution or for any other immoral purpose, or
      shall hold or attempt to hold any alien for any such
      purpose in pursuance of such illegal importation, or
      shall keep, maintain, control, support, employ, or
      harbor in any house or other place, for the purpose
      of prostitution or for any other immoral purpose, any
      alien, in pursuance of such illegal importation, shall
      be fined under Title 18, or imprisoned not more than
      10 years, or both.

Thus, at a minimum, conviction under the applicable provi-
sions of 8 U.S.C. § 1328 requires proof that (1) defendant
imported a person into the United States; (2) that person was
an alien; and (3) defendant imported the alien for the purpose
of having him or her engage in prostitution or for some other
immoral purpose.7

   We assume for purposes of our initial analysis, in Part
III.A, that we may consider the fact that Byun’s crime was
committed against a minor, even though the age of the victim
was not an element of her crime of conviction. Having deter-
mined that, assuming the age of Byun’s victim is taken into
account, her crime was a sex offense, we then consider in Part
III.B whether the statute might instead require a categorical
approach to the age of the victim of the crime, and conclude
that it does not.
  7
   Although the statute allows conviction both for importation for the pur-
pose of prostitution and for importation for some other immoral purpose,
we conclude, for purposes of our analysis, that Byun was convicted of
importation for the purpose of prostitution, as the charging documents so
indicate.
                         UNITED STATES v. BYUN                         10631
   [5] Under SORNA, Byun qualifies as a “sex offender” if
she was convicted of a “sex offense.” § 16911(1). A “sex
offense” is defined as either “a criminal offense that has an
element involving a sexual act or sexual contact with anoth-
er,” § 16911(5)(A)(i), or “a criminal offense that is a specified
offense against a minor,” § 16911(5)(A)(ii). Byun’s offense
entailed the importation of a seventeen-year-old woman into
Guam with the intent that she engage in sexual contact with
customers in Byun’s club. We conclude this offense was a
“specified offense against a minor,” and thus qualifies as a
sex offense under § 16911(5)(A)(ii). Because we hold Byun
committed a sex offense under § 16911(5)(A)(ii), we do not
address whether Byun’s crime qualifies as a sex offense under
§ 16911(5)(A)(i) (“a criminal offense that has an element
involving a sexual act or sexual contact with another”).8
  8
    In her brief, Byun primarily argues that her offense is not one having
an “element involving a sexual act or sexual contact with another” because
it does not require that any individual actually engage in a sexual act.
Many of the specified offenses against a minor, however, do not require
that any person engage in a sexual act. See § 16911(7)(A)-(G). As we ulti-
mately conclude that Byun’s offense is a specified offense against a minor,
we need not determine whether offenses having an “element involving a
sexual act or sexual contact with another” include those in which only an
intent that a sexual act occur is required, not the act itself.
   We recognize that the government contended to the district court only
that Byun was a sex offender under § 16911(5)(A)(i); the government did
not assert Byun was a sex offender under § 16911(5)(A)(ii). Although we
do not, as a general rule, “consider issues not passed upon below,” this
court has discretion to consider an issue not raised to the trial court when
it is “purely one of law and either does not affect or rely upon the factual
record developed by the parties . . . or the pertinent record has been fully
developed.” United States v. Patrin, 

, 712 (9th Cir. 1978).
Whether Byun qualifies as a sex offender under § 16911(5)(A)(ii) is
purely an issue of law, and the only facts relevant to this inquiry are the
undisputed facts admitted by Byun in her plea agreement. Further, Byun
is not prejudiced by our consideration of this question, which she specifi-
cally addressed in her briefs both to the district court and to this court, and
which was discussed during oral argument. See 

.
Thus, we exercise our discretion to consider whether Byun qualifies as a
sex offender under § 16911(5)(A)(ii), and we hold that she does.
10632                UNITED STATES v. BYUN
   [6] Turning to the list of “specified offense[s] against a
minor,” we find that the crime of which Byun was convicted
does not neatly correspond to any of the listed “specified
offenses.” In particular, whether Byun was convicted of or
admitted to “[s]olicitation to practice prostitution,”
§ 16911(7)(E), the most likely listed crime, is not clear. Solic-
itation is generally defined as “[t]he criminal offense of urg-
ing, advising, commanding, or otherwise inciting another to
commit a crime.” BLACK’S LAW DICTIONARY (8th ed. 2004).
None of the offenses of which Byun was convicted had solici-
tation as an element.

   Even assuming that we can look to the underlying facts of
Byun’s crime, Byun’s plea agreement does not conclusively
establish that she solicited Seo to practice prostitution. The
plea agreement states that “[b]etween January and March 31,
2000, defendant encouraged and induced Youn Be Seo . . . to
come to Guam by offering to employ [her] at the Club” and
that Byun “intended that . . . [Seo] would engage in sexual
contact with the Club’s customers, and perform sexual acts
for money.” The plea agreement makes clear that Byun
induced Seo to come to the United States by offering her
employment of some kind in her club, and that Byun intended
that Seo would engage in prostitution once she arrived. But
the plea agreement never explicitly states that Byun solicited,
urged, advised, or otherwise incited Seo to engage in prostitu-
tion. It seems likely from the circumstances that such solicita-
tion of Seo eventually occurred, but that fact was not
explicitly admitted in the plea agreement. We thus cannot
find, on the basis of the record, that Byun solicited a minor
to practice prostitution.

   [7] This determination is not, however, the end of the story.
The category of “specified offense[s] against a minor” also
includes a catchall provision for “conduct that by its nature is
a sex offense against a minor.” For two reasons, we conclude
that Byun’s offense likely falls within this category. First, the
strong similarity of Byun’s offense to at least one of the listed
                        UNITED STATES v. BYUN                        10633
offenses, i.e., solicitation of a minor to practice prostitution,
supports a conclusion that the catchall provision includes
Byun’s crime. See Gutierrez v. Ada, 

, 255 (2000)
(“[A] word is known by the company it keeps.” (alteration in
original) (quoting Gustafson v. Alloyd Co., 

, 575
(1995)); Washington State Dept. of Social and Health Servs.
v. Guardianship Estate of Keffeler, 

, 384 (2003)
(noting that “[w]here general words follow specific words in
a statutory enumeration, the general words are construed to
embrace only objects similar in nature to those objects enu-
merated by the preceding specific words”) (alteration in origi-
nal) (quoting Circuit City Stores, Inc. v. Adams, 

,
114-15 (2001)). As a common sense matter, transporting a
minor to the United States with the intent that she engage in
prostitution is no less “conduct that by its nature is a sex
offense against a minor” than is soliciting a minor to the same
end. The “transportation with intent” conduct in which Byun
engaged was almost certain to end in Byun urging, advising,
commanding, or otherwise inciting Seo to practice prostitu-
tion, unless Byun was deflected from carrying out her intent.
Moreover, neither the transportation nor the solicitation
crimes require that any prostitution actually occur, but both
may well result in prostitution by a minor. The catchall “spec-
ified offense” category therefore likely includes crimes such
as Byun’s.

   [8] Second, Byun’s offense appears to be a “tier II” sex
offense within the meaning of the statute, a circumstance that
supports the conclusions both that it must be a “sex offense”
of some kind, and, more specifically, that it is a “specified
offense against a minor.” The tier II sex offender category
provides significant guidance in determining whether Con-
gress intended that certain crimes be treated as sex offenses
under SORNA.9 Because an individual must be a sex offender
  9
    Byun argues, correctly, that the “tier II” category does not provide the
definition of a “sex offense”; that definition is contained in 16911(5).
Nonetheless, the definition of “sex offense” is appropriately interpreted in
the context of the statute as a whole, and the “tier II” category sheds sig-
nificant light on the “sex offense” definition.
10634                   UNITED STATES v. BYUN
before she can be a “tier II sex offender,” it follows that Con-
gress must have determined that those crimes listed in
§ 16911(3) (defining tier II offenses) were themselves “sex
offenses.”

   [9] The tier II definition indicates that individuals whose
“offense” is one of the listed crimes, or a crime “comparable
to or more severe than” them, when committed against a
minor, are tier II sex offenders. One of the listed offenses in
the tier II sex offender category, 18 U.S.C. § 2423(a), forbids
knowingly transporting a minor in interstate or foreign com-
merce with the intent that the minor engage in prostitution. 

of which Byun was convicted, 8 U.S.C. § 1328,
contains all of the elements of 18 U.S.C. § 2423(a), with the
exception of the requirement that the victim be a minor.10
Moreover, Byun’s offense also seems to parallel, but for
absence of the “minor” element, 18 U.S.C. § 1591, a tier II
offense which makes criminal knowingly “transport[ing]” an
individual in interstate or foreign commerce with knowledge
“that the person has not attained the age of 18 years and will
  10
     8 U.S.C. § 1328 prohibits “directly or indirectly . . . import[ing]” an
individual for purposes of prostitution, while 18 U.S.C. § 2423(a) prohib-
its “knowingly transport[ing]” a minor in interstate or foreign commerce
for such purpose. Although the language of these two elements is some-
what different, it is clear from our case law that Byun was convicted of
a crime with an element of “knowingly transporting” for purposes of 18
U.S.C. § 2423(a). We have held that evidence of an intent to import for
purposes of prostitution is necessary for a conviction under 18 U.S.C.
§ 1328, so no conviction can be had under that statute without proving that
the defendant knew she was transporting an individual in interstate com-
merce. See United States v. Gracidas-Ulibarry, 

, 1194 n.8
(9th Cir. 2000) (en banc) (citing Pena-Cabanillas v. United States, 

, 789 n.4 (9th Cir. 1968)). Moreover, a conviction for violation
of 18 U.S.C. § 2423(a) does not require that the defendant personally (or
“directly”) transport the victim: “knowing[ ] transport[ation]” occurs when
a defendant “causes the transport of” a minor for purposes of prostitution.
United States v. Johnson, 

, 1285 (9th Cir. 1997) (rejecting
the argument that a defendant who had arranged with a foreign exchange
program to have a Norwegian teenager travel to his home in California
had not “knowingly transport[ed]” him).
                        UNITED STATES v. BYUN                        10635
be caused to engage in a commercial sex act.” 18 U.S.C.
§ 1591(a). Assuming, as we have for this part of our analysis,
that we may consider that Byun’s victim was a minor, Byun’s
offense is “comparable to or more severe than” the listed tier
II offenses under § 2423(a) and 1591(a) and therefore falls
within the category of tier II offenses.

   That Byun’s offense is comparable to a listed tier II offense
supports not only the general conclusion that her crime is a
“sex offense,” but that it is, more particularly, a “specified
offense against a minor.” In general, the list of tier II sex
offenses closely corresponds to the list of “specified offen-
se[s] against a minor” in § 16911(7). Nearly all of the listed
offenses in tier II necessarily involve minor victims, and
many overlap significantly with the specified offenses against
a minor.11 For example, tier II offenses include “coercion and
enticement” of a minor to engage in prostitution (18 U.S.C.
§ 2422(b)), § 16911(3)(A)(ii); “use of a minor in a sexual per-
formance,” § 16911(3)(B)(i); and “production or distribution
of child pornography,” § 16911(3)(B)(iii). As the tier II list —
which, as noted, appears to include Byun’s offense — informs
our interpretation of “specified offense[s] against a minor,”
we are convinced that the offenses against minors listed as tier
II crimes either correspond directly to one of the spelled-out
“specified offense[s] against a minor” listed in § 16911(7) or
are included in the catchall category of “conduct that by its
nature is a sex offense against a minor.” Thus, if we may con-
sider the fact that Byun’s offense was in fact against a minor,
her crime qualifies as a specified offense against a minor
under the catchall category of “conduct that by its nature is a
sex offense against a minor.”
  11
     Tier II also includes offenses that “occur[ ] after the offender becomes
a tier I sex offender.” § 16911(3)(C).
10636               UNITED STATES v. BYUN
                              B.

   [10] We have assumed to this point that we may consider
the fact that Byun committed her crime against a minor. The
crime of which Byun was convicted, however, violation of 8
U.S.C. § 1328, does not have as an element that the victim
was a minor. Our determination that Byun committed a “spec-
ified offense against a minor,” as well as that her offense is
a tier II sex offense, thus depends on an examination of the
underlying facts of Byun’s crime, which reveal that one of
Byun’s victims was only 17 years old. See § 16911(3)(A) (an
offense is a tier II offense when, among other things, it is
“committed against a minor”). Consequently, before we may
finally conclude that Byun is a sex offender, we must consider
whether the statute permits examination of the underlying fact
of the age of Byun’s victim, or rather requires a “categorical”
approach as to that circumstance.

   [11] In the contexts of immigration law and of the enhance-
ment of criminal sentences, courts usually apply a categorical,
or modified categorical, approach to determine whether the
crime of which the defendant was convicted meets the statu-
tory requirements to have immigration consequences or pro-
vides the basis for a sentencing enhancement, rather than
allowing examination of the underlying facts of an individu-
al’s crime. See, e.g., Taylor v. United States, 

,
602 (1990) (concluding that a categorical or a modified cate-
gorical, rather than a “factual approach,” was required to
determine whether the defendant had committed “burglary”
for purposes of sentence enhancement); Li v. Ashcroft, 

, 895-96 (9th Cir. 2004) (holding that to determine
whether a crime of conviction is an aggravated felony, the
court makes a categorical comparison between the generic
crime and the crime of which the person has been convicted);
see also United States v. Rodriguez-Guzman, 

,
746-47 (9th Cir. 2007) (applying modified categorical
approach, which permits examination of the record of convic-
tion, in Sentencing Guidelines case because “the statute of
                     UNITED STATES v. BYUN                 10637
conviction is overly inclusive”). But cf. United States v.
Belless, 

, 1065-67 (9th Cir. 2003) (holding that
for purposes of conviction under 18 U.S.C. § 922(g)(9) —
possession of a firearm by one “who has been convicted in
any court of a misdemeanor crime of domestic violence” —
the earlier crime of conviction need not have as an element
that the victim had a domestic relationship to the perpetrator);
Tokatly v. Ashcroft, 

, 622 (9th Cir. 2004) (stating
that the categorical approach is not applied in the immigration
context when Congress has specifically made conduct, rather
than conviction, the basis for removal).

   In Taylor, the Supreme Court explained why the sentencing
statute in question called for a categorical approach. First, the
statute in Taylor referred to persons who had been “convic-
t[ed]” of certain crimes, rather than persons who had “com-
mitted” such crimes, reflecting Congress’s intent that “the
sentencing court . . . look only to the fact that the defendant
had been convicted of crimes falling within certain categories,
and not to the facts underlying the prior convictions.” 

Second, the legislative history of the act suggested that
Congress “generally took a categorical approach to predicate
offenses,” because “no one suggested that a particular crime
might sometimes count towards enhancement and sometimes
not, depending on the facts of the case.” 

Third, the
“practical difficulties and potential unfairness of a factual
approach are daunting.” 

thus instructs that in determining whether a
provision of federal law calls for a categorical approach or an
examination of “the facts underlying prior convictions,” we
turn to the ordinary tools of statutory construction, relying pri-
marily on the language of the statute but making reference to
the legislative history and practical effects to the extent neces-
sary to illuminate the meaning of the plain language. See also

(determining whether a statute
called for a categorical or non-categorical approach by relying
primarily on the language of the statute, but also considering
10638                UNITED STATES v. BYUN
the practical concern that very few state statutes include as an
element the conduct that Congress hoped to address).

   [13] Applying this approach to the “tier II” category, we
conclude that, as to whether an individual is a “tier II”
offender, the language of the statute points strongly toward a
non-categorical approach with regard to the age of the victim.
The statute provides that an individual is a tier II sex offender
when his or her crime is “comparable to or more severe than”
a violation of § 2423(a) “when committed against a minor.”
§ 16911(3)(A) (emphasis added). The use of the word “com-
mitted,” rather than “convicted” persuasively indicates that, in
determining whether the victim of Byun’s crime was a minor,
we may consider not only the elements of the crime of which
Byun was convicted but her actual conduct. See 

(assuming that use of “committed” with regard
to one aspect of a crime allowed application of non-
categorical approach with regard to that aspect); cf. 

(noting that the use of the word “convicted,”
rather than “committed,” required an examination only of the
elements necessary for a conviction, rather than any underly-
ing acts).

   [14] While the language of the statute is somewhat more
ambiguous with regard to whether a categorical approach
must be applied to all elements of a “specified offense against
a minor,” the close connection between “specified offense[s]
against a minor” and tier II offenses, as well as the history of
the statute, support the conclusion that a non-categorical
approach to the age of the victim is permitted with respect to
that category as well. Section 16911(1) defines a sex offender
as “an individual who was convicted of a sex offense”
(emphasis added), rather than an individual who committed,
or engaged in conduct constituting, such an offense. But the
statute then goes on to describe the two applicable definitions
of “sex offense” in quite different ways: The language used
in defining the first category of “sex offenses” suggests
strongly that only a categorical approach is appropriate as to
                     UNITED STATES v. BYUN                 10639
that category, as it includes only criminal offenses having an
“element involving a sexual act or sexual contact with anoth-
er.” § 16911(5)(A)(I) (emphasis added). The specific refer-
ence to an “element” requires an analysis of the statutory
elements, rather than an examination of the underlying facts.
See United States v. Sherbondy, 

, 1005 (9th Cir.
1988) (holding that the use of “the phrase ‘as an element’
requires an examination of the statute that delineates the
offense of which the defendant was convicted and precludes
any inquiry into the defendant’s actual conduct.”).

   In contrast, the “sex offense” category here pertinent, “a
criminal offense that is a specified offense against a minor,”
contains no reference to the crime’s “elements.” Further, the
definition of “specified offense[s] against a minor” begins
with language stating that such offenses must be “against a
minor” and then lists offenses such as “kidnapping,” “false
imprisonment,” and “[u]se in a sexual performance,”
§ 16911(7)(A), (B), (D), that do not refer to the identity of the
victim. That is, the definition suggests that any kidnapping
offense becomes a “specified offense against a minor” when
the victim is a minor. Finally, and critically, the list of speci-
fied offenses against a minor includes “[a]ny conduct that by
its nature is a sex offense against a minor,” § 16911(7)(I)
(emphasis added), suggesting again that for the category of
“specified offense[s] against a minor,” it is the underlying
“conduct,” not the elements of the crime of conviction, that
matter.

   [15] In sum: Congress did not define “specified offense
against a minor” in terms of elements, spoke of “an offense
against a minor” and then listed broad offenses such as kid-
napping, and expressly referred to “conduct” in one part of
the definition. The tier II sex offender provision also clearly
permits a non-categorical approach to determining the age of
the victim of the crime, and given the close connection
between these two sections of the statute, Congress likely
intended that both be interpreted similarly with regard to
10640                   UNITED STATES v. BYUN
ascertaining the age of the victim. Given all these textual
clues, and even though use of the word “convicted” at the out-
set with regard to “sex offender[s]” creates a modicum of
ambiguity, the best reading of the statutory structure and lan-
guage is that Congress contemplated a non-categorical
approach as to the age of the victim in determining whether
a particular conviction is for a “specified offense against a
minor.”12

   [16] The legislative history of the statute fully supports this
conclusion. This history shows that Congress intended to
include all individuals who commit sex crimes against
minors, not only those who were convicted under a statute
having the age of the victim as an element. The Act is entitled
the “Adam Walsh Child Protection and Safety Act,” and the
legislative history reveals substantial discussion of the neces-
sity of identifying all child predators.13 See, e.g., H.R. REP.
  12
      We have previously considered whether a statute might permit one
element or aspect of a crime to be determined by looking to the underlying
facts, while a “conviction” is required as to the other elements of the
crime. In United States v. Belless, we concluded that, under 18 U.S.C.
§ 922(g)(9), which makes possession of a firearm illegal for anyone “who
has been convicted in any court of a misdemeanor crime of domestic vio-
lence,” domestic violence crimes were “those crimes that are in fact com-
mitted against persons who have a domestic relationship specified in the

(emphasis added). See also White v. Dept. of
Justice, 

, 1364-67 (Fed. Cir. 2003) (similarly holding that
a non-categorical approach was permitted with regard to the nature of the
defendant’s relationship with the victim). In Tokatly v. Ashcroft, in con-
trast, we concluded that a categorical approach must be applied with
respect to all aspects of a “crime of domestic violence” in the immigration
context, despite the fact that the immigration statute arguably drew a dis-
tinction between the element of “violence” and the requirement that the
crime be committed within a domestic 

. Our
decisions in Tokatly and Belless are not easily reconciled. See Cisneros-
Perez v. Gonzales, 

, 392 (9th Cir. 2006). We need not deter-
mine, however, whether this case is more similar to Belless or Tokatly,
because there is substantially more support, both in the text of the statute
and the legislative history, that Congress intended that the identity of the
victim may be established without application of a categorical approach.
   13
      Much of what ultimately became the Adam Walsh Act was introduced
in the House in 2005 as part of a larger bill containing provisions on gang
                        UNITED STATES v. BYUN                       10641
NO. 109-218, at 22-23 (2005) (stating, in a section entitled
“Background and Need for the Legislation,” that “[t]he sexual
victimization of children is overwhelming in magnitude,” and
noting that the median age of the victims of imprisoned sex
offenders in one study “was less than 13 years old”); 152
Cong. Rec. H657, H676 (daily ed. Mar. 8, 2006) (statement
of Rep. Sensenbrenner) (purpose of the act is to “better pro-
tect our children from convicted sex offenders”); 

(statement of Rep. Poe) (bill will “mak[e] sure that our chil-
dren are safer” and target “child predators”); 

(statement of Sen. Hatch) (in explaining his support for the
bill, stating “I am determined that Congress will play its part
in protecting the children of . . . America”). The language of
the statute similarly evidences Congress’s intent to require all
those who commit sex crimes against children to register as
sex offenders. The section defining “specified offense[s]
against a minor” is entitled “[e]xpansion of definition of
‘specified offense against a minor’ to include all offenses by
child predators,” § 16911(7). See Bhd. of R.R. Trainmen v.
Baltimore & Ohio R.R. Co., 

, 529 (1947) (noting
that “[f]or interpretative purposes, [the heading of a section is]
of use . . . when [it] shed[s] light on some ambiguous word

violence and protection for federal judges. H.R. 3132, 109th Cong. (2005).
H.R. 3132 contains the same definition of a “specified offense against a
minor,” but does not contain the definitions of different tiers of sex
offenders. The bill was reintroduced in the house in 2006 as H.R. 4472,
109th Cong. (2006), without a new report and was passed under “suspen-
sion of the rules,” according to which “floor debate is limited, all floor
amendments are prohibited, and a two-thirds vote is required for final pas-
sage.” Elizabeth Rybicki, CRS Report for Congress, Suspension of the
Rules in the House: Principal Features, available at http://
www.rules.house.gov/Archives/98-314.pdf. The Senate version of the bill,
S. 1086, 109th Cong. (2006), was reported out of committee in March of
2006 without a written committee report. The cited House Report was thus
prepared only with regard to H.R. 3132.
10642                   UNITED STATES v. BYUN
or phrase,” but it “cannot . . . limit that which the text makes
plain”).14

   [17] Given the language and structure of the statute, as well
as its legislative history, we conclude that, as to the age of the
victim, the underlying facts of a defendant’s offense are perti-
nent in determining whether she has committed a “specified
offense against a minor” and is thus a sex offender.15 Because
Byun’s plea agreement reveals that she in fact imported a
minor for purposes of prostitution, her offense is a “specified
offense against a minor” and she is a sex offender under
SORNA.

   AFFIRMED.




  14
      Were we interpreting a criminal statute, we would be considerably
more hesitant to conclude that an element, such as the age of a victim, can
be determined by a judge after examining the underlying facts of a crime.
As the Supreme Court noted in Shepard v. United States, 

(2005) (plurality opinion), allowing a judge in a criminal proceeding to
look beyond charging documents to the underlying facts of an earlier
offense may well implicate the Sixth Amendment’s requirement that all
facts, other than that of a prior conviction, that increase the maximum pun-
ishment for a crime must be proven to a jury beyond a reasonable doubt.

Here, however, we are faced not with a statute that imposes
criminal punishment, but rather with a civil statute creating registration
requirements. See Smith v. Doe, 

, 105-06 (2003) (holding that
Alaska’s sex offender registration statute is civil and nonpunitive, and
therefore retroactive application of the Act does not violate the Ex Post
Facto clause); Hatton v. Bonner, 

, 961-67 (9th Cir. 2004)
(reaching the same conclusion regarding California’s sex offender regis-
tration statute). Byun does not argue that Sixth Amendment protections
are at issue here. We do not, of course, decide any Sixth Amendment
question, as none is before us.
   15
      As it is not necessary to our holding, we draw no conclusion as to
whether a non-categorical approach is permitted with regard to any facts
other than the age of the victim.