FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA,                  No. 08-30339
                 Plaintiff-Appellee,          D.C. No.
                v.                        CV-07-2119-WFN
PHILLIP WILLIAM GEORGE,                     ORDER AND
              Defendant-Appellant.
                                             OPINION

      Appeal from the United States District Court
         for the Eastern District of Washington
     Wm. Fremming Nielson, District Judge, Presiding

                   Argued and Submitted
             June 2, 2009—Seattle, Washington

                 Filed September 29, 2010

  Before: William C. Canby, Jr., David R. Thompson, and
          Consuelo M. Callahan, Circuit Judges.

                Opinion by Judge Thompson




                            16583
16586              UNITED STATES v. GEORGE


                         COUNSEL

Rebecca Louise Pennell, Assistant Federal Public Defender,
Yakima, Washington, for the defendant-appellant.

Alexander C. Ekstrom, Assistant United States Attorney,
Yakima, Washington, for the plaintiff-appellee.


                          ORDER

  The Petition for Panel Rehearing is granted in part. The
Opinion in this case filed August 25, 2009, 

(9th
Cir. 2009), is withdrawn, and is replaced by the Opinion filed
with this order.

  Subsequent petitions for panel rehearing and for rehearing
en banc may be filed.


                         OPINION

THOMPSON, Senior Circuit Judge:

   Defendant-Appellant Phillip William George (“George”)
was convicted of the federal crime of sexual abuse of a minor
on an Indian reservation in violation of 18 U.S.C. §§ 2243(a)
and 1153. He served his sentence for that offense, but then he
failed to register as a sex offender in violation of the Sex
Offender Registration and Notification Act (“SORNA”), 18
                          UNITED STATES v. GEORGE                       16587
U.S.C. § 2250. He was convicted of that offense in 2008, pur-
suant to a conditional guilty plea, and now appeals that con-
viction. He contends his conviction is invalid because the
state where he was required to register, Washington, had not
implemented SORNA. He also argues SORNA’s registration
requirement is an invalid exercise of congressional power and
violates the Ex Post Facto Clause of the Constitution.

   We have jurisdiction under 28 U.S.C. § 1291, and we
affirm George’s conviction.

                                       I

            Washington’s Failure to Implement SORNA

   [1] On July 27, 2006, the Adam Walsh Child Protection
and Safety Act of 2006 became law. Public Law 109-248,
Secs. 1-155, 120 Stat. 587, 590-611 (2006). Section 141 of
the Act includes SORNA.1 On February 28, 2007, the Attor-
  1
   SORNA’s registration requirements are set forth in 42 U.S.C. § 16913,
and provide:
      a.   In general
      A sex offender shall 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 student. For initial
      registration purposes only, a sex offender shall also register in the
      jurisdiction in which convicted if such jurisdiction is different
      from the jurisdiction of residence.
      b.   Initial registration
      The sex offender shall initially register —
      (1) before completing a sentence of imprisonment with respect
      to the offense giving rise to the registration requirement; or
      (2) not later than 3 business days after being sentenced for that
      offense, if the sex offender is not sentenced to a term of impris-
      onment.
      c.   Keeping the registration current
16588                 UNITED STATES v. GEORGE
ney General issued an interim rule, clarifying that SORNA
applies to all sex offenders regardless of when they were con-
victed. 72 Fed. Reg. 8894, 8896 (Feb. 28, 2007). “SORNA’s
direct federal law registration requirements for sex offenders
are not subject to any deferral of effectiveness. They took
effect when SORNA was enacted on July 27, 2006, and cur-
rently apply to all offenders in the categories for which
SORNA requires registration.” 

  If a sex offender fails to register as required under § 16913,
he or she can be prosecuted under 18 U.S.C. § 2250. Section
2250 states:

    (a) In general. —Whoever—

    (1) is required to register under [SORNA];

   A sex offender shall, not later than 3 business days after each
   change of name, residence, employment, or student status, appear
   in person in at least 1 jurisdiction involved pursuant to subsection
   (a) of this section and inform that jurisdiction of all changes in
   the information required for that offender in the sex offender reg-
   istry. That jurisdiction shall immediately provide that information
   to all other jurisdictions in which the offender is required to reg-
   ister.
   d.   Initial registration of sex offenders unable to comply with
        subsection (b) of this section
   The Attorney General shall have the authority to specify the
   applicability of the requirements of this subchapter to sex offend-
   ers convicted before July 27, 2006 or its implementation in a par-
   ticular jurisdiction, and to prescribe rules for the registration of
   any such sex offenders and for other categories of sex offenders
   who are unable to comply with subsection (b) of this section.
   e.   State penalty for failure to comply
   Each jurisdiction, other than a Federally recognized Indian tribe,
   shall provide a criminal penalty that includes a maximum term of
   imprisonment that is greater than 1 year for the failure of a sex
   offender to comply with the requirements of this subchapter.
                   UNITED STATES v. GEORGE               16589
    (2)(A) is a sex offender as defined for the purposes
    of [SORNA] by reason of a conviction under Federal
    law (including the Uniform Code of Military Jus-
    tice), the law of the District of Columbia, Indian
    tribal law, or the law of any territory or possession
    of the United States; or

    (B) travels in interstate or foreign commerce, or
    enters or leaves, or resides in, Indian country; and

    (3) knowingly fails to register or update a registra-
    tion as required by [SORNA];

    shall be fined under this title or imprisoned not more
    than 10 years, or both.

  George argues that he may not be indicted for a failure to
register under SORNA because SORNA’s registration
requirements become effective only after they have been
implemented by an applicable state.

   [1] Whether an applicable state’s failure to implement
SORNA precludes a federal prosecution for failure to register
as a sex offender in that state is a matter of first impression
within our circuit. George is correct that SORNA includes a
provision requiring implementation by each state. 42 U.S.C.
§ 16924(a). George, however, misconstrues the scope and
effect of SORNA’s implementation provision. That the states
have until July 2009 to implement the administrative portions
of SORNA, does not preclude federal prosecution for
George’s failure to register under SORNA. 72 Fed. Reg. at
8895 (“In contrast to SORNA’s provision of a three-year
grace period for jurisdictions to implement its requirements,
SORNA’s direct federal law registration requirements for sex
offenders are not subject to any deferral of effectiveness.”).

   SORNA requires states to implement sex offender regis-
tries which comply with SORNA requirements by July 2009
16590               UNITED STATES v. GEORGE
or lose part of their federal funding. 42 U.S.C. §§ 16924(a);
16925(a); 72 Fed. Reg. 30210, 30211. With regard to the
requirements that individuals register, SORNA establishes a
criminal offense for the failure to register or to update a regis-
tration. 18 U.S.C. § 2250; 72 Fed. Reg. 8894, 8895.

   [3] There is no clear direction from Congress instructing
that an individual’s obligation to register is dependent on a
state’s implementation of SORNA. See Gozlon-Peretz v.
United States, 

, 404 (1991). Indeed, it is not so
dependent, as explained by the Eighth Circuit in United States
v. May, 

, 916-19 (8th Cir. 2008), cert. denied,

(2009), adopted by the Tenth Circuit in United
States v. Hinkley, 

, 930 (10th Cir. 2008). Other
circuits have reached the same result. See United States v.
Guzman, 

, 93 (2nd Cir. 2010) (“SORNA creates
a federal duty to register with the relevant existing state regis-
tries regardless of state implementation of the specific addi-
tional requirements of SORNA.”); United States v. Brown,

, 1347-49 (11th Cir. 2009); United States v.
Gould, 

, 463-66 (4th Cir. 2009). Without regard
to whether SORNA is implemented by Washington or any
other state, registration under it is required. We hold that
George violated SORNA by failing to register as a sex
offender.

   George argues that an interpretation determining 18 U.S.C.
§ 2250 to be applicable pre-implementation by an applicable
state renders the statute impermissibly vague. In support of
this argument, he contends that such an interpretation leaves
it unclear what it means to register as a sex offender “as
required by SORNA” when a state’s registration system is not
“SORNA-compliant.”

   [4] This argument is without merit because George was
required to register as a sex offender even before the enact-
ment of SORNA. As stated in the plea agreement he entered
in this case, he had signed a notice of conditions of registra-
                       UNITED STATES v. GEORGE                      16591
tion in connection with his 2003 sexual abuse conviction in
the United States District Court for the District of Idaho
“which included a requirement to provide notice of any
change of address, and if [he] should move to another state,
to register in the state and notify Idaho of the move.” More-
over, § 2250 plainly requires a sex offender to register and
update any registration according to SORNA’s requirements.
18 U.S.C. § 2250(a). Under 42 U.S.C. § 16913, which sets out
“Registry requirements for sex offenders,” a sex offender
must register, registration must be kept current, and for initial
registrations, a sex offender must register in the jurisdiction
of conviction if different from the jurisdiction of residence.
These requirements are clear and easy to understand. The
government is correct in that “[i]t is a reasonable construction
of 18 U.S.C. § 2250 that the registration requirements men-
tioned should be found in 42 U.S.C. § 16913, the section from
SORNA entitled ‘Registry requirements for sex offenders.’ ”

                                    II

                          Commerce Clause

   George contends that SORNA’s registration requirements
are outside of Congress’s commerce clause powers. We dis-
agree.

   [5] Congress may regulate interstate commerce in three sit-
uations: (1) “the use of the channels of interstate commerce”;
(2) “the instrumentalities of interstate commerce, or persons
or things in interstate commerce, even though the threat may
come only from intrastate activities”; and (3) “those activities
having substantial relation to interstate commerce.” United
States v. Lopez, 

, 558-59 (1995).2 Congress has
  2
    George cites United States v. Waybright, 

(D.Mont.2008) which found that § 16913 was not constitutional because
it (1) does not fit within the Lopez prongs, (2) is not economic in nature,
and (3) created a separate statutory scheme of national regulation of sex
16592                  UNITED STATES v. GEORGE
the ability to make all laws that are “necessary and proper”
for the accomplishment of its commerce clause power. U.S.
Const. art. I, § 8, cl. 18. Congress’s commerce clause power
can reach intrastate activity that has a substantial effect on
interstate commerce. See Wickard v. Filburn, 

,
125 (1942).

   [6] SORNA was enacted to keep track of sex offenders.
See Carr v. United States, ___ U.S. ___, 

, 2240
(2010) (“[SORNA was] enacted to address the deficiencies in
prior law that had enabled sex offenders to slip through the
cracks.”). Such offenders are required to “register, and keep
registration current, in each jurisdiction” where the offender
lives, works, or goes to school. 42 U.S.C. § 16913(a). As
stated by the Eighth Circuit, “[t]his language indicates Con-
gress wanted registration to track the movement of sex
offenders through different jurisdictions.” United States v.
Howell, 

, 716 (8th Cir. 2009). “Under § 2250,
Congress limited the enforcement of the registration require-
ment to only those sex offenders who were either convicted
of a federal sex offense or who move in interstate commerce.”

U.S.C. § 2250(a)(2)). The requirements of
§ 16913 are reasonably aimed at “regulating persons or things
in interstate commerce and the use of the channels of inter-
state commerce.” 

(quoting 

)
(quotation marks omitted).

   [7] Congress had the power under its broad commerce
clause authority to enact the SORNA. Accord United States
v. Whaley, 

, 258 (5th Cir. 2009); United States
v. Gould, 

, 470-72 (4th Cir. 2009); United States

offenders instead of facilitating implementation of a federal crime under
§ 2250. 

To the extent our reasoning in this opinion differs
from the district court’s decision in Waybright, we disapprove of that deci-
sion. See NASD Dispute Resolution, Inc. v. Judicial Council of State of
Ca., 

, 1069 (9th Cir. 2007).
                      UNITED STATES v. GEORGE                      16593
v. Ambert, 

, 1210 (11th Cir. 2009); United
States v. Hinckley, 

, 940 (10th Cir. 2008), cert.
denied, 

(2009); 

.

   [8] George alternatively argues that Congress does not
have the power to require registration based on his status as
a federal sex offender under 18 U.S.C. § 2250(a)(2)(A).
Again, we disagree. SORNA’s registration requirements in
that section are valid based on the federal government’s “di-
rect supervisory interest” over federal sex offenders. 

. As the Court recently explained in Carr:

     it is entirely reasonable for Congress to have
     assigned to the federal government a special role in
     ensuring compliance with SORNA’s registration
     requirements by federal sex offenders — persons
     who typically would have spent time under federal
     criminal supervision.

Compare United States v. Comstock, 

(2010) (upholding under the Necessary and Proper
Clause a statute that provided for the civil commitment of
sexually dangerous federal prisoners beyond the date they
would otherwise be released). We therefore affirm George’s
conviction based on his status as a federally convicted sex
offender under § 2250(a)(2)(A).3
   3
     Because George’s failure to register occurred after the Attorney Gen-
eral issued the interim order, 72 Fed. Reg. 8894, we need not resolve
whether SORNA’s registration requirements apply to pre-SORNA sex
offenders, like George, upon the statute’s July 27, 2007 enactment or upon
the later February 28, 2007 issuance of the interim order. See 

n.2 (noting, without expressing an opinion, that there is a
“conflict among the Courts of Appeals as to when SORNA’s registration
requirements became applicable to persons convicted of sex offences prior
to the statute’s enactment.”). Either way, SORNA applied to George at the
time of his arrest in Washington in September 2007. And, as we concluded
above, Washington’s failure to implement SORNA does not bar federal
prosecution for George’s failure to register.
16594              UNITED STATES v. GEORGE
                               III

                    Ex Post Facto Clause

   [9] George argues that he may not be indicted for a viola-
tion of SORNA because the registration requirement of
SORNA as applied to him in this case violates the Ex Post
Facto Clause. Article I, Section 9 of the Constitution prohibits
an ex post facto law where the law (1) imposes a greater pun-
ishment on a defendant than when he was convicted of the
underlying offense; (2) makes a punishment for a crime
greater than it was when it was committed; or (3) deprives a
defendant of a defense available at the time the act was com-
mitted. Collins v. Youngblood, 

, 45-46 (1990). For
a criminal penal law to be ex post facto, it must be retrospec-
tive and disadvantage the offender affected by it. Weaver v.
Graham, 

, 29 (1981). “A law is retrospective if it
changes the legal consequences of acts completed before its
effective date.” Miller v. Florida, 

, 430 (1987)
(internal quotation omitted).

   [10] George’s argument fails because he was under a con-
tinuing obligation to register. His violation of SORNA was
his failure to register as a sex offender after he moved to
Washington. The indictment charged George with failing to
register on or about September 27, 2007. That failure
occurred after the statute had been enacted.

   To avoid this result, George argues that the failure to regis-
ter is a one-time crime, rather than a continuing offense. He
moved to Washington before SORNA was enacted, and he
contends his offense, to the extent it was any offense at all,
occurred when he moved there and the offense was complete
when he failed to register within the required time. He cites
Toussie v. United States, 

, 115-122 (1970) for
the proposition that the crime of failing to register as a sex
offender is a one-time offense. The alleged behavior in Tous-
sie, however, was the failure to register for the draft, not the
                   UNITED STATES v. GEORGE                16595
failure to register as a sex offender and, more importantly,
included recognition by the Court that the question of whether
a crime is deemed continuing should include consideration of
the “nature of the crime involved.” 

.

   Other circuits that have considered this issue have held that
the crime of failing to register as a sex offender is a continu-
ing offense. United States v. Dixon, 

, 582 (7th
Cir. 2008) (“[SORNA] creates a continuing offense in the
sense of an offense that can be committed over a length of
time. If the convicted sex offender does not register by the
end of the third day after he changes his residence, he has vio-
lated [SORNA], and the violation continues until he does reg-
ister, just as a prisoner given a two-week furlough is guilty of
escape if he does not appear by the end of the two weeks, and
thus can be prosecuted immediately but his violation contin-
ues as long as he remains at large.”); United States v. Hinck-
ley, 

, 936 (10th Cir. 2008) (“An interpretation
of the sex offender registration requirement that defines it in
any way other than as a continuing offense would result in
absurdity. As the Western District of Virginia points out, ‘It
would be illogical for members of Congress to express con-
cern that thousands of sex offenders who were required to
register under state law were evading those registration
requirements and then exempt those same offenders from
SORNA.’ ” (citation omitted)).

   [11] We interpret the violation of the sex offender registra-
tion requirement as a continuing offense. George violated
SORNA after it was enacted, and after any question of its
application to him had been removed by the Attorney Gener-
al’s ruling, 72 Fed. Reg. 8894, 8896, thus charging him with
a violation was not a violation of the ex post facto clause.

                              IV

                          Conclusion

  The district court correctly denied George’s motion to dis-
miss the indictment. The registration requirement under
16596             UNITED STATES v. GEORGE
SORNA required him to register as a sex offender in the State
of Washington, even though Washington had not imple-
mented the statute. SORNA’s registration requirements are a
valid exercise of congressional power, and do not violate the
ex post facto clause of the Constitution.

  AFFIRMED.