                Rehearing granted, July 21, 2010




                       PUBLISHED


UNITED STATES COURT OF APPEALS
             FOR THE FOURTH CIRCUIT


UNITED STATES OF AMERICA,              
               Plaintiff-Appellant,
               v.                                 No. 09-4119
ANTOINE JEROME PETTIFORD,
              Defendant-Appellee.
                                       
       Appeal from the United States District Court
        for the District of Maryland, at Baltimore.
        Benson Everett Legg, Chief District Judge.
       (1:02-cr-00522-BEL-1; 1:05-cv-02321-BEL)

                 Argued: March 24, 2010

                   Decided: June 3, 2010

  Before TRAXLER, Chief Judge, and WILKINSON and
             DUNCAN, Circuit Judges.



Reversed and remanded with instructions by published opin-
ion. Judge Duncan wrote the opinion, in which Chief Judge
Traxler and Judge Wilkinson joined.


                         COUNSEL

ARGUED: Sujit Raman, OFFICE OF THE UNITED
STATES ATTORNEY, Baltimore, Maryland, for Appellant.
Paresh S. Patel, OFFICE OF THE FEDERAL PUBLIC
2                 UNITED STATES v. PETTIFORD
DEFENDER, Greenbelt, Maryland, for Appellee. ON
BRIEF: Rod J. Rosenstein, United States Attorney, Michael
J. Leotta, Assistant United States Attorney, OFFICE OF THE
UNITED STATES ATTORNEY, Baltimore, Maryland, for
Appellant. James Wyda, Federal Public Defender, Baltimore,
Maryland, for Appellee.


                          OPINION

DUNCAN, Circuit Judge:

   Appellee Antoine Jerome Pettiford pleaded guilty to one
count of being a felon in possession of a firearm in violation
of 18 U.S.C. § 922(g), and received an enhanced sentence of
188 months’ imprisonment, in part because he had five prior
convictions which qualified him as a career criminal under the
provisions of the Armed Career Criminal Act (the "ACCA"),
18 U.S.C. § 924(e). Two of the five state court convictions
were subsequently vacated, and Pettiford brought a petition
under 28 U.S.C. § 2255 for post-conviction relief from the
enhanced federal sentence. The district court granted Petti-
ford’s petition, holding that as a result of the vacatur of the
two state convictions, Pettiford was entitled to relief. The dis-
trict court then resentenced Pettiford to a term of 100 months’
imprisonment. For the reasons that follow, we reverse the dis-
trict court’s order and remand with instructions to reinstate
Pettiford’s original sentence.

                               I.

   On November 21, 2002, a grand jury charged Pettiford with
one count of being a felon in possession of a firearm in viola-
tion of 18 U.S.C. § 922(g). The grand jury determined that on
July 4, 2002, Pettiford, "having been convicted of a crime
punishable by imprisonment for a term exceeding one year,
did knowingly and unlawfully possess . . . a Smith & Wesson
.40 caliber semi-automatic pistol." J.A. 11.
                  UNITED STATES v. PETTIFORD                   3
   On April 1, 2003, the United States Probation Office issued
a criminal history report (the "Special Report"), in which it
considered whether Pettiford was subject to an enhanced
criminal sentence under the ACCA. The ACCA provides that
if a person who violates § 922(g) has "three previous convic-
tions . . . for a violent felony or a serious drug offense, or
both, committed on occasions different from one another,
such person shall be fined under this title and imprisoned not
less than fifteen years." 18 U.S.C. § 924(e)(1). Because Petti-
ford had eight prior violent and serious drug felonies, the
United States Probation Office concluded that he qualified for
an enhanced sentence under the ACCA.

   In a May 28, 2003, letter, Pettiford contested the validity of
three of the eight convictions as ACCA predicates, and the
Special Report was revised to eliminate them on July 9, 2003.
Thereafter, on October 6, 2003, the government filed a
Notice/Information of Enhanced Penalties, in which it
explained that Pettiford was subject to the enhanced penalty
provisions of § 924(e)(1), based in part on the following five
state convictions: (1) a 1993 conviction for possession with
intent to manufacture narcotics; (2) a 1994 conviction for
breaking and entering a dwelling, battery, malicious destruc-
tion, and assault; (3) a 2001 conviction for second-degree
assault; (4) a 2002 conviction for possession with intent to
distribute cocaine; and (5) a 2002 conviction for conspiracy
to distribute and possession with intent to distribute cocaine.

  Pursuant to a written plea agreement, signed on January 16,
2004, Pettiford pleaded guilty to the charged offense. In that
agreement, Pettiford stipulated that he was "an Armed Career
Criminal subject to an enhanced sentence under the provisions
of 18 U.S.C. § 924(e)." J.A. 18. He further stipulated that

    based on the Notice/Information of Enhanced Penal-
    ties filed by the United States on October 6, 2003,
    and as found by the U.S. Probation Office in its pre-
    trial criminal history report, Mr. Pettiford has three
4                     UNITED STATES v. PETTIFORD
     or more prior convictions which qualify him as a
     Armed Career Criminal subject to an enhanced sen-
     tence under the provisions of 18 U.S.C. § 924(e).

J.A. 19. The district court confirmed that Pettiford agreed that
he was subject to an ACCA enhanced sentence in its plea col-
loquy, and again at sentencing.1 Thereafter, the district court
sentenced Pettiford to 188 months’ imprisonment, and Petti-
ford did not appeal this sentence.

   Before sentencing, Pettiford filed in state court a coram
nobis petition for post-conviction relief, seeking to vacate his
two 2002 convictions. On September 7, 2004, after Pettiford
had been sentenced in federal court, the Circuit Court for Bal-
timore County vacated the two 2002 convictions, concluding
that the sentences had been illegal because the court imposed
an invalid period of incarceration as a condition of probation.
Almost a year later, on August 15, 2005, Pettiford filed a peti-
tion under 28 U.S.C. § 2255 for post-conviction relief from
the enhanced federal sentence in the District Court of Mary-
land.

  In his pro se § 2255 petition, Pettiford contended that he
was entitled to relief because as a result of the vacatur of the
two 2002 drug convictions, he no longer qualified as an
armed career criminal. Specifically, he argued that his 1993
   1
     At sentencing, Pettiford’s counsel suggested that Pettiford’s 1993 con-
viction for possession with intent to manufacture narcotics might not count
as an ACCA predicate offense because he thought that under Maryland
law the maximum sentence for conspiracy to distribute cocaine was five
years, which would not meet the threshold for a "serious offense" under
18 U.S.C. § 924(e)(2)(A)(ii). Counsel, however, later retracted that sug-
gestion, noting that he "had someone check and ask around, and it appears
that in fact the maximum penalty may actually [have] been 20 years, . . .
not five." J.A. 82. The district court did not consider this issue because
Pettiford’s counsel, upon further inquiry, explained that resolution of this
issue was irrelevant to his client’s ultimate designation as an armed career
criminal in light of Pettiford’s four other qualifying convictions.
                     UNITED STATES v. PETTIFORD                         5
drug conviction could not have been an ACCA predicate con-
viction because, he alleged, "the judgment and transcript do
not show whether [he] was convicted of conspiracy to possess
with intent to distribute a controlled substance or conspiracy
to merely possess a controlled substance (which [was] Mr.
Pettiford’s recollection)." J.A. 193. Because his 1993 drug
conspiracy conviction was merely a possession offense, Petti-
ford maintained that he had only two remaining convictions
that qualified for ACCA purposes, not three.

   On January 11, 2007, the district court issued an order
appointing a Public Defender to represent Pettiford, and
requiring the Public Defender to verify whether, in addition
to the 1993 conviction, Pettiford wished to challenge any of
the other non-vacated qualifying convictions. In response to
this order, on June 15, 2007, the Public Defender filed a mem-
orandum of law explaining that Pettiford challenged the use
of all his predicate convictions. The government filed a
response to this memorandum on July 6, 2007, arguing, inter
alia, that Pettiford was procedurally barred from challenging
the use of the three predicate convictions because these chal-
lenges "were not raised at trial or on direct appeal, and the
defendant neither offer[ed] cause excusing this failure nor
c[ould] he show prejudice from not having raised the argu-
ments." J.A. 232. As a result, in a reply, the Public Defender
clarified that for § 2255 purposes, only the two 2002 vacated
convictions should be considered, and that Pettiford’s chal-
lenges to the three remaining predicates were "not [a] part of
his habeas petition [but] instead[ ] they [were] relevant con-
siderations at a resentencing following the grant of his habeas
petition."2 J.A. 250. In other words, Pettiford asked the district
court to bifurcate the proceedings.

  On November 24, 2008, the district court granted Petti-
  2
   Later, Pettiford conceded that the 1993 conspiracy conviction qualified
as an ACCA predicate. Thus, Pettiford maintained that only the 1994 and
2001 convictions were to be considered at resentencing.
6                 UNITED STATES v. PETTIFORD
ford’s § 2255 petition and ordered that he be resentenced. The
district court granted Pettiford habeas relief because "two of
his qualifying convictions [had been] vacated after his initial
sentence." J.A. 263. The district court recognized that even
with the two 2002 drug convictions vacated, Pettiford’s
record "retain[ed] three convictions that might enhance his
sentence under § 924(e)," J.A. 266, but nevertheless granted
Pettiford a resentencing based on an "examination of [Petti-
ford’s] remaining ACCA qualifying convictions . . . akin to
what would occur at a re-sentencing proceeding," J.A. 267. In
doing so, the district court decided that Pettiford’s conviction
for Maryland assault in 2001 was not a violent felony under
the ACCA. Relying on Shepard v. United States, 544 U.S. 13
(2005), and United States v. Simms, 441 F.3d 313 (4th Cir.
2006), the district court explained that when analyzing
whether a conviction is a violent felony under the ACCA,
courts cannot consider documents "that are not incorporated
into the charging document." J.A. 269. Because the only basis
for concluding that Pettiford’s 2001 assault might be a violent
felony is found in a Statement of Probable Cause, which was
not incorporated into the charging document, the district court
concluded that the 2001 assault conviction was not a violent
felony, and thus could not be counted. Disregarding both the
2001 assault conviction and the two sentences vacated by the
Maryland state courts, the district court found "that Pettiford
has two remaining ACCA qualifying convictions . . . [and] no
longer qualifies" for an enhanced sentence under the ACCA.
J.A. 270.

   On December 8, 2008, the government filed a motion for
reconsideration, which the district court denied on January 7,
2009. Pettiford was subsequently resentenced on January 8,
2009 to 100 months in prison. This appeal followed.

                              II.

   On appeal, the government contends that the district court
erred in granting Pettiford’s § 2255 petition, because even
                      UNITED STATES v. PETTIFORD                            7
after the vacatur of Pettiford’s two drug convictions, Pettiford
still had three qualifying predicate convictions. Pettiford
responds that a defendant need only show that some of his
underlying predicate convictions were vacated to be entitled
to § 2255 relief. However, in the event we find otherwise, he
argues that his challenges to the other predicate convictions
should be considered as part of his habeas claim, and that if
he failed to challenge these convictions, that failure should be
excused because he can show cause and prejudice for the pro-
cedural default. Alternatively, he maintains he is "actually
innocent of the enhancement," and thus, the district court did
not commit error in granting the petition. Appellee’s Br. at 15.
We consider each argument in turn. In so doing, we review
legal issues de novo and factual findings under a clear error
standard. United States v. Roane, 378 F.3d 382, 395 (4th Cir.
2004).

                                     A.

   We first consider the government’s argument that the dis-
trict court erred in granting Pettiford’s § 2255 petition on the
basis of Pettiford’s two vacated convictions.3
  3
    Pettiford’s § 2255 petition maintained that he was entitled to habeas
relief solely because two of his five ACCA-predicate convictions had been
vacated. Admittedly, in his initial § 2255 petition, Pettiford did challenge
the predicate status of his 1993 drug conviction. Later, however, he clari-
fied that for § 2255 purposes only the two 2002 vacated convictions
should be considered, and that his "challenges to the three remaining pred-
icates [were simply] re-sentencing issues." J.A. 259. The district court
accepted this clarification, explaining that "Pettiford’s challenge to [the
remaining] convictions" were not "a part of his § 2255 petition." J.A. 267.
Instead, the court’s "examination of his remaining ACCA qualifying con-
victions [was] akin to what would occur at a re-sentencing proceeding,"
after § 2255 relief was granted. J.A. 267. Thus, in considering whether to
grant Pettiford’s § 2255 petition to begin with, the district court considered
only whether Pettiford was entitled to relief as a result of the vacatur of
his two state convictions.
8                    UNITED STATES v. PETTIFORD
   In Custis v. United States, 511 U.S. 485, 497 (1994), the
Supreme Court observed that if a defendant "is successful in
attacking [his] state sentences, he may then apply for reopen-
ing of any federal sentence enhanced by the state sentences."
Later, in Daniels v. United States, 532 U.S. 374, 382 (2001),
the Court again noted that if a challenge to an underlying con-
viction is successful in state court, "the defendant may then
apply for reopening of his federal sentence," but added that if
the prior conviction is no longer open to direct or collateral
attack in its own right, then the federal prisoner can do noth-
ing more about his sentence enhancement. Finally, in Johnson
v. United States, 544 U.S. 295, 310 (2005), the Court reiter-
ated the holdings of Custis and Daniels, adding, inter alia, that
from the date the district court enters judgment in the federal
case, the defendant is obliged to act diligently to obtain the
state-court order vacating the predicate conviction.

   In accordance with this line of cases, this court, when
reviewing sentences imposed under the career offender guide-
line, has concluded that sentence enhancements based on pre-
vious convictions should be reconsidered if those convictions
are later vacated. See United States v. Gadsen, 332 F.3d 224,
228 (4th Cir. 2003) (noting that a defendant may apply for a
reopening of his federal sentence once he has successfully
challenged the underlying conviction).4 Specifically, this court
has held that if a defendant "succeeds in a future collateral
proceeding in overturning his [state] conviction, federal law
enables him then to seek review of any federal sentence that
was enhanced due to his state conviction." United States v.
Bacon, 94 F.3d 158, 161 n.3 (4th Cir. 1996). Given this lan-
guage, the district court determined that Pettiford was entitled
    4
   Custis, Daniels, and Johnson apply "whether the sentence enhance-
ment was imposed because of the ACCA or because of the Sentencing
Guidelines." Gadsen, 332 F.3d at 228 n.3 (internal quotations and citation
omitted); see also United States v. Arango-Montoya, 61 F.3d 1331, 1336
(7th Cir. 1995); United States v. Jones, 27 F.3d 50, 52 (2d Cir. 1994) (per
curiam); United States v. Garcia, 42 F.3d 573, 581 (10th Cir. 1994).
                     UNITED STATES v. PETTIFORD                        9
to § 2255 relief because he had successfully challenged in
state court two state sentences that had been used to enhance
his federal sentence.

   However, as noted by the government, even without the
two vacated state convictions, Pettiford’s record retains three
convictions that support enhancing his sentence under
§ 924(e). Thus, the issue before us is whether a petitioner is
entitled to § 2255 relief after successfully attacking some of
his predicate sentences if those vacated convictions are not
necessary for the armed career criminal designation. Neither
we nor the Supreme Court have addressed this specific issue.5
And although, since Custis, several other circuits have held or
indicated that a defendant may be able to receive § 2255 relief
if he has successfully challenged in state court a state convic-
tion previously used in enhancing the federal sentence, in
each of these cases, the state sentences at issue, if vacated,
would have lowered the defendant’s conviction count below
the minimum number necessary to enhance the sentence. See,
e.g., United States v. Doe, 239 F.3d 473, 475 (2d Cir. 2001);
United States v. LaValle, 175 F.3d 1106, 1108 (9th Cir.
1999); United States v. Walker, 198 F.3d 811, 813 (11th Cir.
1999); United States v. Pettiford, 101 F.3d 199, 200 (1st Cir.
1996); Young v. Vaughn, 83 F.3d 72, 73 (3d Cir. 1996);
United States v. Cox, 83 F.3d 336, 339 (10th Cir. 1996);
United States v. Rogers, 45 F.3d 1141, 1143 (7th Cir. 1995);
United States v. Nichols, 30 F.3d 35, 36 (5th Cir. 1994).

   To determine whether Pettiford should have been awarded
habeas relief and had his sentence reopened on the ground
that two of the five convictions used to support his sentence
  5
    Custis, Daniels, and Johnson all dealt with defendants whose enhanced
sentences might have been materially impacted by the vacatur of the chal-
lenged state convictions. See Custis, 511 U.S. at 497 (attacking two of
three predicate convictions); Daniels, 532 U.S. at 374 (attacking two of
four predicate convictions); Johnson, 544 U.S. at 295 (attacking one of
two predicate convictions).
10                 UNITED STATES v. PETTIFORD
were later vacated, we must look to the language of 28 U.S.C.
§ 2255. Section 2255 provides that habeas relief should be
awarded where

     the court finds that the judgment was rendered with-
     out jurisdiction, or that the sentence imposed was not
     authorized by law or otherwise open to collateral
     attack, or that there has been such a denial or
     infringement of the constitutional rights of the pris-
     oner as to render the judgment vulnerable to collat-
     eral attack.

28 U.S.C. § 2255(b). Once the petitioner has shown this, "the
court shall vacate and set the judgment aside and shall dis-
charge the prisoner or resentence him or grant a new trial or
correct the sentence as may appear appropriate." Id. Thus, a
district court’s resolution of a prisoner’s § 2255 petition pro-
ceeds in two steps. See United States v. Hadden, 475 F.3d
652, 661 (4th Cir. 2007). First, the district court must deter-
mine whether the prisoner has met his burden of showing that
his sentence is unlawful on one of the specified grounds. Id.
Second, if the prisoner’s sentence is found unlawful on one of
those grounds, the district court should grant the prisoner an
"appropriate" remedy, which includes discharge, resentenc-
ing, or a new trial. Id. If the prisoner fails to show that his
sentence is unlawful on one of the specified grounds under the
threshold inquiry, however, "the court must deny the peti-
tion." Id.

   Pettiford cannot meet the threshold inquiry, in that he has
failed to establish any of the specified grounds for rendering
the sentence unlawful. First, he cites no precedent, nor do we
find any, suggesting that, in this situation, Pettiford was sen-
tenced in violation of the Constitution. Second, he points to
nothing in the record, nor are we able to find anything, to sug-
gest that the district court did not have jurisdiction. Third, the
sentence was authorized by law because the vacatur of the
two 2002 convictions did not render Pettiford’s ACCA sen-
                   UNITED STATES v. PETTIFORD                   11
tence invalid as a threshold matter. Section 924(e)(1) estab-
lishes a mandatory minimum sentence of fifteen years without
parole for any person convicted of a violation of 18 U.S.C.
§ 922(g) who has three or more previous convictions for a
"violent felony" or "serious drug offense." 18 U.S.C.
§ 924(e)(1). After the vacatur of the two 2002 convictions,
three predicate convictions remained in Pettiford’s record.
Thus, the statutory preconditions for sentence enhancement
were still present, and Pettiford’s sentence was still subject to
enhancement pursuant to the ACCA. Finally, we do not
believe that the sentence is "otherwise open to collateral
attack." 28 U.S.C. § 2255(a). The Supreme Court has inter-
preted the phrase "otherwise subject to collateral attack" as
involving a claim of "error of fact or law of the ‘fundamental’
character that renders the entire proceeding irregular and
invalid." United States v. Addonizio, 442 U.S. 178, 186
(1979); see also United States v. Eakman, 378 F.3d 294, 298
(3d Cir. 2004) (holding that a sentence is subject to collateral
attack if "the district court received ‘misinformation of a con-
stitutional magnitude’ and . . . the district judge relied at least
in part on that misinformation" (quoting United States v.
Spiropoulos, 976 F.2d 155, 163 (3d Cir. 1992)). There is no
evidence that Pettiford’s sentencing was constitutionally
defective or flawed in a fundamental way. Indeed, in his
habeas petition, Pettiford made no such claim.

   Instead of finding that Pettiford’s sentence was unlawful on
one of the specified grounds, the district court granted Petti-
ford § 2255 relief on the assumption that vacatur of any predi-
cate sentence automatically entitles a petitioner to habeas
relief without further inquiry. See J.A. 266 ("[T]his Court . . .
finds that Pettiford’s subsequently vacated convictions entitle
him to a re-sentencing."). This was error. Vacatur alone does
not entitle a petitioner to habeas relief. Rather, as we stated
in Bacon, vacatur entitles a petitioner to "seek review." 94
F.3d at 162 n.3. In seeking review, however, the petitioner
must still meet his burden of showing that his sentence is
unlawful on one of the specified grounds, because only after
12                    UNITED STATES v. PETTIFORD
determining that a sentence is unlawful can the district court
vacate and set aside the sentence. See Hadden, 475 F.3d at
661. Here, not only did Pettiford fail to show that his sentence
was rendered unlawful by the vacatur of his two 2002 convic-
tions, but also the district court failed to make this inquiry
before finding that Pettiford was entitled to § 2255 relief.

   Admittedly, after granting § 2255 relief, the district court
did determine that Pettiford’s sentence was unlawful. After
concluding that "Pettiford’s subsequently vacated convictions
entitle[d] him to [habeas relief]," J.A. 266, the district court
considered Pettiford’s remaining ACCA qualifying convic-
tions "akin to what would occur at a re-sentencing proceed-
ing," J.A. 267, and determined that without his 2001 assault
conviction, Pettiford’s sentence exceeded the maximum sen-
tence allowed by law because the sentence could no longer be
enhanced under the ACCA.6 In so doing, however, the district
court inverted the § 2255 process. Pursuant to Hadden, the
district court had to determine whether Pettiford’s sentence
had been rendered unlawful on one of the specified grounds
by the vacatur of his two 2002 convictions before vacating
and setting aside the sentence. See 475 F.3d at 661. By doing
otherwise, the district court bypassed the threshold inquiry of
whether Pettiford’s § 2255 petition, on its face, sufficiently
established that Pettiford’s sentence was "rendered without
jurisdiction," "imposed in violation of the Constitution or the
laws of the United States," or that it was "otherwise subject
to collateral attack." 28 U.S.C. § 2255.
  6
    The government argues that the district court committed error in allow-
ing Pettiford, after the court granted him § 2255 relief but before fashion-
ing a remedy, to argue that his remaining ACCA qualifying convictions
were not predicate offenses under the ACCA. The district court reasoned
that irrespective of whether these challenges are procedurally barred,
"[t]he more efficient rule is to permit defendants to raise such arguments
after they have had other convictions vacated and the arguments could
have an actual impact on their sentences." J.A. 267. Because we find that
the district court erred in granting Pettiford’s § 2255 motion, we need not
decide whether the district court’s consideration of these challenges, in
order to determine Pettiford’s appropriate remedy, constitutes error.
                      UNITED STATES v. PETTIFORD                           13
   The flaw in the district court’s approach is made manifest
by the fact that, by virtue of the vacated convictions, Pettiford
argued on collateral review the applicability of case law that
would not be available to others similarly situated. Below,
Pettiford argued that his 2001 assault conviction could not be
counted as an ACCA predicate because it was not a violent
felony. His argument principally relied on Shepard, 544 U.S.
at 21, in which the Supreme Court held that to determine
whether a conviction constitutes a violent felony, a court may
not go "beyond conclusive records made or used in adjudicat-
ing guilt and look[ ] to documents submitted to lower courts
even prior to charges," and on Simms, 441 F.3d at 317, in
which we held that a court may not consider documents that
are not "expressly incorporated into [the] charging docu-
ment." Relying on these cases, Pettiford argued that his 2001
assault could not be classified as a violent felony because the
only basis for such a conclusion is found in a Statement of
Probable Cause which was not incorporated into the charging
document. The district court agreed with Pettiford, citing
Shephard and Simms for support. Neither Shepard nor Simms,
however, were available to Pettiford at the time of the original
sentencing, nor have they been found to be retroactively
applicable. See United States v. Davis, 133 F. App’x 916 (4th
Cir. 2005); see also United States v. Christensen, 456 F.3d
1205, 1207-08 (10th Cir. 2006); Corey v. United States, 221
F. App’x 1 (1st Cir. 2007); United States v. Armstrong, 151
F. App’x 155, 157 (3d Cir. 2005). And, as we have noted, the
district court reached this inquiry only because it bypassed the
threshold determination of whether Pettiford’s § 2255 peti-
tion, on its face, sufficiently established that Pettiford’s sen-
tence was unlawful on one of the specified grounds.7
  7
    Furthermore, the district court’s actions effectively allowed Pettiford to
raise challenges that were procedurally barred. Pettiford could have chal-
lenged the adequacy of classifying his 1993, 1994, and 2001 convictions
as ACCA predicates at the original sentencing and on direct appeal, and
because he did not do so, those challenges are barred unless Pettiford can
"show cause and actual prejudice . . . or . . . that a miscarriage of justice
14                    UNITED STATES v. PETTIFORD
   In sum, because the district court failed to hold Pettiford to
his burden of showing that the vacated sentences rendered his
federal sentence unlawful on one of the specified grounds—a
burden the record demonstrates he could not meet—we agree
with the government that the district court erred in granting
Pettiford § 2255 relief.8

                                      B.

   Although Pettiford characterized his challenges to the
remaining three convictions as resentencing issues in the dis-
trict court, on appeal, he argues that we should consider his
challenges to the 1994 and 2001 predicate convictions as part
of his habeas petition. If we do so, he asserts that we should
find him entitled to § 2255 relief. Because Pettiford never
challenged his three remaining predicate convictions at sen-
tencing or on direct appeal, he would typically be "barred
from raising the[se] claim[s] on collateral review." Sanchez-
Llamas v. Oregon, 548 U.S. 331, 351 (2006); see also United
States v. Emanuel, 869 F.2d 795, 796 (4th Cir. 1989) (non-
constitutional issues are deemed waived in a § 2255 motion

would result from the refusal of the court to entertain the collateral attack."
United States v. Mikalajunas, 186 F.3d 490, 492-93 (4th Cir. 1999). Petti-
ford, however, was not required to show cause and prejudice or a miscar-
riage of justice because the district court accepted Pettiford’s argument
that his challenges were to be considered after the court granted him
§ 2255 relief. Effectively, the district court allowed Pettiford to forego the
burden of showing cause and prejudice or a miscarriage of justice, but
nevertheless considered Pettiford’s attacks on his 1994 and 2001 convic-
tions to determine that his sentence was unlawful. The entire § 2255 pro-
cess was therefore turned on its head.
   8
     The government also argues that should we find that the district court
properly granted Pettiford § 2255 relief, then we must find error in the dis-
trict court’s willingness to allow Pettiford to "revise unilaterally the terms
of his plea agreement," in which he affirmed, more than once, that he was
subject to an ACCA sentence. Appellant’s Br. at 27. Because we find the
district court erred in granting Pettiford’s § 2255 petition, we need not
address the binding effect of Pettiford’s plea agreement.
                      UNITED STATES v. PETTIFORD                         15
if they were not raised on direct appeal). The Supreme Court
has recognized an equitable exception to the bar, however,
when a habeas applicant can demonstrate cause and prejudice,
or actual innocence. See Dretke v. Haley, 541 U.S. 386, 393
(2004); see also Mikalajunas, 186 F.3d at 492-93. We thus
consider whether Pettiford has shown cause and prejudice, or
actual innocence, below.

                                    1.

   "In order to collaterally attack a conviction or sentence
based upon errors that could have been but were not pursued
on direct appeal, the movant must show cause and actual prej-
udice resulting from the errors of which he complains . . . ."
Mikalajunas, 186 F.3d at 492-93. "The existence of cause for
a procedural default must turn on something external to the
defense, such as the novelty of the claim or a denial of effec-
tive assistance of counsel." Id. at 493.

   Pettiford maintains that cause existed to excuse his default
because he had no legal basis to challenge the predicate con-
victions at the original sentencing.9 He explains that at the ini-
tial sentencing, his two 2002 drug convictions had not yet
been vacated, and in the absence of these reversals, he still
had three prior serious drug offenses—the two 2002 drug con-
victions and the 1993 drug conspiracy conviction—on his
record to qualify him as an armed career criminal independent
from the 2001 assault conviction and the 1994 breaking and
entering conviction. As a result, he argues, any challenge to
his ACCA status, or the underlying sentences, at his original
sentencing would have been futile.
  9
    Pettiford also explains that the prejudice suffered here is obvious. The
ACCA enhancement increased his statutory maximum penalty from ten to
fifteen years, and his sentencing guideline range from 84-105 months to
188-235 months. Because we find that Pettiford cannot show cause, we
need not determine whether Pettiford has shown sufficient prejudice. See,
e.g., Mikalajunas, 186 F.3d at 493-94 (discussing only the element of
cause). The exception requires a showing of both cause and prejudice.
16                UNITED STATES v. PETTIFORD
   As a preliminary matter, the government asserts, and our
review of the record reveals, that Pettiford never argued cause
and prejudice below. Instead, Pettiford maintained that his
challenges to the 1994 and 2001 convictions were resentenc-
ing issues, not habeas issues, and thus he was able to forego
showing cause and prejudice. In the briefs below, Pettiford’s
counsel explained, "[T]he challenges to Mr. Pettiford’s other
prior convictions are not part of his habeas petition. . . . Mr.
Pettiford has not sought to amend his habeas petition to
include these challenges." J.A. 250-51. Similarly, counsel
maintained, "[T]he criminal history challenges to the three
remaining predicates are re-sentencing issues, not habeas
claims." J.A. 259. It is settled in this circuit that failure to
present an argument to the district court constitutes waiver
before this court. United States v. Evans, 404 F.3d 227, 236
n.5 (4th Cir. 2005). Further, the Supreme Court recently held
that an argument not presented to the federal district court in
a habeas petition is forfeited and cannot be advanced at the
merits stage, on appeal. McDaniel v. Brown, 130 S. Ct. 665,
675 (2010) ("Recognizing that his . . . claim cannot prevail,
respondent tries to rewrite his federal habeas petition. His
attempt comes too late, however, and he cannot now start
over.").

   Nonetheless, assuming arguendo that Pettiford’s current
"cause" theory is properly before us, we are unable to find any
external impediments resulting in counsel’s failure to chal-
lenge the 1994 and 2001 convictions at sentencing, or on
direct appeal. On the contrary, the record shows that trial
counsel did challenge three of the eight predicate convictions
listed on the Special Report. "[A] petitioner cannot establish
cause when the facts underlying the claim were in existence
and were available upon a reasonably diligent search," Rose
v. Lee, 252 F.3d 676, 687 (4th Cir. 2001), and here, the facts
underlying Pettiford’s challenges to the 1994 and 2001 con-
victions were available at Pettiford’s sentencing.
                      UNITED STATES v. PETTIFORD                          17
   Further, Pettiford’s alleged basis for demonstrating cause
has no recognition in the law.10 See, e.g., Bousley v. United
States, 523 U.S. 614, 623 (1998) (finding that "futility cannot
constitute cause if it means simply that a claim was unaccept-
able to that particular court at that particular time" (internal
quotations and citation omitted)); Richardson v. Turner, 716
F.2d 1059, 1061 (4th Cir. 1983) (holding the same). If we
were to accept Pettiford’s argument—that cause exists to
excuse procedural default where the defendant believes that
challenging a predicate sentence would be futile—then there
would be no reason for a defendant to challenge his predicate
convictions during sentencing, unless he could attack a suffi-
cient number of sentences to bring his predicate count below
the number necessary for the enhancement. All other chal-
lenges would be handled by the courts on collateral attack,
thereby rendering meaningless our longstanding commitment
to the finality of judgments. See, e.g., Sawyer v. Whitley, 505
U.S. 333, 338 (1992) (emphasizing finality over the correc-
tion of errors); McCleskey v. Zant, 499 U.S. 467, 490-91
(1991) (same); Wainwright v. Sykes, 433 U.S. 72, 89-90
(1977) (same). We cannot agree to this. Habeas review
extracts significant costs from judicial, defense, and prosecu-
torial resources. Schneckloth v. Bustamonte, 412 U.S. 218,
259-60 (1973) (Powell, J., concurring). More importantly, as
the Supreme Court said in McCleskey, we do not want "ha-
beas corpus review [to] give litigants incentives to withhold
claims for manipulative purposes and [to] establish disincen-
tives to present claims when evidence is fresh." 499 U.S. at
491-92; see also Reed v. Ross, 468 U.S. 1, 13 (1984); Wain-
wright, 433 U.S. at 89. Instead, if an attack on a predicate sen-
tence can be raised at sentencing, that attack should be han-
dled by the sentencing judge, irrespective of whether a
successful challenge would render a sentencing enhancement
obsolete.
  10
     Nor is it clear why it would have been futile for Pettiford to challenge
the 1994 and 2001 convictions at sentencing or on direct appeal. Pettiford
filed the coram nobis petition for post-conviction relief, seeking to vacate
his two 2002 convictions, before his original sentencing took place.
18                UNITED STATES v. PETTIFORD
   Thus, because we find that Pettiford has failed to demon-
strate cause to excuse his failure to challenge the 1994 and
2001 predicate sentences at sentencing or on direct appeal, we
cannot excuse his procedural default.

                               2.

   With Pettiford having failed to demonstrate cause and prej-
udice to excuse his procedural default, the question remains
whether he can show actual innocence. Pettiford contends that
he should be granted habeas relief because he is "actually
innocent of the enhancement," Appellee’s Br. at 15, in that his
record does not have "three previous convictions . . . for a vio-
lent felony or a serious drug offense," 18 U.S.C. § 924(e)(1).
Aside from the two vacated convictions, he notes that his
2001 assault conviction could not be considered a "violent fel-
ony" for ACCA purposes, and thus, he contends, the basis for
the district court’s original ACCA finding vanished because
three ACCA predicates no longer remain.

   Our court has previously ruled that the actual innocence
exception may be applied in § 2255 to noncapital sentencing
proceedings. United States v. Maybeck, 23 F.3d 888, 892-94
(4th Cir. 1994); see also Mikalajunas, 186 F.3d at 494. To
succeed on actual innocence grounds, however, "a petitioner
must demonstrate actual factual innocence of the offense of
conviction, i.e., that petitioner did not commit the crime of
which he was convicted; this standard is not satisfied by a
showing that a petitioner is legally, but not factually, inno-
cent." Mikalajunas, 186 F.3d 494. Furthermore, the "movant
must show actual innocence by clear and convincing evi-
dence." Id. at 493.

   Pettiford’s argument on this point suffers from multiple
infirmities. To begin with, a federal sentencing proceeding is
not ordinarily an appropriate forum in which to challenge the
validity of a prior state conviction. Whether petitioner is actu-
ally innocent of a prior state offense is a claim to be tested
                       UNITED STATES v. PETTIFORD                            19
through the normal processes of trial and appeal and any
appropriate post-conviction proceedings. A federal sentencing
court cannot be expected to hold a re-trial of prior state con-
victions, and even if the resources to do so were available, a
respect for state courts would dictate that the validity of state
convictions be resolved not in federal sentencing proceedings
but in the manner that Congress and the Supreme Court have
set forth. We earlier noted that the Supreme Court in a trio of
cases has counseled against using federal sentencing proceed-
ings as a forum for collateral attacks on state convictions. See
Johnson, 544 U.S. at 303 (Congress did not intend "to make
it so easy to challenge final judgments that every occasion to
enhance a sentence for recidivism would turn a federal sen-
tencing court into a forum for difficult and time-consuming
reexaminations of stale state proceedings."); Daniels, 532
U.S. at 381-82; Custis, 511 U.S. at 496-97. In this regard, any
argument of actual factual innocence of the remaining convic-
tions has not been accepted by any court or in any forum in
which Pettiford could be expected to move to set the convic-
tion aside.

   Pettiford further misinterprets our holdings in Mikalajunas
and Maybeck. Irrespective of our holding in Mikalajunas, Pet-
tiford maintains that for purposes of proving actual innocence
in the context of eligibility for application of the ACCA,
Fourth Circuit precedent requires only that he show that the
district court erred in applying the statute. His argument prin-
cipally relies on our holding in Maybeck. In that case, the
defendant was originally sentenced as a career offender under
the Sentencing Guidelines based on two prior convictions
noted in the presentence report as crimes of violence.11 The
  11
    We recognize that Maybeck concerns the career offender provision of
the Sentencing Guidelines, and not the ACCA. Nevertheless, in Mikala-
junas, we noted that under the reasoning of Maybeck, "actual innocence
applies in . . . the context of eligibility for application of a career offender
or other habitual offender . . . provision." 186 F.3d at 495 (emphasis
added). To reach its holding, Maybeck relied on cases concerning various
20                   UNITED STATES v. PETTIFORD
defendant did not object to his classification as a career
offender at the sentencing hearing or appeal his sentence.
Later, however, the defendant filed a § 2255 petition on the
ground that he had been improperly sentenced as a career
offender; the defendant explained that he had erroneously
informed the probation officer that he had been convicted for
armed burglary, which is categorically a crime of violence
under the federal Sentencing Guidelines, when in fact he had
been convicted for attempted third-degree burglary, which is
not. The district court denied the petition, finding that the
defendant’s failure to raise his claim at his sentencing hearing
and by direct appeal constituted a procedural default.

   On appeal, however, we reversed and remanded for resen-
tencing. Specifically, we found that the defendant was actu-
ally innocent of being a career offender because he was
innocent of one of the convictions used to determine that he
was a career offender. And although we recognized that
defendant’s challenge to this predicate sentence was proce-
durally barred, we excused the misstep, noting that "it is an
unacceptable deviation from our fundamental system of jus-
tice to automatically prevent the assertion of actual innocence
simply because a defendant has not observed procedural ave-
nues available to him." 23 F.3d at 892.

   Pettiford contends that Maybeck stands for the proposition
that the actual innocence exception applies to excuse a proce-
dural default whenever a movant is "innocent" of any sentenc-
ing enhancement alleged to be error. And because, he argues,
the § 924(e) enhancement was erroneously applied to him, he

habitual offender statutes. See 23 F.3d at 893. We see little difference
between holding that a defendant can be innocent of the acts required to
enhance a sentence under the Sentencing Guidelines and applying a paral-
lel rationale in cases concerning the ACCA. See id. (noting that "[i]n non-
capital enhancement cases, the length of a defendant’s sentence may be
aggravated by factors specified by statute or the Guidelines").
                      UNITED STATES v. PETTIFORD                         21
concludes that he is "actually innocent" of that adjustment.
We disagree.

   Pettiford misinterprets our holding in Maybeck. We granted
relief in Maybeck because the defendant clearly showed that
he had not committed the crime on which the calculation of
his sentence was based. See id. at 894 ("There is no dispute
. . . that [the defendant] was innocent of one of the convic-
tions used to determine that he was a career offender and he
was improperly sentenced as such."). It was uncontested that
the defendant in Maybeck had not committed one of the
underlying predicate convictions. See id. at 892 n.7 ("The par-
ties do not dispute that [defendant] was not convicted of
armed burglary in 1973."); see also Mikalajunas, 186 F.3d
494 (finding that a petitioner is factually innocent if he shows
that he "did not commit the crime of which he was con-
victed"). The defendant’s sentence was therefore erroneously
enhanced by an armed burglary conviction that he simply did
not have.

   Pettiford, by contrast, makes no suggestion whatsoever that
he did not actually commit the 2001 assault. Rather, he makes
the legal argument that this conviction should not have been
classified as a "violent felony" under the ACCA.12 This argu-
ment, even after Maybeck, is not cognizable as a claim of
actual innocence. See Mikalajunas, 186 F.3d at 495 (limiting
Maybeck to its facts and finding that actual innocence does
not extend to non-factual challenges to the application of sen-
tencing enhancements); see also Poindexter v. Nash, 333 F.3d
372, 381-82 (2d Cir. 2003) (rejecting a claim of actual inno-
cence, premised on the argument that defendant’s three con-
victions should have been treated as a single conviction
  12
     Likewise, the two 2002 convictions were vacated on legal, rather than
factual, grounds. They were vacated not because Pettiford did not commit
the crimes, but instead because the state court "imposed an invalid period
of incarceration as a condition of probation, and that sentence [was] irrec-
oncilable with the terms of [Pettiford’s] plea agreement." J.A. 186.
22                     UNITED STATES v. PETTIFORD
because he was sentenced for all three convictions on the
same date, because such an argument is legal, not factual, and
thus "not cognizable as a claim of actual innocence"). Under
the reasoning of Maybeck, actual innocence applies in the
context of habitual offender provisions only where the chal-
lenge to eligibility stems from uncontested actual innocence
of the predicate crimes, and not from the classification of the
predicate crimes. See 23 F.3d at 894 (noting that in extending
actual innocence to the habitual offender context, our objec-
tive is to "protect[ ] defendants from sentencing based on ele-
ments of crimes for which they are conclusively innocent").

  Thus, we find that Pettiford cannot demonstrate actual
innocence to excuse his procedural default. Maybeck does not
excuse his failure to challenge his remaining qualifying predi-
cates at sentencing or on direct appeal.13

                                     III.

   In conclusion, we hold that the district court erred in grant-
ing Pettiford’s § 2255 petition, because Pettiford did not
show, nor could he show, that the vacated sentences alone
rendered his federal sentence unlawful on one of the specified
grounds. We also hold that by failing to challenge his remain-
ing predicate sentences at sentencing or on direct appeal, Pet-
tiford procedurally defaulted on his claim that the district
court improperly enhanced his sentence under the ACCA.
Finally, we hold that under Maybeck, actual innocence applies
in the context of habitual offender provisions only where the
challenge to eligibility stems from actual innocence of the
predicate crimes. Accordingly, we reverse and remand this
  13
     The government also argues that, irrespective of our understanding of
Maybeck, Pettiford would not be entitled to relief because his challenge to
the 2001 assault conviction is predicated on case law that was not avail-
able to Pettiford at the original sentencing, or that is retroactively applica-
ble. Because we find that Pettiford cannot demonstrate actual innocence
to excuse his procedural default, we need not address this argument.
                  UNITED STATES v. PETTIFORD                 23
case to the district court with instructions to reinstate Petti-
ford’s original sentence.

     REVERSED AND REMANDED WITH INSTRUCTIONS
