The appellant, William J. Kirk, entered a conditional guilty plea in the district court to one count of unlawful possession of a ma-chinegun under 18 U.S.C. § 922(g).1 On appeal, Kirk challenges the indictment and the district court’s sentence calculation. Finding no error, we affirm.
I. FACTS
On September 1, 1988, Kirk offered to sell a machinegun to Donald Mueller. From September 1988 through January 4, 1989, Kirk attempted to sell various unregistered machineguns to Mueller. On January 4, 1989, Kirk agreed to sell Mueller an M-16 machinegun for $1,200.00. Mueller then went with Kirk to a rifle range in Dripping Springs, Texas where they obtained certain parts necessary for a machinegun conversion. Kirk used the parts to convert a semi-automatic EA Company Rifle, .223 caliber, model J-15, to a machinegun. Kirk and Mueller test-fired the converted machinegun with blank ammunition, and the transaction was completed.
On February 12,1989, Kirk made arrangements with Mueller to sell him an UZI ma-chinegun for $1,100.00 in cash plus a $900.00 commercial welder. On February 21, 1989, at the same rifle range, the cash and welder were exchanged for an Action Arms Limited UZI carbine, Model A, 9 millimeter bearing serial number SA32084, which had been converted to a machinegun by the addition of an UZI machine bolt. Mueller test-fired the UZI in the fully automatic mode. John M. Clark accompanied Mueller on February 21 and witnessed the transaction. Apparently, through Mueller’s cooperation, a number of the meetings and conversations between Kirk and Mueller were monitored by the Bureau of Alcohol, Tobacco and Firearms.
Kirk was arrested November 28,1989. He was charged with firearms violations in eight counts of a ten-count superseding indictment. On the day trial was scheduled, Kirk pled guilty to one count, charging unlawful pos*793session of an unregistered firearm in violation of 26 U.S.C. § 5861(d). Kirk appealed his conviction, arguing that section 5861 had been implicitly repealed by the passage of 18 U.S.C. § 922(o). Based on authority from other circuits supporting Kirk’s argument, the parties jointly moved to remand the case to the district court for dismissal of the conviction under Rule 48(a) of the Federal Rules of Criminal Procedure.2
After the first conviction was set aside, Kirk was charged on December 21,1993 in a four-count indictment with violations of 18 U.S.C. § 922(o): unlawful possession of a machinegun on January 4, 1989 (Count One); unlawful transfer of a machinegun on January 4,1989 (Count Two); unlawful possession of a machinegun on February 21, 1989 (Count Three); and unlawful transfer of a machinegun on February 21, 1989 (Count Four). Kirk filed a motion to dismiss the indictment, arguing that section 922(o) was unconstitutional because it exceeded the power of the federal government under the Commerce Clause and because the indictment failed to allege a connection with interstate commerce. Kirk also challenged his prosecution on the basis of the plea agreement entered in the first prosecution and on the basis of double jeopardy. The district court overruled these contentions. Kirk entered a conditional guilty plea to count one of the indictment, preserving the right to appeal the district court’s rulings.
Kirk was sentenced on June 24, 1994. In calculating Kirk’s sentencing range under the sentencing guidelines, the district court increased the defendant’s offense level for obstruction of justice. The district court sentenced Kirk to a term of imprisonment of twelve months and one day, a term of supervised release of three years, a fine of $3,000.00 and a special assessment. The defendant timely filed this appeal.
II. DISCUSSION
A.
Kirk first contends that the district court erred in denying his motion for specific performance of his prior plea agreement. Kirk claims that as part of the first plea agreement in 1991, the government promised that if Kirk were successful on appeal, it would not bring a subsequent prosecution based on the same conduct. Thus, Kirk argues, the subsequent prosecution was barred by that prior agreement.
If a plea agreement exists, and a plea of guilty has been in some way induced by a promise, it is essential to the fairness of the proceeding that the promise be fulfilled. Santobello v. New York, 404 U.S. 257, 262, 92 S.Ct. 495, 499, 30 L.Ed.2d 427 (1971). This circuit requires the government to strictly comply with the agreements it makes with defendants. United States v. Chagra, 957 F.2d 192, 194 (5th Cir.1992). A court’s inquiry regarding whether a particular promise induced a guilty plea does not necessarily end with a reading of the written agreement. Evidence of discussions surrounding the negotiations of the written agreement may establish the existence of a promise. United States v. Williams, 809 F.2d 1072, 1079 (5th Cir.1987), cert. denied, 484 U.S. 896, 108 S.Ct. 228, 98 L.Ed.2d 187 (1987). We will reverse a district court’s findings in this regard only if clearly erroneous. Id.
At a hearing in the district court, Kirk testified that at the time he was deciding to plead guilty in 1991, the assistant U.S. attorney told him that he could appeal his conviction based on the constitutionality of the statute, and that if he was successful the government would not bother him any more. However, the AUSA, Gerald Carruth, testified that there was no agreement not to pursue other charges if the conviction did not stand up. In fact, Carruth testified that at no time did the government agree to “give up” if Kirk’s appeal was successful.
The written plea agreement presented in January 1991 contained only the agreement to dismiss the other charges at sentencing and the standard language regarding the government’s right to proceed with prosecu*794tion should the defendant withdraw his guilty plea prior to sentencing. The written agreement contained no promise not to re-prosecute in the event Kirk’s appeal was successful. The record on appeal also reveals that at the plea hearing held January 23, 1991, after the plea agreement was presented to the district court, the court inquired “Has anyone made any promise to you other than the plea agreement that induced you to plead guilty?” The defendant responded “No, sir.”
The district court found, based on the evidence presented, that the defendant entered into the first plea agreement because of the strength of the evidence against him, including recorded conversations, and not because of any promise not to prosecute in case of a successful appeal. In addition, the district court found that the defendant had not established by a preponderance of the evidence that AUSA Carruth made the alleged promise. This finding was based on the testimony of the defendant and the attorneys involved and necessarily depended on an evaluation of credibility by the district court.
“It is not this Court’s function to pass on a district court’s determination regarding the credibility of witnesses.” United States v. Alaniz-Alaniz, 38 F.3d 788, 791 (5th Cir.1994), cert. denied, — U.S. -, 115 S.Ct. 1412, 131 L.Ed.2d 297 (1995). Given the testimony of the parties, there were two permissible views of the evidence. The district court chose one view based on its ability to weigh the evidence and evaluate the credibility of the witnesses. Under these circumstances, we cannot hold that the district court’s findings are clearly erroneous.
B.
The appellant next argues that his prosecution under section 922(o) violated his rights under the Double Jeopardy Clause of the Fifth Amendment because he had been placed in jeopardy for the same conduct in the previous prosecution under 26 U.S.C. § 5861(d). As noted above, the instant prosecution under section 922(o) was not commenced until after the prosecution under 26 U.S.C. § 5861(d) was dismissed because of a perceived infirmity.3
The Double Jeopardy Clause provides that no person shall “be twice put in jeopardy of life or limb” for the “same offence.” U.S. Const, amend. V.
It has long been settled, however, that the Double Jeopardy Clause’s general prohibition against successive prosecutions does not prevent the government from retrying a defendant who succeeds in getting his first conviction set aside, through direct appeal or collateral attack, because of some error in the proceedings leading to the conviction.
Lockhart v. Nelson, 488 U.S. 33, 38, 109 S.Ct. 285, 102 L.Ed.2d 265 (1988). The exception to this rule, not applicable in this case, is that if the defendant succeeds in having his first conviction set aside on the ground that the evidence presented was insufficient, a re-prosecution is barred because the defendant was entitled to an acquittal at the first trial. Lockhart, 488 U.S. at 39, 109 S.Ct. at 290; Burks v. United States, 437 U.S. 1, 98 S.Ct. 2141, 57 L.Ed.2d 1 (1978).
The first prosecution in the present case was set aside not by a court’s determination that there was error, but by agreement of the parties that, according to persuasive authority, the statute under which Kirk was convicted had been implicitly repealed. This is the type of trial error to which the general rule of Lockhart applies. It makes no difference that this Court’s review of the first conviction was preempted by motion of the government under Rule 48 of the Federal Rules of Criminal Procedure. Thus, the prosecution of Kirk under 18 U.S.C. § 922(o), after a prosecution dismissed for a perceived “defect in the charging instrument,” does not offend the Double Jeopardy Clause. See *795Montana v. Hall, 481 U.S. 400, 403, 107 S.Ct. 1825, 1827, 95 L.Ed.2d 354 (1987).4
C.
Kirk also challenges his conviction on the ground that 18 U.S.C. § 922(o) is unconstitutional. Section 922(o) provides, in relevant part,
(o)(l) Except as provided in paragraph (2), it shall be unlawful for any person to transfer or possess a machinegun.
(2) This subsection does not apply with respect to—
s};
(B) any lawful transfer or lawful possession of a machinegun that was lawfully possessed before the date this subsection takes effect.
The effective date of this provision was May 19, 1986. Kirk contends that this section is unconstitutional because it is beyond the authority granted to Congress under the Commerce Clause. We must analyze this contention in light of the Supreme Court’s recent pronouncement in United States v. Lopez, — U.S. -, 115 S.Ct. 1624, 131 L.Ed.2d 626 (1995).5
In Lopez, the Supreme Court addressed the constitutionality of the Gun Free School Zones Act of 1990, 18 U.S.C. § 922(q). Section 922(q) made it unlawful “for any individual knowingly to possess a firearm at a place that the individual knows, or has reasonable cause to believe, is a school zone.” The Supreme Court affirmed this Court’s ruling that section 922(q) was beyond the scope of the Commerce power, and thus was unconstitutional.
In evaluating section 922(q)’s constitutionality, the Supreme Court described three categories of activity which Congress could regulate under the Commerce Clause:6 (1) the use of the channels of interstate commerce; (2) “the instrumentalities of interstate commerce, or persons or things in interstate commerce, even though the threat may come only from intrastate activities”; and (3) activities which have “a substantial relation to interstate commerce ... i.e., those activities that substantially affect interstate commerce.” Lopez, — U.S. at ---, 115 S.Ct. at 1629-30. The Court held that section 922(q) did not fall within the first two categories because it did not regulate the channels or instrumentalities of interstate commerce. Thus, the Court evaluated section 922(q) under the third category to determine whether it was a regulation of an activity that substantially affected interstate commerce.
The Supreme Court held that section 922(q) “by its terms has nothing to do with ‘commerce’ or any sort of economic enterprise, however broadly one might define those terms.” Id., — U.S. at---, 115 S.Ct. at 1630-31. The Court also held that “possession of a gun in a local school zone is in no sense an economic activity that might, through repetition elsewhere, substantially affect any sort of interstate commerce.” Id., — U.S. at —, 115 S.Ct. at 1634. Thus, the Court found section 922(q) unconstitutional under the Commerce Clause.
Although Lopez is instructive regarding the proper Commerce Clause analysis, it does not control the result in our analysis of section 922(o). We are not the first court to address section 922(o) in light of Lopez. In this regard, we have the benefit of the Tenth Circuit’s opinion in United States v. Wilks, 58 F.3d 1518 (10th Cir.1995). The Wilks court held that “unlike § 922(q), § 922(o) embodies a proper exercise of Congress’ power to regulate ‘things in interstate commerce’ — i.e., machineguns.” Id. at 1521. “The interstate flow of machineguns,” the court said, “‘not only has a substantial effect on interstate *796commerce; it is interstate commerce.’ ” Id. (quoting United States v. Hunter, 843 F.Supp. 235, 249 (E.D.Mich.1994)). We agree.
It is particularly important to our determination that section 922(o) prohibits the private possession or transfer of machineguns only if they were not lawfully possessed prior to May 19, 1986. 18 U.S.C. § 922(o). Thus, transfer or possession of a maehinegun is unlawful under this section only if it was manufactured or illegally transferred after May 19, 1986. It is clear, therefore, that the activity Congress intended to prohibit by application of section 922(o) was the introduction into the stream of commerce machine-guns manufactured, imported, or otherwise illegally obtained, after the effective date of the act. When read as a whole, it is plain that the activities prohibited by section 922(o) constitute commerce.7 We recognized the difference between this regulation and the Gun Free School Zones Act in our opinion in United States v. Lopez, 2 F.3d 1342 (5th Cir.1993):
Section 922(o) is restricted to a narrow class of highly destructive, sophisticated weapons that have been either manufactured or imported after enactment of the Firearms Owners Protection Act, which is more suggestive of a nexus to or affect on interstate or foreign commerce than possession of any firearms whatever, no matter when or where originated, within one thousand feet of the grounds of any school.
2 F.3d at 1356 (emphasis in original; footnote omitted).
Defendant Kirk attempts to avoid section 922(o)’s relation to interstate commerce by characterizing the alleged “crime” in this case as “mere possession” of a maehinegun.8 At the same time, however, Kirk challenges the constitutionality of section 922(o) on its face. In evaluating this type of challenge, we must necessarily consider the scope of section 922(o). As noted above, the “possession” prohibited by section 922(o) is limited to possession of machineguns not lawfully possessed before the effective date of the act. To put it simply, there could be no unlawful possession under section 922(o) without an unlawful transfer. In this context, the limited ban on possession of machineguns must be seen as a necessary and proper measure meant to allow law enforcement to detect illegal transfers where the banned commodity has come to rest: in the receiver’s possession. In effect, the ban on such possession is an attempt to control the interstate market for machineguns by creating criminal liability for those who would constitute the demand-side of the market, i.e., those who would facilitate illegal transfer out of the desire to acquire mere possession.
Thus, section 922(o) falls into the first category identified by the Supreme Court in Lopez: a regulation of the use of the channels of interstate commerce. In other words, section 922(o) is a regulation which attempts “to prohibit the interstate transportation of a *797commodity through the channels of commerce.” — U.S. at -, 115 S.Ct. at 1680. This type of regulation is within the commerce power even though, admittedly, some of the activity made unlawful is purely intrastate. As with federal regulation of controlled substances, see 21 U.S.C. § 801, et seq., there is a rational basis to conclude that federal regulation of intrastate incidents of transfer and possession is essential to effective control of the interstate incidents of such traffic. Therefore, we hold that the prohibition of transfer or possession of post-1986 maehineguns in 18 U.S.C. § 922(o) is a rational exercise of the authority granted Congress under the Commerce Clause.9
D.
Finally, with regard to his sentence, Kirk argues that the district court erred in applying the enhancement for obstruction of justice under section 3C1.1 of the federal sentencing guidelines. That section provides
If the defendant willfully obstructed or impeded, or attempted to obstruct or impede, the administration of justice during the investigation, prosecution, or sentencing of the instant offense, increase the offense level by 2 levels.
United States Sentencing Commission, Guidelines Manual, § 3C1.1 (Nov. 1994).10 Kirk contends that the conduct for which the two level increase was imposed was not related to the “instant offense” as required by this Guideline.
According to the Presentenee Investigation Report, Kirk contacted John M. Clark after a search warrant was executed at Kirk’s place of business but before he was indicted or arrested. Clark was present on February 21, 1989, when Kirk converted an UZI carbine from semi-automatic to fully automatic and test-fired the weapon at the rifle range. Kirk instructed Clark not to cooperate with authorities concerning his knowledge of.these events. The offense to which Kirk pled guilty involved possession of a machinegun on January 4, 1989. Kirk argues that because Clark’s knowledge of Kirk’s activities did not relate specifically to this event, his attempted obstruction did not relate to the offense of conviction, and therefore did not relate to the “instant offense” as required by section 3C1.1.
Kirk cites three decisions from other circuits that support his position. See United States v. Bagwell, 30 F.3d 1454 (11th Cir.1994); United States v. Woods, 24 F.3d 514 (3d Cir.1994); United States v. Perdomo, 927 F.2d 111 (2d Cir.1991). However, after a careful reading of section 3C1.1, we must respectfully disagree with these decisions. Instead, we find the reasoning of the Sixth Circuit persuasive.
In United States v. Crousore, 1 F.3d 382 (6th Cir.1993), the court addressed the same argument Kirk presents in the present ease. In rejecting the defendant’s argument, the court said
This guideline [§ 3C1.1] applies to conduct during the investigation, prosecution, and sentencing of the instant offense, i.e., the offense for which the defendant is being sentenced under the Guidelines.
Whether [the defendant’s] lie was about his guilt on the specific charges to which he pleaded guilty is not an issue under § 3C1.1.
* * * sfi * *
Therefore, the test is not whether the false statement [obstruction] was about the actual crime charged, but whether it was *798made during the investigation, prosecution, or sentencing of the “instant offense.”
1 F.3d at 385. The court also noted that an attempt to conceal trivial or immaterial information would not warrant the obstruction enhancement. “Material information is information that, if believed, would tend to influence or affect the issue under determination.” Id.
We agree with the Sixth Circuit. The enhancement for obstruction of justice under section 3C1.1 is proper anytime the defendant has concealed or attempted to conceal information material to the investigation, prosecution, or sentencing of the instant offense. Although this Guideline clearly contemplates a relationship between the information concealed and the offense conduct, it does not require that it be related directly to a particular offense to which the defendant pleads guilty. To hold otherwise would make the sentencing court’s ability to consider obstructive behavior dependent on the offense in a multiple-count indictment the parties choose to make the subject of a plea bargain.
It is clear in the present case that at the time Kirk solicited Clark’s aid in impeding the government’s investigation, Clark’s personal knowledge of the events on February 21, 1989 were material to the investigation and prosecution of the firearms offenses on which Kirk was ultimately indicted. The “instant offense” was one of those offenses. Thus, the district court’s application of the 3C1.1 enhancement was not error.
III. CONCLUSION
For the foregoing reasons, the appellant’s conviction and sentence are AFFIRMED.
. "Machinegun” is defined in 26 U.S.C. § 5845(b) as "any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger.”
. Fed.R.Crim.P. 48(a) provides, in relevant part, "The Attorney General or the United States attorney may by leave of court file a dismissal of an indictment, information or complaint and the prosecution shall thereupon terminate.”
. The government decided the initial prosecution should be dismissed based on the Tenth Circuit’s holding in United States v. Dalton, 960 F.2d 121 (10th Cir.1992) that the enactment of 18 U.S.C. § 922(o) implicitly repealed 26 U.S.C. § 5861(d). This Court subsequently disagreed with the Tenth Circuit on this question in United States v. Ardoin, 19 F.3d 177 (5th Cir.), cert. denied, - U.S. -, 115 S.Ct. 327, 130 L.Ed.2d 287 (1994).
. On this point, we agree with the Tenth Circuit. See United States v. Dalton, 990 F.2d 1166 (10th Cir.), cert. denied, - U.S. -, 114 S.Ct. 253, 126 L.Ed.2d 205 (1993).
. In addition, to the extent not inconsistent with the Supreme Court’s pronouncement, we are bound by our opinion in Lopez as the law of the circuit. United States v. Lopez, 2 F.3d 1342 (5th Cir.1993).
."The Constitution delegates to Congress the power ‘[t]o regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes.’” Lopez, - U.S. at -, 115 S.Ct. at 1626.
. The dissent contends that we have misconstrued the plain language of the statute in coming to this conclusion. Rather than considering the scope of the prohibition in section 922(o), the dissent prefers to discuss mere possession in a vacuum. The dissent attempts to justify its narrow perspective by noting that the offense of conviction implicated only unlawful possession, an offense distinct from unlawful transfer thanks to a disjunctive connector. The true indicator of the statute’s scope, however, is found not in subsection (1), but in subsection (2) which excludes certain transfers and possessions from the prohibitions found in subsection (1).
Following the dissent’s approach, viewing similar prohibitions against mere possession in isolation, we would be required to strike down other federal criminal statutes that thus far have heen upheld. See, for example, 21 U.S.C. § 844(a) (prohibiting simple possession of controlled substances in context of broader prohibitions against manufacture or distribution of same in the Drug Abuse Prevention and Control Act); 21 U.S.C. § 843(a)(5) (prohibiting possession of equipment designed to mark or label counterfeit drugs in context of prohibition against making or distributing same); 18 U.S.C. § 2342(a) (prohibiting possession of contraband cigarettes in context of broader prohibition against commercial transfer of same). See also 18 U.S.C. § 842(j) (prohibiting "mere” storage of any explosive material in a manner not conforming to federal regulations in context of federal restrictions on manufacture, import, purchase, and distribution of same).
. The offense to which Kirk pled guilty was unlawful "possession" of a maehinegun in violation of 18 U.S.C. § 922(o). The counts charging Kirk with unlawful "transfer” were dismissed pursuant to Kirk’s plea bargain.
. Kirk also argues that his conviction cannot be valid under the Commerce Clause because section 922(o) does not require a showing that a particular unlawful possession substantially affects interstate commerce. However, where, as here, Congress has the power to regulate a particular class of activity because of its relation to interstate commerce, there is no requirement that a substantial effect be shown in each particular case. See United States v. Nelson, 458 F.2d 556 (5th Cir.1972). Because of our holding above we need not address this argument further.
. Because of the dates of Kirk's offense conduct, and because of ex post facto considerations, the 1988 edition of the Guidelines Manual was used in this case. However, the text of section 3C1.1 as currently written does not differ in any material respect from the version applied in this case.