Reversed in part, dismissed in part, and remanded by published opinion. Chief Judge WILKINS wrote the majority opinion, in which Judge ANDERSON joined. Judge GREGORY wrote an opinion concurring in part and dissenting in part.
OPINION
WILKINS, Chief Judge.
The United States appeals an order of the district court dismissing the indictment against Farhad Talebnejad and his parents (collectively, “the Talebnejads”). The Ta-lebnejads were charged with conducting an unlicensed money transmitting business, see 18 U.S.C.A. § 1960 (West Supp.2006). The district court dismissed the indictment on the basis that its allegations were insufficient in numerous respects. See United States v. Talebnejad, 342 F.Supp.2d 346, 353-61 (D.Md.2004). The court declined to address the Talebnejads’ Eighth Amendment challenge to the forfeiture allegations of the indictment on the basis that the claim was premature. See id. at 361. For the reasons set forth below, we reverse the dismissal of the indictment and dismiss the Talebnejads’ cross-appeal of the refusal to consider the Eighth Amendment claim.
I.
A. Relevant Provisions
1. 18 U.S.C.A. § 1960
A money transmitting business is one that, for a fee, accepts currency for transfer within or outside the United States through foreign currency exchanges and financial institutions. See 18 U.S.C.A. § 1960(b)(2); United States v. Velastegui, 199 F.3d 590, 592 (2d Cir.1999). Many of these businesses are operated informally, by immigrants for fellow immigrants from their home countries. In 1992, Congress sought “to combat the growing use of money transmitting businesses to transfer large amounts of the monetary proceeds of unlawful enterprises” by enacting § 1960. Velastegui, 199 F.3d at 593. Prior to 2001, the statute provided, in pertinent part:
(a) Whoever conducts, controls, manages, supervises, directs, or owns all or part of a business, knowing the business is an illegal money transmitting business, shall be fined in accordance with this title or imprisoned not more than 5 years, or both.
(b) As used in this section—
(1) the term “illegal money transmitting business” means a money transmitting business which affects interstate or foreign commerce in any manner or degree and—
(A) is intentionally operated without an appropriate money transmitting license in a State where such [566]*566operation is punishable as a misdemeanor or a felony under State law; or
(B) fails to comply with the money transmitting business registration requirements under section 5330 of title 31, United States Code, or regulations prescribed under such section....
18 U.S.C.A. § 1960, historical & statutory notes (West Supp.2006) (emphasis added) (internal quotation marks omitted).
On October 26, 2001, Congress amended the statute to provide, in relevant part, as follows:
(a) Whoever knowingly conducts, controls, manages, supervises, directs, or owns all or part of an unlicensed money transmitting business, shall be fined in accordance with this title or imprisoned not more than 5 years, or both.
(b) As used in this section—
(1) the term “unlicensed money transmitting business” means a money transmitting business which affects interstate or foreign commerce in any manner or degree and—
(A) is operated without an appropriate money transmitting license in a State where such operation is punishable as a misdemeanor or a felony under State law, tvhether or not the defendant knew that the operation was required to be licensed or that the operation was so punishable; [or]
(B) fails to comply with the money transmitting business registration requirements under section 5330 of title 31, United States Code, or regulations prescribed under such section....
18 U.S.C.A. § 1960 (emphasis added). The purpose of the amendment was to eliminate a potentially available affirmative defense that the defendant was unaware of applicable state licensing requirements. See H.R.Rep. No. 107-250, pt. I, at 54 (2001) (explaining that the amendment “clarifies the scienter requirement in § 1960 to avoid the problems that occurred when the Supreme Court interpreted the currency transaction reporting statutes to require proof that the defendant knew that structuring a cash transaction to avoid the reporting requirements had been made a criminal offense. See Ratzlaf v. United States, [510 U.S. 135,] 114 S.Ct. 655 [126 L.Ed.2d 615] (1994). The proposal makes clear that an offense under § 1960 is a general intent crime for which a defendant is liable if he knowingly operates an unlicensed money transmitting business.”).
2. Maryland Law
Maryland law prohibits a person from engaging in “the business of money transmission” unless that person is a licensee, is a delegate of a licensee, or is exempt from the licensing requirement. Md.Code Ann., Fin. Inst. § 12-05 (LexisNexis 2003). “Money transmission” is defined as “the business of selling or issuing payment instruments or stored value devices, or receiving money or monetary value, for transmission to a location within or outside the United States” and includes “[a]ny informal money transfer system engaged in as a business for ... facilitating the transfer of money outside the conventional financial institutions system to a location within or outside the United States.” Md. Code Ann., Fin. Inst. § 12-401(l) (Lexis-Nexis 2003). Maryland law sets forth criminal penalties for “[a]ny person who knowingly and willfully violates” the licensing requirement. Md.Code Ann., Fin. Inst. § 12-130 (LexisNexis 2003) (emphasis added).
3. Federal Regulations
Although § 1960 has made failure to comply with federal registration requirements punishable since 1994, see 18 U.S.C.A. § 1960, historical & statutory notes (West 2000), pertinent regulations were not promulgated until 1999 and did not become effective until December 31, [567]*5672001. The actual content of applicable federal regulations is not pertinent to the issues before us.
B. The Talebnejads
The Talebnejads are Iranian immigrants. Farhad Talebnejad operated two money transmitting businesses — Shirazi Money Exchange, Inc., and Shirazi Arz, Inc. — out of his parents’ home in Rockville, Maryland. The businesses were not licensed under Maryland law, nor were they registered pursuant to 31 U.S.C.A. § 5330 (West 2003). In late 1995, Talebnejad investigated the possibility of obtaining licenses, but decided not to do so because he could not afford the cost and he believed that the licensing statute did not apply to his businesses.
In November 2003, the Talebnejads were charged with one count of conspiring to conduct an unlicensed money transmitting business and with two substantive counts of conducting an unlicensed money transmitting business.1 All three counts alleged that the businesses were “unlicensed” within the meaning of § 1960(a) because (1) the businesses were required to be licensed under Maryland law, and were not, in violation of § 1960(b)(1)(A); and (2) the businesses were required to be registered with the federal government, and were not, in violation of § 1960(b)(1)(B).2 The indictment also sought forfeiture of approximately $18 million in property traceable to the charged offenses.
The Talebnejads moved to dismiss the indictment, asserting that (1) § 1960(b)(1)(A) violated the Equal Protection Clause because not all states require money transmitting businesses to be licensed; (2) § 1960(b)(1)(A) violated the Due Process Clause because it lacked a scienter requirement as to the applicability of state licensing laws; (3) § 1960(b)(1)(A) was unconstitutionally vague in several respects; and (4) the indictment failed to adequately inform the Talebnejads of the offenses charged.
The district court granted the motion.3 With respect to the due process challenge to the lack of a scienter requirement in § 1960(b)(1)(A), the court recognized that “Congress attempted to exclude any mens rea requirement when it amended § (b)(1)(A).” Talebnejad, 342 F.Supp.2d at 353. But, the court observed, § 1960(b)(1)(A) “still refers to the operation of such a business where such operation is punishable as a misdemeanor or felony under State law.” Id. (internal quotation marks omitted). The court concluded that “the plain meaning of these words is that unless the lack of a license is ‘punishable’ under state law, it is not a federal crime at all,” and that the Government therefore was required to allege and prove an actual violation of state law in order to prove a violation of § 1960. Id. at 354-55. Because the indictment did not allege that Talebnejad had “knowingly and willfully” failed to obtain a license, Md.Code Ann., Fin. Inst. § 12-430, the court ruled it was deficient, see Talebnejad, 342 F.Supp.2d at 355. The district court acknowledged the potential conflict between its analysis of [568]*568the statute and the expressed intent of Congress to omit any scienter requirement with respect, to state licensing obligations, but purported to avoid this conflict by declaring that portion of § 1960 “merely inoperative” in states that have identified a mens rea for violation of licensing requirements. Id.
Although the Talebnejads did not challenge the constitutionality of § 1960(b)(1)(B), the district court nevertheless considered that provision as well. See id. at 355-56. Noting that Congress had not “clearly expressed” its intent to exclude a mens rea from a violation of § 1960(b)(1)(B), the court ruled that the Government could obtain a conviction under that provision only by “alleg[ing] and prov[ing] that the Defendant acted knowing that he had an obligation to register and that he willfully failed to do so.” Id. at 356.
II.
We first consider the Talebnejads’ claims regarding the § 1960(b)(1)(A) charge.
A. Due Process Challenge
As noted above, § 1960(b)(1)(A) provides that it is a federal offense to (1) operate a money transmitting business, (2) that affects interstate commerce, and (3) that is unlicensed under state law, when (4) state law requires a license and (5) state law punishes lack of a license as a felony or misdemeanor. See 18 U.S.C.A. § 1960(b)(1)(A). The parties agree that the Government must allege and prove the defendant’s knowledge with respect to the first three elements and that Congress explicitly excluded any mens rea requirement from the last two elements. The question, therefore, is whether the statute is constitutional in the absence of a mens rea requirement as to these two elements.
The definition of federal criminal offenses lies within the province of Congress. See Liparota v. United States, 471 U.S. 419, 424, 105 S.Ct. 2084, 85 L.Ed.2d 434 (1985). There is no question that, at least under some circumstances, Congress may dispense with a mens rea element, see Staples v. United States, 511 U.S. 600, 606, 114 S.Ct. 1793, 128 L.Ed.2d 608 (1994), as it has clearly done with respect to § 1960(b)(1)(A). The clear language of § 1960(b)(1)(A) requires us to reject the attempt of the district court to avoid the constitutional question through statutory construction, i.e., by incorporating the Maryland intent requirement into the federal statute and declaring Congress’ language regarding intent to be surplusage. See Talebnejad, 342 F.Supp.2d at 353—55; see also Md.Code Ann., Fin. Inst. § 12-430 (setting forth criminal penalties for “knowingly and willfully violat[ing]” the licensing requirement). First, the principle that a statute should be construed so as to avoid a grave constitutional question — as the district court evidently sought to do — “has no application” when, as here, the statute is unambiguous. United States v. Oakland Cannabis Buyers’ Coop., 532 U.S. 483, 494, 121 S.Ct. 1711, 149 L.Ed.2d 722 (2001). Second, “[a] well-recognized canon of construction requires courts to read statutory provisions so that, when possible, no part of the statute is superfluous.” United States v. Childress, 104 F.3d 47, 52 (4th Cir.1996). In light of these principles, the district court was obliged to give effect to Congress’ clearly expressed intent that no mens rea — whether derived from § 1960 itself or from an underlying state statute— was to attach to the latter two elements of a § 1960(b)(1)(A) offense.4
[569]*569The essence of the Talebnejads’ due process challenge to § 1960(b)(1)(A) is that Congress exceeded constitutional bounds when it declared that ignorance of state licensing requirements is not a defense to liability under the federal statute. For the reasons set forth below, however, we agree with the Government that § 1960(b)(1)(A) passes constitutional muster because it “requires ... defendants to know the facts that make their conduct illegal,” Appellant’s Br. at 27, and omits a knowledge requirement only as to legal obligations.
The Supreme Court has indicated that there are limits to the authority of Congress to omit a mens rea requirement as to one or more elements of an offense. For example, in United States v. X-Citement Video, Inc., 513 U.S. 64, 115 S.Ct. 464, 130 L.Ed.2d 372 (1994), the Court considered the proper construction of a federal statute prohibiting the knowing interstate transportation of a visual depiction of a minor engaged in sexually explicit conduct. See X-Citement Video, 513 U.S. at 65-66, 115 S.Ct. 464. The Supreme Court rejected the Government’s argument that the defendant could be convicted without knowing that the person depicted was a minor, reasoning in part that such a reading of the statute was constitutionally problematic because the presence of a minor in the video made the difference between conduct that was constitutionally protected (possession of pornography) and conduct that was not (possession of obscenity). See id. at 72-73, 78, 115 S.Ct. 464. Similarly, Staples involved the question of whether a statute that prohibited receipt or possession of an unregistered firearm should be construed so as to include a mens rea with respect to the facts that brought a particular weapon within the limited, statutory definition of “firearm.” See Staples, 511 U.S. at 603-04, 114 S.Ct. 1793. Citing the “long tradition of widespread lawful gun ownership by private individuals in this country,” id. at 610, 114 S.Ct. 1793, the Court concluded that an individual could be convicted under the statute only if the factfinder determined that the defendant knew of the factual characteristics that brought the weapon within the statutory definition, see id. at 619, 114 S.Ct. 1793.
Justice Ginsburg, concurring in the judgment in Staples, was careful to note that the presumption that a mens rea attaches to the elements of the offense “requires knowledge only of the facts that make the defendant’s conduct illegal, lest it conflict with the related presumption, deeply rooted in the American legal system, that, ordinarily, ignorance of the law or a mistake of law is no defense to criminal prosecution.” Staples, 511 U.S. at 622 n. 3, 114 S.Ct. 1793 (Ginsburg, J., concurring in the judgment) (internal quotation marks omitted). It is here that the Taleb-nejads’ challenge to § 1960(b)(1)(A) founders.5 Both X-Citement Video and Staples [570]*570concerned whether due process required the inclusion of a mens rea as to a factual element of a crime, not a legal element. Accord Bryan v. United States, 524 U.S. 184, 192, 118 S.Ct. 1939, 141 L.Ed.2d 197 (1998) (“[T]he knowledge requisite to knowing violation of a statute is factual knowledge as distinguished from knowledge of the law.” (internal quotation marks omitted)). Here, the Talebnejads claim that due process requires the Government to prove that they knew that their operation of an unlicensed money transmitting business violated state law.
The Supreme Court has recognized a “mistake of law” defense in only one case. In Lambert v. California, 355 U.S. 225, 78 S.Ct. 240, 2 L.Ed.2d 228 (1957), the Supreme Court considered the constitutionality of a municipal ordinance that required a convicted felon to register with the city, and subjected the felon to criminal penalties even if he or she was unaware of the registration requirement, see id. at 226-27, 78 S.Ct. 240. The Court held that the Due Process Clause “places some limits on [the] exercise” of the rule that ignorance of the law is no excuse, and concluded that the ordinance exceeded those limits. Id. at 228, 78 S.Ct. 240. The key to the ruling of the Court was its characterization of the conduct at issue as “wholly passive,” in that violation of the ordinance was “unaccompanied by any activity whatever, mere presence in the city being the test.” Id. at 228-29, 78 S.Ct. 240. The same cannot be said of the licensing requirement of § 1960(b)(1)(A), which reaches the unquestionably active conduct of operating a business.
Liparota, on which the Talebnejads rely, is of no help to them.6 There, the Supreme Court considered the mens rea necessary to convict the defendant of unauthorized acquisition of food stamps. Noting the many innocent circumstances under which an individual might acquire or use food stamps without authorization (for example, by being the recipient of a mistaken mailing), see Liparota, 471 U.S. at 426-27, 105 S.Ct. 2084, the Court held that the Government was required to demonstrate that the defendant knew that his acquisition of the food stamps was unauthorized, see id. at 425, 105 S.Ct. 2084. Liparota does not aid the Talebnejads’ due process challenge because Liparota concerned only a question of statutory construction; once the Supreme Court construed the statute to require knowledge of the lack of authorization for conviction, it had no occasion to consider whether the absence of a knowledge requirement would violate due process.
In summary, we conclude — consistent with an unbroken line of Supreme Court precedent — that § 1960(b)(1)(A) requires a mens rea of knowledge only as to the factual elements of the offense. The Due Process Clause did not require Congress to include a mens rea as to the legal elements of the crime, and we reject the Talebnejads’ argument to the contrary.
B. Other Challenges
The district court also ruled the indictment deficient because it failed to address the effect of an amendment to Maryland law and because it did not allege that the Talebnejads had a duty under Maryland [571]*571law to obtain a license. We address these issues below.
1.
The Maryland money transmitting statute was amended effective October 1, 2002, to make changes to the definition of “money transmission.” Without addressing the materiality of these amendments, the district court concluded that “the pre-October 1, 2002 definitions must be satisfied with respect to pre-October 1, 2002 activities and the post-October 1, 2002 definitions satisfied as to the post October 1, 2002 activities.” Talebnejad, 342 F.Supp.2d at 358.
We agree with the district court that if the amendment of Maryland law broadened the definition of “money transmission”- — -and thus, broadened the applicability of the licensing requirement — prosecuting pre-October 1, 2002 conduct under the post-October 1, 2002 statute would violate the Ex Post Facto Clause. In other words, if business activity “A” was not required to be licensed prior to October 1, 2002 — and thus it was not a violation of federal law to engage in the activity without a state license — it would be a violation of the Ex Post Facto Clause to prosecute that conduct on the basis that it required a license after the October 1, 2002 amendment. See Weaver v. Graham, 450 U.S. 24, 28, 101 S.Ct. 960, 67 L.Ed.2d 17 (1981) (defining an ex post facto law as “any law which imposes a punishment for an act which was not punishable at the time it was committed” (internal quotation marks omitted)).
We conclude, however, that dismissal of the indictment is not required simply because Maryland law was amended during the time frame of the offense that is alleged in the indictment. An indictment meets the requirements of the Fifth and Sixth Amendments “if it, first, contains the elements of the offense charged and fairly informs a defendant of the charge against which he must defend, and, second, enables him to plead an acquittal or conviction in bar of future prosecutions for the same offense.” Hamling v. United States, 418 U.S. 87, 117, 94 S.Ct. 2887, 41 L.Ed.2d 590 (1974). “Where a particular date is not a substantive element of the crime charged, strict chronological specificity or accuracy is not required.” United States v. Kimberlin, 18 F.3d 1156, 1159 (4th Cir.1994) (internal quotation marks omitted). Here, the indictment alleges that the Talebnejads operated an unlicensed money transmitting business, in violation of § 1960(b)(1)(A), “[bjeginning no earlier than October 26, 2001 and continuing to in or about December 2002.” J.A. 25. The offense is proved if, at any time during the period alleged by the indictment, the Talebnejads’ business was subject to the Maryland licensing requirement.7 Although the case may be made more difficult (for both parties) by the necessity of addressing two versions of the state licensing requirement, the burden on the Talebnejads is not so great as to amount to a violation of due process.8
[572]*5722.
The district court also concluded that the indictment was defective because it did not allege that the Talebnejads had a duty to acquire a license under Maryland law. See Talebnejad, 342 F.Supp.2d at 359. The court reasoned that unless the Government was required to allege and prove a duty to obtain a license, “any number of individuals affiliated with an unlicensed money transmitting business could be punished under § 1960.” Id. This simply is not an accurate reading of the statute. Section 1960(b)(1)(A) applies only to one who “conducts, controls, manages, supervises, directs, or owns” a money transmitting business, knowing that it is not licensed, 18 U.S.C.A. § 1960(a). Criminal liability is thus clearly directed toward those who are, in some substantial degree, in charge of the operation; the statute does not reach mere employees. We therefore reject the conclusion of the district court that the Government is required to allege and prove a state-law duty to acquire a license in order to obtain a conviction under § 1960(b)(1)(A).
hi.
The district court also concluded that the indictment was lacking with respect to the charge that the Talebnejads violated § 1960(b)(1)(B), which defines an “unlicensed money transmitting business” as one that “fails to comply with the money transmitting business registration requirements” of 31 U.S.C.A. § 5330 and related regulations. With respect to this provision, the district court concluded that the Government was required “to allege and prove that the Defendant acted knowing that he had an obligation to register and that he wilfully failed to do so.” Ta-lebnejad, 342 F.Supp.2d at 356. It based this conclusion on “Congress’s failure to amend ... § (b)(1)(B) when it amended § (b)(1)(A)” and on “[t]he conventional understanding ... that mens rea is a fundamental component of every criminal act.” Id.
We cannot accept the reasoning of the district court. Section 1960, as currently written, applies to whoever “knowingly conducts ... an unlicensed money transmitting business,” 18 U.S.C.A. § 1960(a), and defines “unlicensed money transmitting business,” in relevant part, as “a money transmitting business which affects interstate or foreign commerce ... and ... fails to comply with the money transmitting business registration requirements” set forth in 31 U.S.C.A. § 5330 or accompanying regulations, 18 U.S.C.A. § 1960(b)(1)(B). There is no question here that the Government must prove the Ta-lebnejads’ knowledge as to all of the factual elements of the crime: that they were conducting a money transmitting business that affected interstate commerce and that was unregistered. Therefore, § 1960(b)(1)(B) sets forth a constitutionally valid general intent crime, just as § 1960(b)(1)(A) does. See Bryan, 524 U.S. at 192, 118 S.Ct. 1939. Nothing in the statutory language — such as the use of the word “willful” — suggests that the Government must additionally prove knowledge of the law. Further, it is not relevant that Congress made no change to § 1960(b)(1)(B) when it amended § 1960(b)(1)(A); there has never been a question as to whether a conviction under § 1960(b)(1)(B) required proof of the defendant’s knowledge of the law.9 See [573]*573United States v. Uddin, 365 F.Supp.2d 825, 829 (E.D.Mich.2005).
IV.
The Talebnejads cross-appeal the portion of the district court order that declined to address their challenge to the forfeiture allegations of the indictment. The Talebnejads maintain that the $18 million forfeiture sought by the Government violates the Excessive Fines Clause of the Eighth Amendment. We agree with the district court that this challenge is not yet ripe. Accord United States v. Covey, 232 F.3d 641, 646 (8th Cir.2000) (‘We do not have jurisdiction [over an appeal of a preliminary forfeiture order] when no final forfeiture order or judgment has been entered. .. .”). Accordingly, we dismiss the Talebnejads’ cross-appeal.
V.
For the reasons set forth above, we reverse the dismissal of the indictment and remand for further proceedings. The Ta-lebnejads’ cross-appeal is dismissed.
REVERSED IN PART, DISMISSED IN PART, AND REMANDED.