Vacated and remanded by published opinion. Judge KING wrote the opinion, in which Judge MOTZ joined. Judge NIEMEYER wrote an opinion concurring in the judgment.
KING, Circuit Judge.Defendants Owen Robinson, Kendall Schuyler, and William Parros (collectively, the “Defendants”) have appealed the sentences imposed on them in 2003 in the District of Maryland. This is the third separate occasion for our Court to review sentences the Defendants received on their jury convictions in 1999 for various offenses relating to a large drug trafficking conspiracy, centered in the area of Baltimore, Maryland. The district court initially sentenced the Defendants in March 2000: Robinson and Schuyler each received life in prison, and Parros received thirty years. The Defendants promptly appealed their sentences to this Court (the “First Appeals”) and, in November 2001, we vacated and remanded for resentencing under Apprendi v. New Jersey, 530 U.S. 466, 120 S.Ct. 2348, 147 L.Ed.2d 435 (2000). See United States v. Johnson, 26 Fed.Appx. 111, 2001 WL 1349205, at *3 (4th Cir. Nov.2, 2001) (hereinafter “Robinson /”). The Defendants were resentenced by the district court in May 2003, and they thereafter again appealed their sentences to this Court (the “Second Appeals”). By opinion filed in December 2004, we rejected their new contentions of sentencing error and affirmed their 2003 sentences. See United States v. Robinson, 390 F.3d 833, 838 (4th Cir.2004) (hereinafter “Robinson II”). In January 2005, the Supreme Court issued its landmark sentencing decision in United States v. Booker, 543 U.S. 220, 125 S.Ct. 738, 160 L.Ed.2d 621 (2005). Subsequently, in *553April 2005, the Court granted the Defendants’ petitions for certiorari, vacated our decision in Robinson II, and remanded the Second Appeals for further consideration in light of Booker. See Robinson v. United States, 544 U.S. 971-72, 125 S.Ct. 1875, 161 L.Ed.2d 719 (2005) (mem.).
In Booker, the Court held, inter alia, that a sentencing court commits Sixth Amendment error if it engages in judicial factfinding, under mandatory Sentencing Guidelines, that results in a sentence exceeding the maximum term authorized by the jury verdict alone. See 543 U.S. at 245-46, 125 S.Ct. 738. As explained below, we reject the contention that the Defendants’ constitutional Booker claims are subject to plain error review. The Defendants properly preserved their claims of Sixth Amendment Booker error at their resentencing proceedings in 2003 by raising timely objections under Apprendi, and their contentions here are subject to review for harmless error. And because the district court committed constitutional Booker error in its 2003 resentencing proceedings, and that error was not harmless beyond a reasonable doubt, we are obliged to vacate the Defendants’ 2003 sentences and remand.
I.
A.
On November 23, 1999, a jury in the District of Maryland convicted the Defendants and three of their co-defendants of various drug-related offenses, including conspiracy to distribute cocaine base (commonly known as “crack cocaine”), in violation of 21 U.S.C. § 846. See Robinson I, 26 Fed.Appx. 111, 2001 WL 1349205, at *1 (4th Cir. Nov.2, 2001). The essential facts underlying the Defendants’ convictions were summarized by us in Robinson I as follows:
[The Defendants] are former members of a drug trafficking conspiracy based predominantly in the O’Donnell Heights area of southeast Baltimore. That conspiracy ... distributed primarily cocaine base, but also sold powder cocaine, heroin, and marijuana. At the height of the conspiracy, [the Defendants] required weekly trips to New York to obtain kilogram quantities of powder cocaine, which they would cook into cocaine base, in order to supply their operation. The volume and profit of the organization was matched by its ruthlessness, however, as at least two individuals were killed as part of the organization’s attempt to secure control over its areas of distribution.
Id. In addition to finding each of the Defendants guilty of conspiracy to distribute crack cocaine, in contravention of § 846, the jury convicted Robinson on a separate count of possessing crack cocaine with intent to distribute, in violation of 21 U.S.C. § 841(a)(1), and Schuyler for carrying a firearm in connection with a drug trafficking offense, in violation of 18 U.S.C. § 924(c).
At the Defendants’ initial sentencing proceedings, conducted in March 2000, the district court determined that each of the Defendants’ criminal activity involved 1.5 kilograms or more of cocaine base, and thus assigned each of them a base offense level of 38 under the then-mandatory Sentencing Guidelines. With respect to Robinson, the court enhanced his offense level an additional two levels for possession of a firearm, see USSG § 2D1.1(b)(1) (1999), two levels for his leadership role in the offense, see id. § 3B1.1(c), and two levels for obstructing justice by committing perjury at trial, see id. § 3C1.1, for a total of six enhancement levels. The court sentenced Robinson to life in prison for his § 846 conspiracy conviction, and to a separate concurrent life sentence for his § 841 conviction. With respect to Schuyler, the court applied a two-level enhancement for *554his leadership role in the offense, see USSG § 3B1.1(c), plus a two-level enhancement for obstruction of justice, see id. § 3C1.1, for a total of four enhancement levels. The court also applied the murder cross-reference against Schuyler, which carries a mandatory life sentence, for his having possessed a firearm that had been used in a murder carried out by a co-defendant. See id. §§ 2A1.1, 2D1.1(d). As a result, the court imposed a life sentence on Schuyler for his § 846 conspiracy conviction, plus a consecutive sentence of five years for his § 924(c) conviction. With respect to Parros, the court imposed a sentence of thirty years for his § 846 conspiracy conviction.
After the Defendants noted their First Appeals to this Court, but before they filed appellate briefs, the Supreme Court rendered its decision in Apprendi v. New Jersey, 530 U.S. 466, 120 S.Ct. 2348, 147 L.Ed.2d 435 (2000). In Apprendi, the Court held that the Sixth Amendment requires that any fact, other than a prior conviction, that “increases the penalty for a crime beyond the prescribed statutory maximum must be submitted to a jury, and proved beyond a reasonable doubt.” Id. at 490, 120 S.Ct. 2348.
In their First Appeals, the Defendants asserted, as relevant here, that their sentences had been imposed in contravention of Apprendi, in that they each exceeded the applicable statutory maximum. These assertions were premised on the fact that the indictment did not allege, and the jury had not found, any of the threshold drug quantities necessary to authorize the sentences imposed.1 As the Defendants had not asserted Apprendi-type error during their initial sentencing proceedings, and they had been sentenced prior to Apprendi being decided, we reviewed their sentencing contentions in Robinson I for plain error only. See 2001 WL 1349205, at *2. As . we explained there, “[ujnder § 841(b)(1)(C), a defendant whose indictment for a violation of § 841(a) does not describe the quantities of drugs involved may receive a [maximum] sentence of twenty years,” or “a maximum of thirty years where the defendant has one or more prior felony convictions.” Id. The Defendants had each received sentences in March 2000 in excess of the relevant statutory máximums. Id. at *3. In addressing their contentions in the First Appeals, we concluded in Robinson I that
[t]he life sentences imposed on Schuyler and Robinson are in excess of the thirty-year statutory maximum2 ... demonstrating error that is plain.... Likewise, because the Government did not include Parros in its pre-trial § 851 information, only the twenty-year maximum of § 841(b)(1)(C) was authorized as to him. See § 851. With respect to the third prong of the plain error inquiry, we have found that a sentence in excess of the authorized statutory maximum to *555which a defendant would not otherwise be subject affects his substantial rights. Id. Finally, we recently determined that where the sentence imposed is defective due to a fatal error in the indictment, as is the case here, this court should notice that error. United States v. Cotton, 261 F.3d 397 (4th Cir.2001).
Id. at *3. Under the rationale of our Cotton decision, on which we relied in Robinson I, the Defendants’ sentences in excess of the statutory máximums constituted plain error requiring correction on appeal, because such error “seriously affect[ed] the fairness, integrity or public reputation of judicial proceedings.” Cotton, 261 F.3d at 406. Accordingly, in disposing of their First Appeals, we vacated the sentences imposed on the Defendants in 2000 and remanded for resentencing at or below the relevant statutory máximums, as established by § 841(b)(1)(C). See Robinson I, 2001 WL 1349205, at *3.
B.
While the Defendants were awaiting re-sentencing in the district court following our remand in Robinson I, the Supreme Court granted certiorari in Cotton, and the district court postponed the Defendants’ resentencing proceedings pending the Court’s decision. Ultimately, the Supreme Court reversed our decision in Cotton, holding that an unpreserved Apprendi error need not be corrected on plain error appellate review if the trial evidence of the allegations missing from the indictment was “overwhelming” and “essentially un-controverted.” United States v. Cotton, 535 U.S. 625, 633, 122 S.Ct. 1781, 152 L.Ed.2d 860 (2002) (citation omitted).
The Defendants were resentenced in the district court on May 23, 2003. At their resentencing proceedings, each of them asserted that, under Apprendi, their sentences could not be enhanced based on facts found by the court, rather than the jury. See J.A. 195 (Schuyler asserted in his 2003 sentencing memorandum that, under Apprendi he is “entitled to a jury determination” of drug quantity “beyond a reasonable doubt,” rather than judicial factfinding (internal quotation marks omitted)); J.A. 240-13, 255-56 (Schuyler maintained at 2003 sentencing hearing that jury had not determined drug quantity, as required for enhanced sentence under Apprendi); J.A. 203-06 (Parros adopted Schuyler’s sentencing memorandum and asserted at 2003 hearing that jury did not find quantity of drugs necessary for enhanced sentence); J.A. 276-77 (Robinson contended at hearing that jury did not determine requisite drug quantities for enhanced sentence).3 The district court overruled the Defendants’ Apprendi contentions, and, in reliance on the Court’s reasoning in Cotton, found that the trial evidence of drug quantities was overwhelming and uncontroverted. The court further found that each of the Defendants was responsible for at least fifty grams of cocaine base, and that their conspiracy involved “distributing more than 1.5 kilograms of crack cocaine.” J.A. 266. Accordingly, in May 2003, the court resentenced the Defendants to the identical sentences it had imposed in 2000.
C.
In June 2003, by way of their Second Appeals, the Defendants challenged their 2003 sentences, contending, as relevant here, that the district court had erred in dismissing their Apprendi objections, and that the evidence against them was neither overwhelming nor uncontroverted. The *556Defendants also sought relief (by way of a supplemental brief) under the new authority of Blakely v. Washington, 542 U.S. 296, 124 S.Ct. 2531, 159 L.Ed.2d 403 (2004), where the Court held that the Sixth Amendment was contravened by mandatory state sentencing procedures that permitted the use of judicial factfinding to increase sentence máximums.4 By our decision in Robinson II, filed on December 13, 2004, we rejected the Defendants’ Apprendi contentions in the Second Appeals and affirmed the district court’s 2003 sentences. See 390 F.3d 833, 838 (4th Cir.2004).5
Soon thereafter, on January 12, 2005, the Supreme Court issued its decision in United States v. Booker, utilizing the principles of Apprendi to invalidate the mandatory Sentencing Guidelines under which the Defendants were resentenced in 2003. See 543 U.S. 220, 244, 125 S.Ct. 738, 160 L.Ed.2d 621 (2005). In order to cure the Guidelines’ constitutional infirmity, the Court excised the statutory provisions making the Guidelines mandatory, thereby rendering them advisory only. Id. at 245, 125 S.Ct. 738. The principles of Booker were then to be applied to all cases on direct review. Id. at 268, 125 S.Ct. 738. On April 18, 2005, the Court granted the Defendants’ petitions for certiorari, and vacated and remanded our decision in the Second Appeals in Robinson II “for further consideration in light of [Booker].” Robinson v. United States, 544 U.S. 971-72, 125 S.Ct. 1875, 161 L.Ed.2d 719 (2005) (mem.). Accordingly, the Defendants’ sentences are now before us for the third time.
II.
In the present proceedings, on remand from the Supreme Court, the Defendants contend that the sentencing court committed Sixth Amendment Booker error in imposing their 2003 sentences. The Defendants assert that these sentences were impermissibly based upon quantities of drugs, found by the sentencing judge only, which were neither charged in the indictment nor proven to the jury beyond a reasonable doubt. We begin by ascertaining the applicable standard of review.
*557In a criminal appeal, the appropriate standard of review generally depends upon whether an appellant has properly preserved a claim of error by asserting a timely objection in the court below — that is, whether the error was “brought to the [district] court’s attention.” Fed.R.Crim.P. 52(b). If an appellant has timely objected, his assertion of error has been preserved, and we are obliged to apply the “harmless error” standard provided by Federal Rule of Criminal Procedure 52(a). See United States v. Olano, 507 U.S. 725, 731-32, 113 5.Ct. 1770, 123 L.Ed.2d 508 (1993). Under the harmless error standard, “[a]ny error ... that does not affect substantial rights must be disregarded.” Fed. R.Crim.P. 52(a). If an appellant failed to timely object to an alleged error, however, we are obliged to apply the “plain error” standard set forth in Rule 52(b). See Olano, 507 U.S. at 731, 113 S.Ct. 1770. Under the plain error standard, a court of appeals may correct (1) an error, (2) that is plain, and (3) that affects a defendant’s substantial rights, but only if (4) the error seriously affects the fairness, integrity, or public reputation of judicial proceedings. See id. at 732, 113 S.Ct. 1770; United States v. Rodriguez, 433 F.3d 411, 414-15 (4th Cir.2006). Although subsections (a) and (b) of Rule 52 contemplate the same inquiry into an error’s effect on substantial rights, an appellant on plain error review bears the burden of persuasion with respect to prejudice. See Rodriguez, 433 F.3d at 416. Under harmless error review, however, it is the Government that bears the burden of establishing that error was harmless. See id. Thus, we must, as a threshold matter, ascertain whether the constitutional Booker error now complained of by the Defendants was properly preserved in the district court.
As we have recognized, a defendant who was sentenced prior to the Court’s 2005 Booker decision has properly preserved a claim of Booker error if he “plainly notified the court of his position that he was being sentenced illegally, and he identified the line of Supreme Court precedent upon which he now relies.” Rodriguez, 433 F.3d at 416 (recognizing that claim of statutory Booker error has been preserved by raising timely Blakely objection at sentencing). Thus, by objecting at sentencing under the rationale of Apprendi, the primary precedent upon which Booker relied, a defendant has properly preserved a claim of Booker error. See United States v. Sullivan, 455 F.3d 248, 2006 WL 1891792, slip op. at 26 (4th Cir. July 11, 2006) (King, J., concurring) (concluding for panel majority that defendants preserved statutory Booker error by objecting on basis of Apprendi at sentencing); see also United States v. Ahtonakopoulos, 399 F.3d 68, 76 (1st Cir.2005) (recognizing that Booker error is preserved if defendant below asserted Apprendi error); United States v. Tupone, 442 F.3d 145, 157 (3d Cir.2006) (same).
Here, the Defendants interposed no objections at their sentencing proceedings in March 2000 on the basis of Apprendi or Blakely, because the Supreme Court had not yet rendered either of those decisions.6 Thus, in Robinson I, we were obliged to review the Defendants’ contentions of Apprendi error regarding their 2000 sentences for plain error. See 26 Fed.Appx. 111, 2001 WL 1349205, at *2 (4th Cir. Nov.2, 2001). In these appeals, however, we are reviewing their 2003 sentences imposed by the district court at the *558Defendants’ resentencing proceedings. And, in those proceedings, each Defendant objected, under Apprendi, to the judicial factfinding utilized in their 2003 sentencing proceedings. Thus, each Defendant “plainly notified the court of his position that he was being sentenced illegally, and [] identified the line of Supreme Court precedent upon which he now relies.” See Rodriguez, 433 F.3d at 416. Accordingly, the Defendants have properly preserved their claims of Sixth Amendment Booker error regarding their 2003 sentences, and we are now obliged to review their Booker contentions for harmless error.7
III.
The Defendants contend that the district court committed Sixth Amendment Booker error in predicating their 2003 sentences upon quantities of cocaine base found by the sentencing judge only, which were neither charged in the indictment nor proven to the jury beyond a reasonable doubt. The Government contends, on the other hand, that the Defendants’ sentences should be affirmed because any Booker error committed in the 2003 resentencing proceedings was harmless, and because the evidence of the drug quantities involved was both overwhelming and uncon-troverted.
In assessing a contention of Sixth Amendment Booker error under harmless error review, we are obliged to determine (1) whether such an error occurred, and (2) if so, whether it affected the defendant’s substantial rights. See United States v. Shatley, 448 F.3d 264, 266-67 (4th Cir.2006). As we have recently explained, a sentencing court has committed Sixth Amendment error when, “operating under a pre-Booker mandatory guidelines regime,” it has engaged in judicial fact-finding resulting in a sentence that “exceeds the maximum guideline sentence authorized by the jury verdict alone.” United States v. Smith, 441 F.3d 254, 271 (4th Cir.2006) (citing United States v. Hughes, 401 F.3d 540, 547-49 (4th Cir.2005)). And such a Sixth Amendment error affects a defendant’s substantial rights unless the Government can “prove beyond a reasonable doubt” that the error was harmless — that is, that “the court would have imposed the same sentence in the absence of the constitutional error.” See Shatley, 448 F.3d at 267.
In resentencing the Defendants in May 2003, the district court found each of the Defendants to be responsible for at least fifty grams of cocaine base, and also found that their conspiracy involved “distributing more than 1.5 kilograms of crack cocaine.” J.A. 266. Having found that “overwhelming” and “uncontroverted” evidence supported the sentences it had imposed in March 2000, the court reimposed the same sentences on the Defendants. Based solely on its findings on drug quantities, the court increased each of the Defendants’ base offense levels from 12 (the *559applicable offense level for an indeterminate quantity of cocaine base) to 38. Moreover, the court enhanced the Defendants’ various sentences based on findings regarding such factual issues as leadership role, obstruction of justice, possession of a firearm, and responsibility for an uncharged murder. Absent this judicial fact-finding, the maximum sentences the Defendants could have received under the Guidelines would have been less than those actually imposed.8 Thus, the Defendants have sufficiently established that Sixth Amendment Booker error occurred with respect to their 2003 sentences, and they are entitled to relief unless the Government can prove beyond a reasonable doubt that they would have received' the same sentences absent the Sixth Amendment error. And, as explained below, the Government is unable to make such a showing here.
First, the Government maintains that the district court can (and likely will) impose the same sentences on remand, under an advisory Guidelines regime, because it has already sentenced the Defendants to their respective sentences on two separate occasions. As we have heretofore explained, however, whether a court, on remand, may impose the same sentence under an advisory Guidelines regime is irrelevant to the assessment of a Sixth Amendment error’s effect on a defendant’s substantial rights. See Hughes, 401 F.3d at 552 (recognizing that possibility that defendant will receive same sentence under Booker remedial scheme of advisory Guidelines is not relevant to assessment of whether defendant has demonstrated prejudice from Sixth Amendment violation).9
Second, the Government contends that two of the Defendants — Parros and Schuyler — would have received the same sentences absent the Sixth Amendment Booker error. With respect to Parros, the Government maintains that he would have received the same sentence because he was designated in the presentence report (the “PSR”) as a career offender. In re-sentencing Parros in 2003, however, the court made no mention of sentencing him as a career offender. Rather, the court explicitly based Parros’s sentence upon its finding of a drug quantity (1.5 kilograms of cocaine base) corresponding to an offense level of 38. See J.A. 209. In any event, even if Parros were sentenced as a career offender, as the Government would have it, his maximum Guidelines sentence would have been 327 months, less than the 360 months (thirty years) imposed on him in 2003. Thus, even if Parros could have been sentenced as a career offender, that fact would not render the court’s Sixth Amendment error harmless.
The Government also contends that Schuyler would have received a life sentence, absent the Sixth Amendment error, because the cross-reference for murder, pursuant to USSG §§ 2A1.1, 2D1.1(d) (2002), carries a mandatory sentence of life. In finding Schuyler guilty of the illegal possession of a firearm, however, the jury did not thereby also find that he had committed a murder. The application of the murder cross-reference to Schuyler *560was thus predicated upon judicial fact-finding and, because it increased Schuyler’s sentence above the Guidelines maximum otherwise authorized by the jury’s verdict, it also contravened Booker. See United States v. Gray, 405 F.3d 227, 243-44 (4th Cir.2005) (recognizing Sixth Amendment error where judicial factfinding increased sentence by way of murder cross-reference). Thus, far from rendering the sentencing court’s Booker error harmless as to Schuyler, application of the murder cross-reference in his 2003 sentencing constituted Sixth Amendment error as well.
Finally, the Government maintains, in reliance on the Supreme Court’s holding in United States v. Cotton, 535 U.S. 625, 122 S.Ct. 1781, 152 L.Ed.2d 860 (2002), that we should disregard the Sixth Amendment Booker error in the Defendants’ 2003 resentencing proceedings because the evidence regarding the drug quantities involved in their conspiracy was both “overwhelming” and “uncontroverted.” The Cotton principles, however, are applicable only on plain error review, and we are reviewing the Defendants’ 2003 sentences for harmless error. See United States v. Smith, 441 F.3d 254 (4th Cir.2006) (applying Cotton principles to Booker claim on plain error review). Thus, because Cotton is inapplicable here, this final contention also fails.10
The Government is thus unable to meet its burden of establishing that the constitutional Booker errors in the Defendants’ 2003 resentencing proceedings were harmless beyond a reasonable doubt. As a result, their 2003 sentences must be vacated, and we are obliged to remand for resentencing. See Hughes, 401 F.3d at 546.11
IV.
Pursuant to the foregoing, we vacate the Defendants’ sentences and remand for such other and further resentencing proceedings as may be appropriate.
VACATED AND REMANDED.
. Under the drug conspiracy statute codified in § 846, a defendant convicted under that section “shall be subject to the same penalties as those prescribed for the offense, the commission of which was the object of the attempt or conspiracy.” Because the Defendants were convicted of conspiracy to distribute an indeterminate amount of-cocaine base, in violation of § 841(a), the applicable penalties are found in § 841(b)(1)(C). Under that provision, the maximum authorized penalties are a term of imprisonment of twenty years, or, if a defendant has a prior conviction for a felony drug offense, thirty years, subject to appropriate notice of the Government’s intention to use such a prior conviction to enhance a sentence being provided pursuant to § 851.
. We note that, prior to Schuyler's 2003 re-sentencing hearing, the Government submitted a sentencing memorandum to the district court conceding that the statutory maximum for his § 846 conspiracy conviction was twenty years, in that it had failed to properly serve Schuyler with notice under § 851.
. Our citations to "J.A._” refer to the contents of the Joint Appendix, filed by the parties in these appeals.
. The Blakely decision had not been issued by the Supreme Court when the Defendants filed briefs in the Second Appeals in October 2003. After Blakely was decided on June 24, 2004, the Defendants sought and received leave to file a supplemental brief raising their Blakely contentions. We rejected their claims under Blakely in a separate order, issued on August 18, 2004, pursuant to our decision in United States v. Hammoud, 381 F.3d 316, 353 (4th Cir.2004) (en banc) (holding that Blakely did not apply to Guidelines). Hammoud was subsequently overruled by Booker.
. In Robinson II, we incorrectly asserted, as a factual matter, that the Defendants had not objected on Apprendi grounds to their 2003 sentences. See 390 F.3d 833, 837 (4th Cir.2004). And, based on our misapprehension of the facts, we analyzed their Apprendi claims in the Second Appeals for plain error. Id. Our decision in Robinson II has since been vacated by the Supreme Court and is no longer controlling. See Amelkin v. McClure, 330 F.3d 822, 828 (6th Cir.2003) (recognizing that decision vacated by Supreme Court is not controlling). Having now recognized that the Defendants properly objected at their 2003 resentencing proceedings, moreover, it would be unjust for us to repeat such a factual error. See, e.g., United States v. Noble, 299 F.3d 907, 910 (7th Cir.2002) (reversing previous decision ''[i]n light of this panel's mistake” on factual issue that revealed panel’s "earlier holding was wrong”). As aptly observed by John Adams, during his defense of British soldiers charged with the Boston Massacre, "[fjacts are stubborn things ... and whatever may be our wishes, our inclinations, or the dictums of our passions, they cannot alter the state of facts and evidence.” David McCullough, John Adams 52 (Simon & Schuster 2001).
. The Defendants were initially sentenced in March 2000, and Apprendi was decided on June 26, 2000. They were resentenced in May 2003, and Blakely was decided on June 24, 2004.
. To be sure, the parties have assumed and asserted in the Second Appeals that the Defendants' contentions on their 2003 sentences should be reviewed by us for plain error. We are not, however, bound by the parties' views of such an issue, particularly when those views conflict with the facts or the law. "[O]ur judicial obligations compel us to examine independently the errors confessed.” Young v. United States, 315 U.S. 257, 258-59, 62 S.Ct. 510, 86 L.Ed. 832 (1942); see also United States v. Mackins, 315 F.3d 399, 406 & n. 3 (4th Cir.2003) (engaging in extended assessment of proper standard of review even though defense counsel assumed that review was for plain error); United States v. Vontsteen, 950 F.2d 1086, 1091 (5th Cir.1992) (en banc) ("The parties' failure to brief and argue properly the appropriate standard may lead the court to choose the wrong standard. But no party has the power to control our standard of review.”); 5 C.J.S. Appeal and Error § 748 ("[CJoncession of a point on appeal is by no means dispositive of a legal issue.”).
. Under the Guidelines, absent any judicial factfinding, the base offense level of 12 would have resulted in the following maximum potential sentences under § 846: Robinson (27 months); Schuyler (33 months); and Parros (37 months).
. We recently recognized, in United States v. Shatley, that the Government carries its burden of demonstrating that a constitutional Booker error is harmless beyond a reasonable doubt where "the district court announced an alternative nonguideline sentence under 18 U.S.C. § 3553(a) identical to the Guidelines sentence.” See 448 F.3d at 267. Because the court announced no such alternative sentences in the 2003 resentencing proceedings, Shatley is inapplicable here.
. Just as Cotton does not apply to our review of the Defendants' 2003 sentences, the district court erroneously applied Cotton when imposing those sentences. As explained above, each of the Defendants interposed objections under Apprendi, thus preserving their claims of Sixth Amendment error. We note that the district court erroneously applied Cotton when resentencing the defendants in 2003. The Cotton holding applies only to appellate standards of review; it has no bearing on a district court’s resentencing decision. Thus, on remand, the district court should resen-tence the Defendants at or below their relevant statutory máximums, as established solely by the facts alleged in the indictment and found by the jury.
. In their supplemental briefs, submitted to us following remand from the Supreme Court, the Defendants advance an additional contention raised in Robinson II — that, under the "mandate rule,” the district court lacked any authority to postpone their resentencing proceedings to await a Supreme Court decision. We rejected that contention in Robinson II, and we are content to do so again here.