dissenting.
I respectfully dissent. The majority has invoked a legal technicality in order to affirm an illegal and unjustifiedly severe sentence. The majority’s reliance on waiver totally ignores the Supreme Court’s opinion in United States v. Olano, 507 U.S. 725, 113 S.Ct. 1770, 123 L.Ed.2d 508 (1993). In addition, the district court and this court lack the authority to impose an illegal sentence.
I. Illegality of the Sentence
The majority holds that Harrison waived his right to object to his sentence, which was imposed under the retroactive application of a 2003 Guideline in violation of the Ex Post Facto Clause. The majority concludes Harrison is therefore barred from pursuing such an argument on appeal. However, the constitutional directive contained in the Ex Post Facto Clause cannot be waived. The Constitution orders Congress (and the states) that “[n]o Bill of Attainder or ex post facto Law shall be passed.” U.S. Const. Art. I, § 9, cl. 3; see also id. at § 10, cl. 1. Accordingly, the U.S. Sentencing Commission, which crafted the Sentencing Guidelines pursuant to Congress’ delegated authority, created U.S.S.G. § 1B1.11. This Guideline tells the federal courts to
use the guidelines manual in effect on the date that the defendant is sentenced, unless the court determines that this would violate the ex post facto clause of the United States Constitution, in which case it is to use the manual in effect on *810the date that the offense of conviction was committed. Because an amendment to a Sentencing Guideline has the potential to increase a defendant’s punishment for a crime committed prior to the amendment, the ex post facto clause is violated if a defendant is sentenced under the Guidelines in effect at the time of sentencing when those Guidelines produce a sentence harsher than one permitted under the Guidelines in effect at the time the crime is committed.
United States v. Frank, 354 F.3d 910, 926 (8th Cir.2004) (internal citations and quotation marks omitted); see also U.S.S.G. § 1A1.1 (identifying the statutory authority for creation of the Guidelines); Miller v. Florida, 482 U.S. 423, 435-36, 107 S.Ct. 2446, 96 L.Ed.2d 351 (1987) (wherein a unanimous Supreme Court held that a revised state sentencing guideline was void as applied to the defendant, whose offense occurred before the revised law’s effective date).
The Ex Post Facto Clause enshrines a constitutional mandate that is binding upon Congress and, by extension, the Sentencing Commission and all courts attempting to implement the Guidelines. It is not a mere “procedural” right that can be shed carelessly. See United States v. Groves, 369 F.3d 1178, 1182 (10th Cir.2004) (reversing and remanding a defendant’s sentence under the Guidelines on ex post facto grounds because a “sentencing court is not authorized to impose an unconstitutional sentence — such as a sentence that violates the Ex Post Facto Clause — and such a sentence is therefore illegal”); see also United States v. Lightsey, 886 F.2d 304, 305 (11th Cir.1989) (same).
While it is well-settled that an individual can waive his or her appellate rights in exchange for the benefits of a plea agreement, see, e.g., United States v. Garrido, 995 F.2d 808, 814 (8th Cir.1993), a court never possesses the authority to impose an illegal sentence that violates the Ex Post Facto Clause, even where a defendant agrees to the illegal sentence in the plea agreement. See United States v. Michelsen, 141 F.3d 867, 872 & n. 3 (8th Cir.1998) (recognizing that, notwithstanding a voluntary and knowing waiver of appellate rights, a defendant implicitly preserves his or her right to appeal a sentence on grounds of illegality).5 If this were not *811true, then parties could agree to illegal contracts.6
If the sentencing court applied the wrong Guideline resulting in a harsher sentence than the correct Guideline would have imposed,7 then Harrison’s sentence violates the Ex Post Facto Clause and is illegal, and the sentencing court lacked the authority to impose the sentence.
Accordingly, I would vacate the sentence and remand for resentencing pursuant to the Guidelines that were in effect at the time Harrison committed the offense.
II. Analysis Under Federal Rule of Criminal Procedure 52(b)
The majority opinion holds that Harrison waived the ex post facto argument. This is clearly wrong. The majority in so holding contradicts the principles of Olano.
Under Fed.R.Crim.P. 52(b), a court of appeals has the power to address errors to which a party did not object in district court. See Olano, 507 U.S. at 731, 113 5.Ct. 1770. This power is limited; an appellate court may only correct the alleged error that occurred below if that error (a) is plain, (b) affects substantial rights, and (c) was inadvertently forfeited. Id. at 732,113 S.Ct. 1770.
A. Forfeiture Versus Waiver
As the Olano court explained, “forfeiture is the failure to make the timely assertion of a right,” whereas “waiver is the ‘intentional relinquishment or abandonment of a known right.’ ” Id. at 733, 113 S.Ct. 1770 (citations omitted). Olano states clearly that waiver must be the product of intent. Id. Yet, in response to the Government’s comment that the Ex Post Facto Clause is inapplicable to the Guidelines, the district court itself stated on the record, “Well, it hasn’t been — it hasn’t been raised. But I toss it out for those who are intellectually hungry.” Tr. at 21 (emphasis added). This statement from the district court judge is definitive. The majority reasons that because the “judge ... explicitly raises the ex post facto argument in open court,” see supra majority opinion at 3, then it can ignore the judge’s subsequent statement that the Ex Post Facto issue “hasn’t been — it hasn’t been raised.” Tr. at 21. This makes no sense. The fact that the sentencing court and counsel for the Government pontificated about the issue at the sentencing hearing on March 1 — while defense counsel remained silent — does not change the legal status of this issue.
The majority’s attempt to reconstruct the facts of this case so as to appear that defense counsel consciously waived an objection on ex post facto grounds is clearly erroneous. Harrison did not waive his rights intentionally. Although, on the first day of sentencing, the district judge was hinting at the potential ex post facto issue, defense counsel was clearly unaware of the implications of the judge’s questions. At most, this is inadvertent forfeiture, not waiver.
The majority’s strongest evidence of waiver boils down to two statements, both of which require a gigantic interpretive leap to conclude that either demonstrates *812an intentional relinquishment of Harrison’s ex post facto right. First, during the first day of the sentencing hearing (February 24), and before the judge ever mentioned the words “ex post facto or the 2002 Guidelines,” the judge asked the attorneys how much discretion he had to depart downward. Defense counsel requested a one-level downward departure in criminal history. Without any mention of the differently worded 2002 Guidelines, defense counsel assumed that the judge’s request was made pursuant to the (more limiting) 2003 version of the Guidelines. This is not evidence of an intentional waiver — it is evidence of an inadvertent forfeiture.
Second, the majority points to February '26 when defense counsel filed an amended motion for downward departure reiterating the request made at the first hearing. Again, at this point, no one mentioned the 2002 Guidelines or the Ex Post Facto Clause. Defense counsel obviously repeated the request because he thought the judge needed clarification on the departure allowed under the 2003 version. Counsel did not comprehend what the judge was getting at, and that is inadvertent forfeiture, not intentional relinquishment.8
Conspicuously lacking from the majority opinion is any express statement in the record made by Harrison or his counsel— at a point in time after the district court mentioned the Ex Post Facto Clause explicitly — 'that he relinquished or waived his right under the Ex Post Facto Clause. It is not surprising that the record should be devoid of such a statement; a fair reading of the record reveals that defense counsel remained mute because he simply did not comprehend what was going on at the hearing. Defense counsel’s confused silence cannot be transformed into an express or intended statement that the Ex Post Facto Clause was inapplicable.9
Once the sentencing resumed on March 1, the judge finally mentioned the Ex Post Facto Clause by name. The Government began to offer an argument to the court on that issue, but the judge explained clearly that the issue was not before the court. As this exchange transpired between the judge and prosecutor, defense counsel remained silent. After the ex post facto issue became explicit, defense counsel never again specified the precise extent of the departure being sought.
It is a stretch to rule that waiver of the Ex Post Facto Clauses’ guarantee can occur where that issue was definitively “not raised” before the court, as the record *813states. But it defies reason to engage in a double-charade and further hold, as the majority does, that such waiver can be achieved by defense counsel’s failure to grasp an issue at which a judge is graciously hinting.
Ex post facto arguments simply were not asserted or waived by Harrison’s counsel, and an inadvertent failure to assert a substantial constitutional right impacting the fairness and integrity of the penal system is precisely what Fed. R.Crim. Proc. 52(b) enables a defendant to resurrect on appeal. Olano, 507 U.S. at 731-32, 113 S.Ct. 1770.
B. Plain Error Affecting Substantial Rights
In the present case, it cannot be disputed that the district court committed plain error that affected a substantial constitutional guarantee contained in the Ex Post Facto Clause — i.e., the unequivocal command that the Government shall not dole out punishment that imposes a harsher sentence than the one permitted by law at the time the crime was committed. See U.S. Const. Art. I, § 9, cl.3; Frank, 354 F.3d at 926.10
If one compares the sentence Harrison received under the 2003 version of the Guidelines with the sentence he likely would have received under the 2002 version, it appears that he would have received a lesser sentence under the earlier version. It is undisputed that the policy statement contained in U.S.S.G. § 4A1.3 (2003) limits the downward departures for career offenders to one criminal history category. Given Harrison’s total offense level of 31 and a criminal history category of V (after application of a single downward departure), the resulting sentencing range was 168-210 months (14-17.5 years).
Even the Government concedes that “[pjrior to November 5, 2003, no such restriction existed allowing the Court to depart horizontally (criminal history category) and vertically (offense level) from the applicable career offender guideline range.” Government’s Brief at 8-9 (citing Greger, 339 F.3d at 668 (8th Cir.2003)). Although the district court did not state definitively what sentence it would have issued to Harrison had it been able to exercise greater discretion, the record reveals that the district court wanted to drop Harrison’s offense level to 23, but leave his criminal history category at VI, which would have produced a sentencing range of 92-115 months (roughly 7.6-9.5 years).11
In light of this analysis, it is clear that the application of the 2003 Guideline imposed a harsher sentence than the prior version. Harrison will serve roughly five to ten additional years than he would have served under the prior sentencing scheme. Moreover, this error encroaches upon a fundamental liberty interest protected by *814the Ex Post Facto Clause. “The presumption against the retroactive application -of new laws is an essential thread in the mantle of protection that the law affords the individual citizen.” Lynce v. Mathis, 519 U.S. 433, 439, 117 S.Ct. 891, 137 L.Ed.2d 63 (1997). In both a temporal and .substantive sense, this error affects “substantial rights.”12
Since the district court applied the 2003 version of the Guidelines and imposed a harsher sentence than if would have under the prior version, U.S.S.G. §' 1B1.11 was violated. This type of deviation from a Guideline binding upon courts is “plain error” within the meaning of Rule 52(b). “If a legal rule was violated during the district court proceedings, and if the defendant did not waive the rule, then there has been an ‘error’ within the meaning of Rule 52(b) despite the absence of a timely objection.” Olano, 507 U.S. at 733-34, 113 S.Ct. 1770.
In short, the district court committed plain error affecting substantial rights, and Harrison did not waive appeal of this error. This case cries out for reversal.
. United States v. Wilson, 184 F.3d 798, 800-01 (8th Cir.1999), appears to state the contrary. I am not confident that Wilson rests on sound reasoning. Wilson states correctly that even a constitutionally guaranteed "procedural” right to appeal may be waived by a criminal defendant. Id. at 800. Yet, the Wilson court refused to consider Wilson’s substantive ex post facto argument on appeal, citing the general rule that a defendant who explicitly and voluntarily exposes himself or herself to a sentence may not challenge that punishment on appeal. Id. at 801. The majority makes an identical mistake. See supra majority opinion at 4-5 (citing United States v. Thompson, 289 F.3d 524, 527 (8th Cir.2002); Wilson, 184 F.3d at 800-01; and United States v. Nguyen, 46 F.3d 781, 783 (8th Cir.1995)). This general rule has no bearing on, and cannot trump, the special review procedure articulated in Fed.R.Crim.P. 52(b). Second, while the generic, procedural right to appeal can be waived, the substantive right prohibiting ex post facto laws cannot. As Michelsen states, the right to appeal a sentence on grounds of illegality survives a knowing and voluntary waiver of appellate rights. See 141 F.3d at 872. To the extent that Wilson and Michelsen create a conflict within our own circuit, this issue warrants further appeal or rehearing.
At any rate, Wilson is factually distinct from the instant case. In Wilson, the defendant's attorney stated at the sentencing hearing that he or she had reviewed the Presentence Investigation Report (PSIR) and "believed it [was] correct and accurate in all matters.” 184 F.3d at 799-800. Here, Harrison's attorney made no such concession at the sentencing hearings. Indeed, ever since the PSIR in this case was released, Harrison and his attorney have argued that the PSIR's recommendation *811of "career offender" status seriously overrepresented Harrison's criminal history. Moreover, Harrison’s plea agreement does not contain a provision stating that he waived his appellate rights.
. Because courts are required to approve plea agreements, the obligation to ensure that plea agreements do not violate the Ex Post Facto Clause probably rests with the court, and may be the type of constitutional issue that any court should be allowed to raise sua sponte.
. See infra Part II.B. at 7-9 (conducting a harshness analysis).
. If not taken out of context, the record shows that defense counsel lodged conflicting and vague requests regarding the extent of departure and relied upon case law that specifically endorsed the sentencing judge's authority to depart downward more than one offense level. See e.g., Def. Brief in Support of Motion for Downward Departure at 6 (requesting that the court "reduce his sentence as justice and fairness dictate” but requesting no specific offense level); Def. Am. Motion for Downward Departure and Request for Oral Argument at 2 (submitted on February 26, and requesting a departure of "one category level from category VI to category V”); Tr. at 13 (basing the departure request on the United States v. Greger, 339 F.3d 666, 668, 671 (8th Cir.2003) — which explicitly allows a sentencing judge to depart both vertically and horizontally — yet also requesting only a single criminal history category departure because the ex post facto issue is not yet clear); Tr. at 24 (asking the court on March 1 to impose a sentence at the low end of the guideline range, but omitting a specification of the applicable range).
. Contrary to the Government's patently incorrect claim in its brief, the transcript from the sentencing hearing contains no concession by defense counsel that, in fact, the new 2003 guideline controlled the extent of departure in this case. Defense counsel merely conceded that the 2003 Guideline amendment "came about in November of 2003.” Tr. at 20.
. Normally, a district court’s decision to deny a downward departure is not reviewable. An exception to this rule is when "the district judge mistakenly believed that he or she lacked the authority to make such a departure,” which is the case here. Frank, 354 F.3d at 926; see also Tr. at 23 (reflecting the judge's statement that he departed downward to the degree authorized under the current law).
. See Tr. at 8 (reflecting the judge’s belief that if the district court opted to grant Harrison’s request for downward departure on the ground that his "career offender” status overrepresented the severity of his criminal history, the court could sentence within the guideline range that would have applied absent the career offender status in its entirety — i.e., the base offense level minus any adjustments); see also United States v. Senior, 935 F.2d 149, 151 (8th Cir.1991) (affirming sentence based on the guideline range that would have applied absent the career offender status).
. .The Government argues that the 2003 amendment to U.S.S.G. § 4A1.3 did not tech- . nically increase the penalty for the crime and therefore did not increase the harshness of Harrison’s sentence. Rather, the Government reasons, the amendment merely restricted the sentencing court's discretionary authority to depart more than one criminal history level. This argument is disingenuous. When a judge’s discretion to grant downward departures is restricted, 'the harshness of a sentence necessarily increases. -The Supreme Court has already rejected the argument that downward departures or other types of penalty credits bear no relation to the severity of a , sentence because they are "not ‘in some technical sense part of the sentence.’ ” Lynce, 519 U.S. at 445-47, 117 S.Ct. 891.
[RJetroactive alteration of parole or early release provisions, like the retroactive application of provisions that govern initial sentencing, implicates the Ex Post Facto Clause because such credits are one determinant of petitioner's prison term ... and ... [the petitioner’s] effective sentence is altered once this determinant is changed.... [T]he removal of such provisions can constitute an increase in punishment, because a prisoner’s eligibility for reduced imprisonment is a significant factor entering into both the defendant’s decision to plea bargain and the judge's calculation of the sentence to be imposed.
Id. at 445-46, 117 S.Ct. 891 (emphasis added and internal citations omitted); see also Weaver v. Graham, 450 U.S. 24, 33-34, 101 S.Ct. 960, 67 L.Ed.2d 17 (1981), overruled on other grounds, Cal. Dep’t Corr. v. Morales, 514 U.S. 499, 506 n. 3, 115 S.Ct. 1597, 131 L.Ed.2d 588 (1995) (holding that a revised Florida statute, which reduced the availability of monthly "gain-time” credits that could operate to reduce a sentence, was retroactively and unconstitutionally applied to defendant in violation of the Ex Post Facto Clause). Thus, it is well-settled that, even though a downward departure under § 4A1.3 is a product of judicial discretion to which a defendant is not necessarily entitled, this does not bar the ex post facto claim. In light of Lynce and Weaver, the Government’s attempt to recycle this argument is ill-taken.