                    FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA,                       No. 05-30055
                Plaintiff-Appellee,
               v.                                 D.C. No.
                                               CR-04-00039-SEH
SUE ELLEN STATEN,
                                                  OPINION
             Defendant-Appellant.
                                          
         Appeal from the United States District Court
                 for the District of Montana
          Sam E. Haddon, District Judge, Presiding

                  Argued and Submitted
           December 6, 2005—Seattle, Washington

                        Filed June 7, 2006

      Before: Ronald M. Gould and Marsha S. Berzon,
 Circuit Judges, and William W Schwarzer,* District Judge.

                    Opinion by Judge Berzon




  *The Honorable William W Schwarzer, Senior United States District
Judge for the Northern District of California, sitting by designation.

                                6211
6214               UNITED STATES v. STATEN


                         COUNSEL

June Lord, Great Falls, Montana, for defendant-appellant Sue
Ellen Staten.

William W. Mercer, United States Attorney, and Joseph E.
Thaggard, Assistant United States Attorney, United States
Attorney’s Office, Great Falls, Montana, for plaintiff-appellee
United States of America.


                         OPINION

BERZON, Circuit Judge:

   United States v. Booker held that although district courts
are no longer required to follow the United States Sentencing
                        UNITED STATES v. STATEN                           6215
Guidelines (“Guidelines”), when making sentencing deci-
sions, “the [Sentencing Reform] Act nonetheless requires
judges to take account of the Guidelines together with other
sentencing goals.” 543 U.S. 220, 259 (2005) (citing 18
U.S.C.A. § 3553(a) (Supp. 2004)); see also United States v.
Cantrell, 433 F.3d 1269, 1278 (9th Cir. 2006)
(“[N]otwithstanding that the Guidelines are now effectively
advisory, . . . district courts, while not bound to apply the
Guidelines, ‘should still consult them for advice as to the
appropriate sentence.’ ” (citation omitted)). Concomitantly, as
we have repeatedly held in the aftermath of Booker, we con-
tinue to have a duty to review district courts’ required applica-
tion of the Guidelines. We do so to assure that the district
courts properly appreciate the advice offered by the now-
advisory Guidelines before factoring that advice into their
determination, under 18 U.S.C. § 3553(a), of the appropriate
sentence. See United States v. Mix, 442 F.3d 1191, 1195 (9th
Cir. 2006) (“[A]s was the case before Booker, the district
court must calculate the Guidelines range accurately. A misin-
terpretation of the Guidelines by a district court effectively
means that [the district court] has not properly consulted the
Guidelines.” (last alteration in original) (internal citations and
quotation marks omitted)).

   Conducting the requisite review of the post-Booker applica-
tion of the Guidelines in this case, we conclude that the dis-
trict court failed properly to take account of the appropriate
factors when applying the Guidelines section 2D1.1(b)(5)(B)
enhancement for creating a substantial risk of harm to human
life or the environment. We therefore vacate the sentence
imposed on Sue Ellen Staten and remand for resentencing.

                                      I.

  The events which ultimately resulted in this appeal devel-
oped as follows:1 On October 24, 2003, Sue Ellen Staten and
   1
     The facts recited in this section reflect, for the most part, those recited
in the presentence investigation report (“PSR”) prepared by the probation
office for the district judge. At sentencing, Staten confirmed that she had
no objections to the facts recited in the PSR.
6216                  UNITED STATES v. STATEN
Jennifer Gatewood rented two adjacent rooms at the Terrace
Motel, numbered 8 and 9. Later that night, Staten helped to
carry a microwave into room 8, where Denis K. Loftis, Gate-
wood’s boyfriend, had assembled equipment necessary to
manufacture methamphetamine. Loftis and Staten were
arrested in room 8 by officers who had been tipped off to the
manufacturing operation. Because of the perceived hazardous
environment, the motel was evacuated. A hazardous materials
disposal team seized, among other things, the following items
from the rooms: “a kitchen bowl containing iodine and red
phosphorus; hypodermic syringes, one of which contained a
clear liquid substance; a Pyrex plate with methamphetamine
residue; canning jars containing a liquid substance; razor
blades; a microwave oven; a Fry Daddy deep fat fryer; and
several 20 ounce soft drink bottles containing liquid sub-
stances.” The PSR concluded that Staten had conspired with
Gatewood and Loftis in several manufacturing operations,
which resulted in the “produc[tion] [of] a conservative
amount of one-half gram of methamphetamine” on each occa-
sion.

   Staten pleaded guilty pursuant to a plea agreement to con-
spiracy to manufacture methamphetamine under 21 U.S.C.
§§ 841(a)(1) and 846. The PSR, prepared on July 23, 2004,
prior to the issuance of Booker, assessed a base offense level
of twelve pursuant to Guidelines section 2D1.1(c)(14) and
increased the offense level to twenty seven pursuant to section
2D1.1(b)(5)(B). The latter provides for an increase of three
offense levels or, if the resulting increase is less than twenty
seven, an increase of the offense level to twenty seven “[i]f
the offense involved (i) the manufacture of . . . methamphet-
amine; and (ii) created a substantial risk of harm to (I) human
life . . . ; or (II) the environment.” U.S. Sentencing Guidelines
Manual § 2D1.1(b)(5)(B) (emphases added).2 The PSR also
  2
  The presentence investigation report relied on the 2003 edition of the
Guidelines. Staten’s sentencing occurred on January 27, 2005, at which
                       UNITED STATES v. STATEN                       6217
recommended a two-level decrease for acceptance of respon-
sibility pursuant to section 3E1.1(a) and a one-level decrease
for timely notifying government of her intention to plead
guilty pursuant to section 3E1.1(b). Because Staten fell into
criminal history category III, the PSR concluded that a Guide-
lines imprisonment range of sixty-three to seventy-eight
months was appropriate. See id. ch. 5, pt. A (Sentencing
Table).

  The sentencing hearing occurred just after Booker was
decided. In light of Booker, the district court treated the
Guidelines as “advisory only.” The district court allowed
argument about the PSR at the sentencing hearing and invited
counsel to raise any other pertinent information.

   In response to that invitation, both parties submitted expert
reports with regard to the substantial risk of harm issue. Stat-
en’s expert based his brief report on “the evidence and video
tape in this case.” While “not disput[ing] [that] there exist[ ]
potential dangers for all clandestine methamphetamine labs,”
Staten’s expert

     [could not] state, within a reasonable degree of sci-
     entific certainty, based upon the evidence found, evi-

point the 2004 edition of the Guidelines was in effect. According to the
Guidelines, a district court “shall use the Guidelines Manual in effect on
the date that the defendant is sentenced.” U.S. Sentencing Guidelines
Manual § 1B1.11(a) (2004); see United States v. Benitez-Perez, 367 F.3d
1200, 1205 (9th Cir. 2004) (“A district court must apply the version of the
Sentencing Guidelines in effect on the date of sentencing, unless that
would pose an ex post facto problem.”). It seems, therefore, that the wrong
version of the Guidelines was applied at Staten’s sentencing. The 2004
amendments to the Guidelines, however, did not substantively change sec-
tion 2D1.1(b)(5), or its Application Note; subdivision (b)(5) simply was
redesignated as subdivision (b)(6). See U.S. Sentencing Guidelines Man-
ual § 2D1.1 hist. note (2004); id. app. C, amend. 667 (2004). As the ver-
sion used thus does not matter, we refer, as do the parties, to the 2003
edition of the Guidelines.
6218                UNITED STATES v. STATEN
    dence analyzed, lack of chemical odor notation and
    the video tape, any “real” hazards or dangers existed
    at the scene that would pose a significant threat or
    danger to any persons other than the cook and those
    present in the room.

   The government’s expert presented a report which detailed
various “hazards associated with methamphetamine manufac-
ture.” According to this report, such hazards include the
potential for flash fire caused by the atmospheric concentra-
tion of alcohol; “[the health hazard and dangers] associated
with iodine tinctures or [the] handling of iodine crystals”; the
generation of hydriodic acid, a respiratory irritant; the genera-
tion of hydriodic acid fumes and phosphine gas, both of
which are potentially lethal; the possibility that the coffee or
paint filters used to collect solid red phosphorus might auto-
ignite; the dangers associated with handling caustic lye
(sodium hydroxide); the need to dispose of chemical waste
generated by the manufacturing process; the potential for oth-
ers to be exposed to improperly disposed of waste; and the
potential for subsequent occupants of the location of the man-
ufacture to be “unwitting[ly] expos[ed] to methamphetamine
residue and other hazardous by-products of the manufacturing
process.”

  At sentencing, Deputy Jergens testified that while he was
searching the motel room he found what appeared to be an
uncovered container of iodine and an uncovered container of
Coleman fuel. He also testified that between three and five
people were evacuated from the motel, including two from an
adjacent room.

  Staten objected to the section 2D1.1(b)(5)(B) enhancement
on the ground that the Booker advisory Guidelines remedy
may not be applied to a pre-Booker crime and so, under
Blakely v. Washington, 542 U.S. 296 (2004), the facts sup-
porting the enhancement must be proved beyond a reasonable
doubt. She also maintained that on any burden of proof, the
                    UNITED STATES v. STATEN                  6219
district court did not properly determine that the enhancement
was supported by the established facts. The district court
rejected both arguments, observing that any Guidelines calcu-
lation was “only an advisory component” of the factors it was
obliged to consider under Booker. The district court then
explained that, in its view, the substantial risk of harm
enhancement was applicable. After recognizing that under
Booker it was to consider all the factors set forth in 18 U.S.C.
§ 3553(a), the district court sentenced Staten to sixty-three
months imprisonment with three years of supervised release
to follow, a sentence within the calculated advisory Guide-
lines range.

   Staten now reasserts the objections she raised at her sen-
tencing: She argues, first, that the Booker advisory Guidelines
regime cannot apply to her, as she committed her crime
before Booker was decided, and that the failure to determine
whether the facts supporting the enhancement were proven
beyond a reasonable doubt therefore violated her due process
rights. Second, she argues that the district court erred in deter-
mining that the evidence presented at the sentencing hearing
and the facts established in the PSR support application of the
section 2D1.1(b)(5)(B) substantial risk of harm enhancement.

                               II.

   “We review ex post facto challenges to sentencing deci-
sions de novo.” United States v. Ortland, 109 F.3d 539, 543
(9th Cir. 1997); see also Hunter v. Ayers, 336 F.3d 1007,
1011 (9th Cir. 2003). While the constitutional prohibition
against ex post facto laws “by its terms, applies only to
changes in the law resulting from legislative or executive
action, . . . the [Supreme] Court has extended similar princi-
ples to the Due Process Clause to cover ‘unforseeable [judi-
cial] construction of a criminal statute.’ ” United States v.
Dupas, 419 F.3d 916, 920 n.3 (9th Cir. 2005) (second alter-
ation in original) (quoting Bouie v. City of Columbia, 378
U.S. 347, 354-55 (1964)), cert. denied, 126 S. Ct. 1484 (Mar.
6220                   UNITED STATES v. STATEN
6, 2006). Staten asserts such a due process argument, which
we review as we would a traditional ex post facto argument.

   Under Booker, we review the ultimate sentence imposed
under the factors set forth in 18 U.S.C. § 3553(a) for “reason-
ableness.” Cantrell, 433 F.3d at 1279. If, however, “there was
material error in the Guidelines calculation that serves as the
starting point for the district court’s sentencing decision, we
will remand for resentencing pursuant to 18 U.S.C. § 3742(f),
without reaching the question of whether the sentence as a
whole is reasonable in light of § 3553(a).” Id. at 1280; see
also Mix, 442 F.3d at 1195 (“If the district court incorrectly
construed the Sentencing Guidelines, we must vacate the sen-
tence and remand for resentencing.”).

   “[W]e . . . review ‘the district court’s interpretation of the
Sentencing Guidelines de novo, the district court’s application
of the Sentencing Guidelines to the facts of [a] case for abuse
of discretion, and the district court’s factual findings for clear
error.” Cantrell, 433 F.3d at 1279 (alteration in original)
(quoting United States v. Kimbrew, 406 F.3d 1149, 1151 (9th
Cir. 2005)).3
  3
    Prior to Booker, there was conflict in our case law regarding the stan-
dard of review for a district court’s application of the Guidelines to a par-
ticular sentence. Some pre-Booker decisions employed an abuse of
discretion standard. See, e.g., United States v. Alexander, 287 F.3d 811,
818 (9th Cir. 2002) (“ ‘We review the district court’s application of the
Sentencing Guidelines to the facts of a particular case for abuse of discre-
tion.’ ” (quoting United States v. Leon-Reyes, 177 F.3d 816, 824 (9th Cir.
1999))); United States v. Robinson, 94 F.3d 1325, 1327 (9th Cir. 1996).
Other pre-Booker decisions reviewed a district court’s application of the
Guidelines de novo. See, e.g., United States v. Crawford, 372 F.3d 1048,
1053 (9th Cir. 2004) (en banc) (“The district court’s interpretation and
application of the Sentencing Guidelines are reviewed de novo.”); United
States v. Gonzalez, 262 F.3d 867, 869 (9th Cir. 2001) (per curiam); Ort-
land, 109 F.3d at 543.
   This conflict has continued post-Booker. In United States v. Smith, we
stated that post-Booker, “we review ‘the district court’s application of the
                       UNITED STATES v. STATEN                         6221
                                    III.

                                     A.

   Staten maintains that the Due Process clause “prohibits
courts from applying the Booker remedy to the disadvantage
of any criminal defendant whose crime was committed before
Booker was decided,” and that she therefore is entitled to the
benefit of the Sixth Amendment rule that “[a]ny fact (other
than a prior conviction) which is necessary to support a sen-
tence exceeding the maximum authorized by the facts estab-
lished by a plea of guilty or a jury verdict must be admitted
by the defendant or proved to a jury beyond a reasonable
doubt.” Booker, 543 U.S. at 244; see also Blakely, 542 U.S.
at 301 (“ ‘Other than the fact of a prior conviction, any fact
that increases the penalty for a crime beyond the prescribed
statutory maximum must be submitted to a jury, and proved
beyond a reasonable doubt.’ ” (quoting Apprendi v. New Jer-
sey, 530 U.S. 466, 490 (2000))).

Sentencing Guidelines to the facts of this case for abuse of discretion’ ”
424 F.3d 992, 1015 (9th Cir. 2005) (quoting Kimbrew, 406 F.3d at 1151),
cert. denied, 126 S. Ct. 1477 (Mar. 6, 2006) and sub nom. Bates v. United
States, 126 S. Ct. 1770 (Apr 17, 2006). Both Smith and Kimbrew, though
decided post-Booker, reviewed sentences imposed under the pre-Booker
mandatory Guidelines regime. See Smith, 424 F.3d at 1017; Kimbrew, 406
F.3d at 1154. Mix, a “true” post-Booker case, follows the abuse of discre-
tion standard set forth in Smith. 442 F.3d at 1195 (“We review the applica-
tion of the Sentencing Guidelines to the facts of the case for abuse of
discretion and factual findings for clear error.” (citing Smith, 424 F.3d at
1015)). In contrast, one post-Booker decision indicates that the applicable
standard of review is de novo. See United States v. Williamson, 439 F.3d
1125, 1137 n. 12 (9th Cir. 2006) (“We review the interpretation and appli-
cation of the Guidelines de novo.”).
   As we would conclude that the district court here erred in its application
of the Guidelines under any standard of review, we save for another day
resolution of the standard of review for application of the Guidelines after
Booker.
6222                UNITED STATES v. STATEN
   [1] Our decision in Dupas forecloses this argument. See
419 F.3d at 919-21 (holding that the application of Booker’s
remedial holding to sentencing determinations on direct
review does not violate retroactivity due process concerns),
cert. denied, 126 S. Ct. 1484 (Mar. 6, 2006); see also Mix,
442 F.3d at 1198-99 (following Dupas). Like Dupas, when
Staten committed her crime she had “sufficient warning of the
potential consequences of [her] actions to satisfy . . . due pro-
cess concerns.” Dupas, 419 F.3d at 921 (holding that fair
warning exists where the defendant had notice at the time of
the offense “that his sentence could be . . . set within the
applicable statutory maximum”).

                               B.

  [2] Staten’s sentence was enhanced in accord with section
2D1.1(b)(5)(B) of the Guidelines. That section provides:

    If the offense (i) involved the manufacture of . . .
    methamphetamine; and (ii) created a substantial risk
    of harm to (I) human life other than a life described
    in subdivision (C); or (II) the environment, increase
    [the offense level] by 3 levels. If the resulting
    offense level is less than level 27, increase to level
    27.

U.S. Sentencing Guidelines Manual § 2D1.1(b)(5)(B). Appli-
cation Note 20(A), which applies to section 2D1.1(b)(5)(B),
provides:

    (A) Factors to consider. In determining, for pur-
    poses of subsection (b)(5)(B) or (C), whether the
    offense created a substantial risk of harm to human
    life or the environment, the court shall include con-
    sideration of the following factors:

      (i) The quantity of any chemicals or hazardous or
    toxic substances found at the laboratory, and the
                   UNITED STATES v. STATEN                    6223
    manner in which the chemicals or substances were
    stored.

       (ii) The manner in which hazardous or toxic sub-
    stances were disposed, and the likelihood of release
    into the environment of hazardous or toxic sub-
    stances.

       (iii) The duration of the offense, and the extent of
    the manufacturing operation.

       (iv) The location of the laboratory (e.g., whether
    the laboratory is located in a residential neighbor-
    hood or a remote area), and the number of human
    lives placed at substantial risk of harm.

Id. § 2D1.1(b)(5)(B) cmt. n.20(A) (emphasis added).

   Staten submits that “there was no finding made in accor-
dance” with Note 20(A). We agree, and hold that because the
district court failed to take Note 20(A) into account, a remand
for resentencing is necessary so that the district court can
make the factual determinations required by that note.

   [3] According to the Guidelines, the commentary that
accompanies a given section “may interpret the guideline or
explain how it is to be applied,” and “[f]ailure to follow such
commentary could constitute an incorrect application of the
guidelines.” Id. § 1B1.7. The Guidelines, including enhance-
ments, are ordinarily applied in light of available commen-
tary, including application notes. See Stinson v. United States,
508 U.S. 36, 38 (1993) (“[C]ommentary in the Guidelines
Manual that interprets or explains a guideline is authoritative
unless it violates the Constitution or a federal statute, or is
inconsistent with, or a plainly erroneous reading of, that
guideline.”); United States v. Allen, 434 F.3d 1166, 1173 (9th
Cir. 2006) (“The application notes to the Guidelines are
exactly that — notes about when a particular Guideline
6224               UNITED STATES v. STATEN
applies and when it does not.”); United States v. Lopez-
Garcia, 316 F.3d 967, 970 (9th Cir. 2003) (“We are bound to
follow the application notes.”); United States v. McKinney, 15
F.3d 849, 852 n.8 (9th Cir. 1994) (noting that “the district
court was . . . obliged to assess [the defendant’s] conduct in
light of the ‘appropriate considerations’ listed in the applica-
tion notes”).

   [4] Note 20(A) uses mandatory language. See U.S. Sen-
tencing Guidelines Manual § 2D1.1(b)(5)(B) cmt. n.20(A)
(noting that “for purposes of subsection (b)(5)(B) . . . , the
court shall include consideration of the following factors”
(emphasis added)); see also United States v. Layne, 324 F.3d
464, 469 (6th Cir. 2003) (noting that 2001 amendments to the
Guidelines “made consideration of the factors set out in the
Application Notes to [the substantial risk of harm enhance-
ment] mandatory”). The district court, however, failed for the
most part properly to consult the mandatory Note 20(A) fac-
tors, focusing instead primarily on factors present in any man-
ufacture of methamphetamine: The court at sentencing
observed that the report submitted by the government’s expert
showed that (1) generally, the manufacture of methamphet-
amine creates a hazard to the health of the person engaged in
such manufacture and (2) studies had established that the
manufacture of methamphetamine can leave detectable traces
in the location of manufacture, creating a potential risk of
exposure to later occupants. The court further observed that
Staten’s own expert had confirmed the “potential danger for
all clandestine methamphetamine labs.” (emphasis added).
Based on these observations, the court stated:

       I don’t see anything in that subdivision which, as
    we have noted, is, in its advisory capacity to this
    court, that suggests that a hazard to the cook is
    excluded by the process or that the hazard of han-
    dling methamphetamine that has been manufactured
    is excluded from the implications of the increase
    contemplated.
                   UNITED STATES v. STATEN                    6225
       And I am taking as reasonable evidence the decla-
    ration from the statement of Mr. Ely that the carrying
    out of this process in a closed environment such as
    a hotel room, would put future occupants at the risk
    of unwitting exposure to the residues which are well-
    known to exist where such an operation has been
    carried out.

       Therefore, under the guideline program, and
    emphasizing that this is an advisory matter only, it
    is my determination that the guideline calculation
    increase to an offense level of 27 is in fact appropri-
    ate in this case.

   [5] The general observations made by the district court do
not constitute adequate consideration of factors due under
Note 20(A). Note 20(A) requires analysis of whether, and the
extent to which, the specified considerations pertain on the
facts of the particular case. The language of each Note 20(A)
factor focuses on the circumstances involved in the prosecu-
tion at hand, not on generic dangers posed by methamphet-
amine manufacture: The note requires that the district court
look to the specific “quantity of any chemicals or hazardous
or toxic substances found”; “the manner in which the chemi-
cals or substances were stored”; “the manner in which hazard-
ous or toxic substances were disposed, and the likelihood of
release into the environment”; “the duration of the offense,
and the extent of the manufacturing operation”; and “the loca-
tion of the laboratory (e.g., whether the laboratory is located
in a residential neighborhood or a remote area) and the num-
ber of human lives placed at substantial risk of harm.” U.S.
Sentencing Guidelines Manual § 2D1.1(b)(5)(B) cmt.
n.20(A). As each enumerated consideration is cast in terms
that demand inquiry into the details of the particular case, the
district court may not rest application of the enhancement on
facts that are necessarily common to most or every manufac-
ture.
6226               UNITED STATES v. STATEN
   This focus on the specific characteristics of the particular
manufacturing operation is fully consistent with the pertinent
guideline. Section 2D1.1(b)(5)(B) applies where there is “the
manufacture of . . . methamphetamine . . . and . . . a substan-
tial risk of harm.” Id. § 2D.1.1(b)(5)(B) (emphasis added).
The conjunction indicates that the “substantial risk of harm”
must be in addition to those inherent in the manufacture of
methamphetamine.

   [6] Here, the district court’s reasons for applying the
enhancement were, for the most part, not specific in nature,
as required by Note 20(A). The court noted that
all clandestine methamphetamine labs create a potential for
danger, a consideration that is not pertinent under Note 20(A).
The court then emphasized that nothing in the language of the
enhancement precluded taking into account the risk posed to
persons engaged in the manufacture of the drug or those han-
dling the final product. The latter consideration, however, is
always true for methamphetamine manufacture — someone
will always be producing the drug and someone will always
be handling the end product. The purpose of Note 20(A) —
which, under section 2D1.1(b)(5)(B), applies exclusively to
the production of methamphetamine and amphetamine — is
to distinguish specific harms from generic ones, so as to jus-
tify a higher sentence than ordinarily attaches to the manufac-
ture of those drugs. The district court’s reliance on generic
harms, such as the usual potential for harm to “the cook,” was
therefore improper.

   The only case-specific factor spelled out in Note 20(A) that
the district court mentioned was “the location of the laborato-
ry,” here, a motel room. Although the consideration that
potential future motel room occupants who might come into
contact with methamphetamine traces is case-specific, section
2D1.1(b)(5)(B) requires that the risk to human life and the
environment must be “substantial” for the enhancement to
apply. Note 20(A) specifies considerations pertinent to the
substantiality requirement, including the quantity of toxic sub-
                       UNITED STATES v. STATEN                        6227
stances found, the manner in which they were stored, and the
duration and extent of the manufacturing operation. The dis-
trict court did not mention these considerations, even though
the evidence showed an operation of short duration and
extent. Yet, these factors are pertinent to whether the location-
specific danger identified — the danger that future occupants
might inhale or ingest methamphetamine residue — is sub-
stantial.

   [7] We conclude that the district court’s application of the
section 2D1.1(b)(5)(B) enhancement, based in part on generic
factors and in part on inadequate consideration of the Note
20(A) factors, constitutes reversible legal error.4 See McKin-
ney, 15 F.3d at 853 n.8 (finding district court’s failure to con-
sider application note factors to constitute reversible error).

                                    C.

   [8] There is an additional reason that the district court’s
factual findings were inadequate: The government recognizes
that the fifteen-level enhancement applied below resulted in
a disproportionate sentence under the now advisory guidelines
“since it increased [Staten’s] offense level by more than four
levels and more than doubled her sentence.” The government
accordingly posits that the facts underlying the sentence
enhancement had to be proved by clear and convincing evi-
dence, instead of a preponderance of the evidence, relying on
pre-Booker case law to that effect. See United States v. Pey-
ton, 353 F.3d 1080, 1088 (9th Cir. 2003) (“The application of
the preponderance of the evidence standard, as opposed to the
clear and convincing standard, violate[s] due process rights
  4
    We do not mean to say that the district court must find each factor
mentioned in Note 20(A) satisfied to apply the section 2D1.1(b)(5)(B)
enhancement. All the district court is obliged to do is consider the factors
and, applying those that are relevant, determine whether the particular
manufacturing operation created a substantial risk of harm to human life
or the environment in light of those relevant factors.
6228                  UNITED STATES v. STATEN
only if it le[ads] to enhancements that ha[ve] an ‘extremely
disproportionate effect on the sentence relative to the offense
of conviction.’ ” (quoting United States v. Mezas de Jesus,
217 F.3d 638, 642 (9th Cir. 2000))); United States v. Jordan,
256 F.3d 922, 927-29 (9th Cir. 2001) (noting that enhance-
ments that have a disproportionate impact on sentences must
be established by clear and convincing evidence). We agree
with the government that the clear and convincing standard
still obtains for an enhancement with an extremely dispropor-
tionate effect, even though the enhancement now results in the
calculation of an advisory rather than a mandatory Guidelines
sentence.

   In the aftermath of Booker, we have noted that while the
preponderance of the evidence standard will still generally
satisfy due process concerns, a heightened burden may some-
times be imposed. See United States v. Dare, 425 F.3d 634,
642 (9th Cir. 2005) (noting, in a post-Booker review, that
“[a]s a general rule, the preponderance of the evidence stan-
dard is the appropriate standard for factual findings used for
sentencing,” but, where an extremely disproportionate sen-
tence results from the application of an enhancement, “ ‘the
government may have to satisfy a “clear and convincing”
standard’ ” (quoting United States v. Hopper, 177 F.3d 824,
833 (9th Cir. 1999))).5 Also, in United States v. Lynch, a post-
Booker case that does not mention Booker, we reiterated the
pre-Booker rule that “when a sentencing factor has an
extremely disproportionate effect on the sentence relative to
the conviction, the government must prove such a factor by
clear and convincing evidence.” 437 F.3d 902, 916 (9th Cir.
2006) (en banc) (per curiam).

  The continuing obligation of the district courts to calculate
accurately the appropriate Guidelines sentence triggers the
  5
   In Dare, however, we declined to extend this heightened disproportion-
ate impact standard to “statutory mandatory minimum sentence[s].” 425
F.3d at 642.
                       UNITED STATES v. STATEN                      6229
very same due process concerns which led to the “dispropor-
tionate impact” rule in the first place.6 In United States v.
Restrepo, we held that generally “due process does not require
a higher standard of proof than preponderance of the evidence
to protect a convicted defendant’s liberty interest in the accu-
rate application of the Guidelines,” 946 F.2d 654, 661 (9th
Cir. 1991) (en banc), but recognized that an exception to this
general rule might be required “when a sentencing factor has
an extremely disproportionate effect on the sentence relative
to the offense of conviction,” id. at 659; Jordan, 256 F.3d at
930 (“It is now settled that when a sentencing factor has an
extremely disproportionate impact on the sentence relative to
the offense of conviction, due process requires that the gov-
ernment prove the facts underlying the enhancement by clear
and convincing evidence.”). We reached this conclusion rely-
ing, in large part, on United States v. Kikumura, 918 F.2d
1084 (3d Cir. 1990). See United States v. Valensia, 222 F.3d
1173, 1179 (2000); Restrepo, 946 F.2d at 646 n.1, 661 n.12.

   The Third Circuit in Kikumura explained that while “less
procedural protection is so clearly appropriate in the majority
of sentencing cases,” where the enhancement represents the
overwhelming proportion of the punishment imposed, “a
court cannot reflexively apply the truncated procedures that
are perfectly adequate for all of the more mundane, familiar
sentencing determinations.” Kikumura, 918 F.2d at 1100-01;
see id. at 1099 (“Though long recognized as a practical neces-
sity, real offense sentencing can create the potential for signif-
icant unfairness. This is so because every factual
consideration deemed relevant for sentencing purposes must
be established through a collateral, post-verdict adjudication
at which the applicable procedural protections are signifi-
cantly lower than those applicable at the trial itself.”). To
  6
   The Sixth Amendment concerns underlying Apprendi and its progeny
are not the same as the due process concerns implicated here. See Booker,
543 U.S. at 233 (noting that if advisory rather than mandatory, the use of
the Guidelines does not implicate the Sixth Amendment).
6230                   UNITED STATES v. STATEN
accommodate these concerns, the Third Circuit crafted a reso-
lution, adopted by this circuit, under which a district court is
required to “ratchet up certain, though not necessarily all, of
the procedural protections afforded a defendant at sentencing,
so as more closely to resemble those afforded at trial,” by
applying the clear and convincing evidence standard to sen-
tencing factors that disproportionately impact the overall sen-
tence. Id. at 1101; see Valensia, 222 F.3d at 1179 (discussing
Kikumura).

   [9] Although the Guidelines do not control the district
court’s ultimate sentence any longer, they must, as a first step,
be consulted and accurately assessed. See United States v.
Jennings, 439 F.3d 604, 606 (9th Cir. 2006) (noting that “dis-
trict courts must, after Booker, consult the Guidelines for
advice in fashioning appropriate sentences and must do so
accurately” (emphasis added)).7 As the concern with accuracy
remains critical, so does the concern that enhancements hav-
ing a drastic impact be determined with particular accuracy.

   [10] We hold, accordingly, that Booker has no impact on
the due process concerns which require that enhancements
resulting in disproportionate, albeit advisory, Guidelines sen-
tences find support in facts established by clear and convinc-
ing evidence. On remand, therefore, if the application of
section 2D1.1(b)(5)(B) again results in a disproportionate sen-
tence, the enhancement must be supported by facts estab-
lished by clear and convincing evidence.
  7
    Booker makes clear that its remedial fix is intended to “make the
Guidelines system advisory while maintaining a strong connection
between the sentence imposed and the offender’s real conduct — a con-
nection important to the increased uniformity of sentencing that Congress
intended its Guidelines system to achieve.” 543 U.S. at 246 (emphasis
added). We note that Booker furthers the very same interests that animated
the Third Circuit in Kikumura. See 918 F.2d at 1098-1102 (discussing the
problems associated with “a system that metes out punishment on the
basis of a defendant’s actual conduct in a particular case”).
                   UNITED STATES v. STATEN                 6231
                              IV.

   [11] We vacate the imposed sentence and remand to the
district court for resentencing in order that it have the oppor-
tunity to consider whether the section 2D1.1(b)(5)(B)
enhancement is applicable in light of Note 20(A).

  VACATED and REMANDED.
