FOR PUBLICATION
 UNITED STATES COURT OF APPEALS
      FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA,                  No. 08-30231
                Plaintiff-Appellee,
               v.                             DC No.
                                          1:06-cr-0016 CCL
TYRONE JACKSON, AKA Ty,
                                              OPINION
             Defendant-Appellant.
                                      
       Appeal from the United States District Court
               for the District of Montana
       Charles C. Lovell, District Judge, Presiding

                   Argued and Submitted
            April 7, 2009—Seattle, Washington

                   Filed August 14, 2009

    Before: Betty B. Fletcher, A. Wallace Tashima, and
            Sidney R. Thomas, Circuit Judges.

                Opinion by Judge Tashima




                           11139
                 UNITED STATES v. JACKSON           11141




                       COUNSEL

Michael Donahoe, Federal Defenders of Montana, Helena,
Montanta, for the defendant-appellant.

William W. Mercer, United States Attorney, Billings, Mon-
tana, for the plaintiff-appellee.


                       OPINION

TASHIMA, Circuit Judge:

 Tyrone Jackson appeals the district court’s denial of his
motion for a sentence reduction pursuant to 18 U.S.C.
11142              UNITED STATES v. JACKSON
§ 3582(c)(2). Jackson, who pled guilty to possession of crack
cocaine with intent to distribute, contends that the district
court should have reduced his sentence on the basis of
Amendment 706 to the U.S. Sentencing Guidelines
(“U.S.S.G.”), which lowered the guideline ranges for crack
cocaine offenses. Although the district court waived the man-
datory minimum sentence in Jackson’s case, we hold that his
sentence was nevertheless based on the statutory mandatory
minimum (the “mandatory minimum”), not on a guideline
range that was affected by Amendment 706. Therefore, we
affirm the district court’s conclusion that it did not have the
authority to grant relief under § 3582(c)(2).

         I.   Jurisdiction and Standard of Review

   We have jurisdiction to consider Jackson’s appeal pursuant
to 28 U.S.C. § 1291. See United States v. Colson, No. 08-
10287, 

(9th Cir. July 23, 2009). Because
Jackson’s appeal is based on a question of law, and he does
not challenge a discretionary decision of the district court not
to reduce his sentence, we apply de novo review. See United
States v. Paulk, No. 08-50229, 

, at *1 (9th
Cir. Aug. 6, 2009) (per curiam) (as amended).

                      II.   Background

   Jackson pled guilty to possession of cocaine base, com-
monly known as crack cocaine, with intent to distribute, in
violation of 21 U.S.C. § 841(a)(1). At his sentencing hearing
in February 2007, the district court calculated Jackson’s
offense level as Level 23, and his criminal history category as
Category IV, yielding a guidelines sentencing range of 70-87
months. Because, however, Jackson had previously been con-
victed of a felony drug offense, a minimum sentence of 120
months’ imprisonment was required under 21 U.S.C.
§ 841(b)(1)(B). In recognition of Jackson’s substantial assis-
tance in the prosecution of other offenders, the government
moved the court to depart from the guidelines and impose a
                   UNITED STATES v. JACKSON                11143
sentence less than the mandatory minimum, pursuant to
U.S.S.G. § 5K1.1 and 18 U.S.C. § 3553(e). The district court
granted the motion to waive the mandatory minimum and
imposed a sentence of 90 months’ imprisonment.

   In November 2007, the U.S. Sentencing Commission
issued Amendment 706, which lowered the Sentencing
Guidelines ranges applicable to crack cocaine offenses. Under
the amended guidelines, Jackson’s offense level would have
been 21, rather than 23. The applicable sentencing range for
his criminal history category would have been 57-71 months.
The mandatory minimum under 21 U.S.C. § 841(b)(1)(B),
however, remained unchanged at 120 months.

   In March 2008, Amendment 706 was made retroactive to
defendants who were serving prison sentences for crack
cocaine offenses, see U.S.S.G. § 1B1.10(c), and Jackson
moved for a retroactive reduction in sentence pursuant to 18
U.S.C. § 3582(c)(2) and U.S.S.G. § 1B1.10. The district court
denied Jackson’s motion for resentencing, ruling that it lacked
the authority to reduce Jackson’s sentence because the sen-
tence was based on the 120-month mandatory minimum and
not on a sentencing range. This appeal followed.

                       III.   Discussion

   [1] Ordinarily, a district court may not modify a sentence
once it has been imposed. 18 U.S.C. § 3582(c). An exception
exists “in the case of a defendant who has been sentenced to
a term of imprisonment based on a sentencing range that has
subsequently been lowered by the Sentencing Commission
pursuant to 28 U.S.C. 994(o)[.]” 18 U.S.C. § 3582(c)(2). In
such cases, the court “may reduce the term of imprisonment,
after considering the factors set forth in section 3553(a) to the
extent that they are applicable, if such a reduction is consis-
tent with applicable policy statements issued by the Sentenc-
ing Commission.” 

U.S.S.G. § 5G1.1(b), when
the mandatory minimum for a crime exceeds the sentencing
11144              UNITED STATES v. JACKSON
guideline range, the mandatory minimum becomes the guide-
line sentence, displacing the guideline range. We have held
that a sentence imposed in this circumstance is not “based on”
a guideline range, but rather on the mandatory minimum; as
a result, a defendant sentenced pursuant to a mandatory mini-
mum is ineligible for relief under § 3582(c)(2) even if the
guideline range otherwise applicable to his offense is reduced.
See Paulk, 

, at *2; United States v. Mul-
lanix, 

, 324 (9th Cir. 1996).

   [2] Today we confront a slight variation. The mandatory
minimum applicable to Jackson exceeded the guideline range,
just as was the case in Mullanix and Paulk. In the case at
bench, however, the district court reduced the sentence below
the mandatory minimum pursuant to § 3553(e) in recognition
of Jackson’s substantial assistance in prosecuting other
offenders. We join our sister circuits in holding that a defen-
dant in this circumstance is ineligible for a sentence reduction
under § 3582(c)(2), despite any subsequent reductions in the
guideline ranges. See United States v. Johnson, 

(6th Cir. 2009); United States v. Doe, 

(3d Cir.
2009); United States v. Byers, 

(8th Cir. 2009);
United States v. Hood, 

(4th Cir. 2009); United
States v. Williams, 

(2d Cir. 2009); United States
v. Williams, 

(11th Cir. 2008) (per curiam).

   Jackson argues that he is eligible for resentencing under
§ 3582(c)(2) because, when the court waived the mandatory
minimum, the guideline range was left as the basis for deter-
mining his sentence. In Jackson’s view, when the court
granted a departure below the mandatory minimum pursuant
to 18 U.S.C. § 3553(e), the mandatory minimum sentence
became inoperative and was no longer of relevance.

  [3] We have, however, rejected this argument in a similar
context. See United States v. Auld, 

(9th Cir.
2003). In Auld, the government moved for a waiver of the
mandatory minimum sentence for a defendant who cooper-
                      UNITED STATES v. JACKSON                    11145
ated with police in obtaining the conviction of other offend-
ers. 

The court departed downward from the
mandatory minimum, but nevertheless imposed a sentence
above the guideline range that would have applied in the
absence of the mandatory minimum. 

appealed the sentence and put forward essentially the same
argument that Jackson does in the current case: because the
court granted a departure below the mandatory minimum, the
sentence should have been imposed in accordance with the
Sentencing Guidelines range. 

We disagreed,
holding that, when a statutory minimum is waived, this

      means only that the mandatory nature of the statu-
      tory minimum is dispensed with, thus permitting the
      imposition of a sentence below that minimum.[1] It
      does not mean that the statutory minimum is not to
      be used as the point from which a downward depar-
      ture begins.

If Congress had meant to render mandatory mini-
mums completely inoperative in the case of reductions pursu-
ant to § 3553(e), it would not have simply granted “limited
authority to impose a sentence below a statutory minimum,”
but rather would have used language like that in 18 U.S.C.
§ 3553(f), which authorizes the district court to impose a sen-
tence “without regard to any statutory minimum sentence.”
See 

  [4] The district court’s procedure in imposing Jackson’s
sentence was consistent with the holding in Auld: the court
used the mandatory minimum, not the Sentencing Guidelines
  1
    Auld was decided prior to United States v. Booker, 

(2005), i.e., when the Sentencing Guidelines were mandatory and the dis-
trict court was not permitted to impose a sentence outside the guideline
range in the absence of a ground for departure. Although the guidelines
are now only advisory, the reasoning in Auld remains sound as to the con-
tinuing relevance of a mandatory minimum sentence in determining a sen-
tence under § 3553(e).
11146              UNITED STATES v. JACKSON
range, as the starting point for determining Jackson’s sen-
tence. At the initial sentencing, when deciding how far to
reduce Jackson’s sentence in light of his cooperation with the
investigation, the court began its calculation from the 120-
month minimum, not from the guidelines sentencing range.
The court characterized the 90-month sentence as a 25 percent
reduction from the 120-month minimum, not as an increase
from the guidelines sentencing range. The parties discussed
the guidelines sentencing range, but the court stated that,
because of the mandatory minimum, “for all practical pur-
poses, the [sentence of] 70 to 87 months [the indicated guide-
lines range] is irrelevant.”

   Jackson argues, in the alternative, that he is eligible for a
reduction in sentence under § 3582(c)(2) because, even if the
court was correct to use the mandatory minimum as the start-
ing point for determining his sentence, the sentence was still
based in part on the Sentencing Guidelines. He points out that,
under U.S.S.G. § 5G1.1(b), a mandatory minimum becomes
the guideline sentence only when it exceeds the maximum of
the guideline range. In order to determine whether the manda-
tory minimum takes the place of the guideline range, a district
court must calculate the range indicated by the Sentencing
Guidelines and compare it to the mandatory minimum.
Because the district court was required to take the guideline
range into account when determining Jackson’s sentence,
Jackson argues that the sentence was based on a guideline
range.

   This argument proves too much. Every sentence involving
a mandatory minimum requires a comparison with the range
indicated by the Sentencing Guidelines. By Jackson’s logic,
then, every mandatory minimum sentence would be “based
on” the Sentencing Guidelines, and every defendant sentenced
to a mandatory minimum would be eligible for a reduction if
the otherwise-applicable Sentencing Guidelines were reduced.
This is incompatible with our holding in Paulk, 

, at *2, and also with U.S.S.G. § 1B1.10, cmt. n.1(A),
                   UNITED STATES v. JACKSON                11147
which expressly states that a defendant sentenced to a manda-
tory minimum is ineligible for a § 3582(c)(2) reduction. We
thus reject the argument.

   [5] Finally, Jackson contends that his sentence was based
on the guideline range because, after the district court decided
to grant a departure under § 3553(e), the court was required
to consider the guideline range as one of the § 3553(a) factors
in deciding whether to impose a sentence above or below that
indicated by the departure. But in determining the extent of a
departure under § 3553(e), “[t]he district court may not . . .
consider factors unrelated to the defendant’s assistance.”

; accord 

;
United States v. Williams, 

, 1131-32 (8th Cir.
2007); United States v. Desselle, 

, 182 (5th Cir.
2006). When the district court grants a waiver of the manda-
tory minimum pursuant to § 3553(e), the departure establishes
the new minimum sentence for the defendant, and the court
may not reduce the sentence further on the basis of the
§ 3553(a) factors. United States v. Richardson, 

,
159 (2d Cir. 2008). This is not to say that the district court
should not consult the § 3553(a) factors before imposing a
final sentence. As the Second Circuit explained in Williams,
“only after the court has determined the full extent of the
downward departure it would award based on [the defen-
dant’s] substantial assistance does the court consider other
factors, including those in § 3553(a), to decide whether to
depart to that full 

. In other words, the
court may increase a sentence on the basis of the § 3553(a)
factors, but may not reduce the sentence further.

   [6] Thus, when the district court decided that it would grant
Jackson a downward departure of 25 percent from the 120-
month minimum, it was bound to impose a sentence of no less
than 90 months, regardless of whether Amendment 706 had
been in effect at the time of Jackson’s sentencing. Because the
district court granted Jackson the full benefit of the departure,
a change in the guideline range could not have allowed a fur-
11148              UNITED STATES v. JACKSON
ther reduction in Jackson’s sentence. Thus, Jackson’s sen-
tence was not “based on” the guideline range, and he was not
eligible for resentencing under § 3582(c)(2).

                      IV.   Conclusion

   For the reasons set forth above, the district court was cor-
rect to hold that Jackson was ineligible for resentencing under
§ 3582(c)(2). The judgment of the district court is
AFFIRMED.