The U.S. Constitution specifies the enumerated powers of the federal government. These powers, however, have been interpreted broadly so as to create a large potential overlap with state authority. States may generally legislate on all matters within their territorial jurisdiction. Indeed, criminal law, family law, property, and contract and tort law, among others, are typical areas of law that are regulated at the state level. Accordingly, states have enacted their own laws regarding the unlawful possession and disposition of firearms, as well as the manner in which firearms may be carried. Congress, too, has enacted legislation related to firearms control. It includes, among others, the National Firearms Act of 1934, the Gun Control Act of 1968, the Firearm Owners' Protection Act of 1986, and the Brady Handgun Violence Prevention Act of 1993. Generally, Congress has relied on its authority under the Commerce Clause to enact such statutes. The Commerce Clause states: "The Congress shall have Power ... To regulate Commerce with foreign Nationals, and among the several States, and with Indian Tribes." Although a plain reading of the text might suggest that Congress has only a limited power to regulate commercial trade between persons in one state and persons of another state, the Clause has not been construed quite so narrowly, particularly in the modern era. Since the 1930s, the U.S. Supreme Court has held that Congress has the ability to protect interstate commerce from burdens and obstructions "no matter what the source of the dangers which threaten it." Over time, the Court concluded that Congress had considerable discretion in determining which commercial activities, including intrastate commercial activities, "affect" interstate commerce, as long as the legislation was "reasonably" related to achieving its goals of regulating interstate commerce. Furthermore, the Court in Wickard v. Filburn also held that an activity, "though it may not be regarded as commerce, it may still, whatever its nature," be regulated by Congress if, in the aggregate, "it exerts a substantial economic effect on interstate commerce." Under this prevailing interpretation of the Commerce Clause, the Supreme Court has upheld a variety of federal laws, including those regulating the production of wheat on farms, racial discrimination by businesses, and loan-sharking. However, in 1995, the Supreme Court revisited the scope of the Commerce Clause in United States v. Lopez . In Lopez , the Supreme Court held that Congress had exceeded its constitutional authority when it passed the Gun-Free School Zones Act of 1990 (School Zones Act). The Court, clarifying the judiciary's traditional approach to Commerce Clause analysis, identified three broad categories of activity that Congress may regulate under its commerce power. These are 1. the channels of commerce; 2. the instrumentalities of commerce in interstate commerce, or persons or things in interstate commerce, even though the threat may come only from intrastate activities; and 3. activities which "substantially affect" interstate commerce. Under the first two categories, Lopez endorses Congress's "power to regulate all activities, persons or products that cross state boundaries. So long as a federal regulation relates to interstate transactions or interstate transportation, the federal regulation would be justified under the first two branches.... " However, in examining the School Zones Act, the Court concluded that possession of a gun in a school zone was neither a regulation of the channels nor the instrumentalities of interstate commerce. Because the conduct regulated was considered to be a wholly intrastate activity, the Court concluded that Congress could only regulate the activity if it fell within the third category and "substantially affects" interstate commerce. The Court indicated that intrastate activities have been, and could be, regulated by Congress where the activities "arise out of or are connected with a commercial transaction" and which are "part of a larger regulation of economic activity, in which the regulatory scheme could be undercut unless the intrastate activity were regulated." The Court struck down the School Zones Act, declaring that the intrastate activity--possession of a handgun near a school--was not part of a larger economic firearms regulatory scheme. Moreover, the act did not require that interstate commerce be affected, such as by requiring the gun to be transported in interstate commerce. For the same reasons identified in Lopez , the Supreme Court subsequently invalidated a part of the Violence Against Women Act (VAWA) in United States v. Morrison . The Court in Morrison concluded that the activity regulated--a federal civil remedy for gender-motivated crimes--did not fall within the first two commerce categories, or the third category, because it was not an "economic activity"; furthermore, the provision contained no "jurisdictional element establishing that the federal cause of action [was] in pursuance of Congress's power to regulate interstate commerce." In both Lopez and Morrison , the Court rejected the government's reasoning in establishing a connection between the regulated activity and its purported effect on interstate commerce, because the Court would have been required to "pile inference upon inference in a manner that would bid fair to convert congressional authority under the Commerce Clause to a general police power of the sort retained by the States." Although finding that Congress had exceeded its authority under the Commerce Clause with respect to the laws in Lopez and Morrison , the Court in Gonzales v. Raich subsequently clarified that Congress still has considerable authority under the "substantially affects" doctrine to regulate activity that is "quintessentially economic" on the intrastate level, even though the activity itself is not a part of interstate commerce. The Court stated it did not need to determine for itself whether the activities, taken in the aggregate, substantially affect interstate commerce or undercut the larger regulatory scheme. Instead, it needed only to determine whether Congress had a rational basis to make such a conclusion. Justice Scalia, in his concurring opinion, also emphasized the role of the Necessary and Proper Clause. He opined that the Clause has been inherently relied on to regulate (1) economic intrastate activities that substantially affect interstate commerce, and (2) noneconomic intrastate activities that do not themselves substantially affect interstate commerce but that are a "necessary part of a more general regulation of interstate commerce." The latter category, however, is limited by Lopez and Morrison , where the Court rejected arguments that "Congress may regulate noneconomic activity based solely on the effect that it may have on interstate commerce through a remote chain of inferences." Although the Commerce Clause gives Congress broad authority to enact laws, there may be other constitutional constraints on its ability to regulate firearms. One constitutional limitation may be the Tenth Amendment to the U.S. Constitution, which provides: "The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people." Although the Tenth Amendment may limit the type of legislation Congress can pass, "a valid exercise of Congress' Commerce Clause power is not a violation of the Tenth Amendment." Generally, the Supreme Court has ruled that the federal government's power over interstate commerce does not authorize it to require, or commandeer, state or local governments to take legislative acts or certain executive actions. For example, in New York v. United States , the Supreme Court held that federal legislation cannot require states to develop legislation on how to dispose of all low-level radioactive waste generated within the state, nor can it order states to take title to such waste. Although the Court held that Congress had authority under the Commerce Clause to regulate low-level radioactive waste directly, such power did not authorize them to order states to enact laws. The Court subsequently held in Printz v. United States that Congress cannot commandeer state executive branch officials from carrying out a federal program, as such an act is outside Congress's power and inconsistent with the Tenth Amendment. However, the Court has upheld federal legislation that regulated state activities with respect to information obtained from drivers' license applications, because the law at issue "does not require the states in their sovereign capacity to regulate their own citizens ... [and it] does not require [the state] legislature to enact any laws or regulations, and it does not require state officials to assist in the enforcement of federal statutes regulating private individuals." The Second Amendment to the U.S. Constitution is another constitutional provision that may limit the type of legislation Congress may pass related to firearms. The Second Amendment provides: "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed." The Supreme Court in District of Columbia v. Heller held that the Second Amendment protects an individual right to keep a firearm, unconnected with service to the militia, and to use that firearm for lawful purposes such as self-defense in the home. Although Congress has the authority to regulate firearms under its commerce authority, it may not do so in a way that infringes upon the right guaranteed by the Second Amendment. Since Heller , several federal firearms laws have been challenged under the Second Amendment, though all have been upheld. For a discussion on how federal firearms laws are evaluated under a Second Amendment analysis, see CRS Report R43031, Second Amendment Challenges to Firearms Regulations Post-Heller , by [author name scrubbed]. In sum, Congress has the general authority to enact regulations under its Commerce Clause authority, so long as the activities or conduct regulated fall within one of the three categories established by Lopez . However, even where Congress may have direct authority to regulate, it cannot do so in a manner that would be inconsistent with other constitutional principles, such as those under the Tenth or Second Amendments to the U.S. Constitution. Federal firearms laws have been challenged periodically on grounds that Congress did not have authority under the Commerce Clause to pass them. This section examines lower courts' decisions regarding the constitutional validity of certain federal firearms laws, particularly the application of these laws to intrastate possession and intrastate transfer of firearms. As described above, Congress's authority under the Commerce Clause extends to regulating items that move through interstate commerce and commercial activities that affect interstate commerce. It is therefore relatively settled that Congress may regulate the manufacture and transfer of firearms. For example, the constitutionality of a federal semiautomatic assault weapons ban, which was in effect for ten years, was challenged under the Commerce Clause. In 1994, Congress passed the Violent Crime Control and Law Enforcement Act, which included a provision making it unlawful to possess, manufacture, or transfer certain types of semiautomatic pistols, rifles, and shotguns (i.e., "assault weapons"). The U.S. Court of Appeals for the District of Columbia Circuit (D.C. Circuit), in Navegar, Inc. v. United States , addressed the question of whether the activities regulated under this act fell within one of the three categories of activity identified in Lopez . Like the Court in Lopez , the D.C. Circuit determined that it was not required to analyze the act under the first or second categories because the "[it] readily falls within category 3 as a regulation of activities having a substantial [e]ffect on interstate commerce." The court analyzed individually the act's prohibitions on manufacture, transfer, and possession. Regarding the manufacturing prohibition, the D.C. Circuit declared that "[t]he Supreme Court has repeatedly held that the manufacture of goods which may ultimately never leave the state can still be activity which substantially affects interstate commerce." Regarding the prohibition on transfers, the court similarly remarked that "the Supreme Court precedent makes clear that the transfer of goods, even as part of an intrastate transaction, can be an activity which substantially affects interstate commerce." Based on these maxims, the court held that "it is not even arguable that the manufacture and transfer of 'semiautomatic assault weapons' for a national market cannot be regulated as activity substantially affecting interstate commerce." However, with respect to the possession of a semiautomatic assault weapon, the court in Navegar noted that the Lopez decision raised a question of whether "mere possession" can substantially affect interstate commerce. The court proceeded to analyze the purposes behind the act to determine whether "it was aimed at regulating activities which substantially affect interstate commerce." Analyzing the congressional hearings, the court determined that the ban on possession was "conceived to control and restrict the interstate commerce in 'semiautomatic assault weapons,'" and that the "ban on possession is a measure intended to reduce the demand for such weapons." The D.C. Circuit stated that the ban on possession was "necessary to allow law enforcement to effectively regulate the manufacture and transfers where the product comes to rest, in the possession of the receiver." Based on these factors, the court concluded that the "purpose of the ban on possession has an 'evident commercial nexus.'" Accordingly, the court held that the federal semiautomatic assault weapons ban was valid under Congress's commerce power. The Gun Control Act includes several provisions that criminalize possession of a firearm. For instance, 18 U.S.C. SS922(o) makes it unlawful for any person to "possess a machinegun" and 18 U.S.C. SS922(g) makes it unlawful for certain categories of persons to "possess in or affecting commerce, any firearm or ammunition," As demonstrated above, however, whether Congress actually has authority to regulate "mere possession" of firearms has been questioned by the courts. In particular, courts have confronted the issue of whether these provisions as applied to intrastate possession are a proper exercise of Congress's power under the Commerce Clause. Analysis regarding the validity of these federal possession provisions has varied slightly, given the development of the Supreme Court's jurisprudence on the Commerce Clause. Prior to and post- Lopez , federal courts generally upheld SS922(o) as a valid exercise of Congress's commerce power, despite the absence of jurisdictional language requiring that the machinegun travel in or substantially affect interstate commerce. However, once Lopez was decided, at least one federal court of appeals held SS922(o) to be unconstitutional as applied to a defendant who was convicted of possessing machineguns that had been home assembled through parts kits. In United States v. Stewart (Stewart I) , the U.S. Court of Appeals for the Ninth Circuit (Ninth Circuit) held that there were limits in applying SS922(o). The court rejected the argument that the statute was constitutional under either of the first two categories in Lopez , even though some of the parts of the machineguns had, at some point, moved in interstate commerce. It also found that the defendant's simple possession of homemade machineguns did not substantially affect interstate commerce as recognized by Lopez . In particular, the Ninth Circuit determined that possession of a machinegun is not, without more, economic in nature and that nothing in the legislative history indicates that the regulation itself has an economic purpose. Therefore, the court held that, as applied to the defendant's possession of homemade machineguns, SS922(o) was an unlawful extension of Congress's commerce power. Stewart I , however, was decided prior to the Supreme Court's decision in Gonzales v. Raich . Upon remand, the Ninth Circuit in Stewart II held that SS922(o) can be constitutionally applied to the defendant's possession of homemade machineguns in light of the Supreme Court's analysis in Raich . The statute at issue, as well as the actions and claims of the defendant, were "nearly identical" to the claims and statute at issue in Raich , where the Court rejected the argument that the federal provision criminalizing possession of marijuana could not be applied to the intrastate possession of medical marijuana. As discussed supra , the Court in Raich reaffirmed its prior holdings that Congress may regulate "purely intrastate activity that is not itself 'commercial' ... if it concludes that failure to regulate that activity would undercut the regulation of the interstate market in that commodity." Under this reasoning, the defendant in Raich was not successful in his attempt to carve out a class of intrastate activities as beyond the reach of Congress's commerce power. Relying on this analysis, the Ninth Circuit in Stewart II concluded that, like the regulation on possessing drugs in the Controlled Substances Act, the machinegun possession ban fits within a larger scheme for the regulation of interstate commerce of firearms. The court's new focus under the substantially affects doctrine post- Raich was "not [the defendant] and his homemade machine guns, but all homemade machineguns manufactured intrastate. Moreover, [the court] does not require the government to prove that those activities actually affected interstate commerce; we merely inquire whether Congress had a rational basis for so concluding." Thus, under this lens, machineguns, whether they are homemade or commercially made, are fungible commodities like marijuana, and Congress had a rational basis for concluding that "in the aggregate, possession of homemade machineguns could substantially affect interstate commerce in machineguns." The analysis in Raich , followed by the Ninth Circuit in Stewart II , has been relied upon by other courts in evaluating state legislation that purports to exempt from federal law the intrastate manufacture and sale of firearms, firearms accessories, and ammunition. This type of law is known as a Firearms Freedom Act. The United States District Court for the District of Montana, echoing the concerns in Raich and Stewart II , declared that "Montana's attempt to... excise a discrete local activity from the comprehensive regulatory framework provided by federal firearms laws cannot stand." In upholding the validity of the National Firearms Act and Gun Control Act as applied to the intrastate manufacture and sale of firearms and firearms accessories, the district court stated that Congress had a rational basis, without the need to have particularized findings, to conclude that failure to regulate intrastate manufacture and sale of firearms would leave a "gaping hole" in the federal scheme regulating firearms. Individuals, who have been convicted under SS922(g) for being a felon, or other prohibited person, in possession of a firearm, also have challenged whether such a provision is constitutionally valid under Congress's commerce power. For instance, the Ninth Circuit in United States v. Jones addressed the constitutional validity of SS922(g)(8), which makes it unlawful for a person who is "subject to a court order that ... [meets specific requirements] ... to ... possess in or affecting commerce, any firearm or ammunition ." The Ninth Circuit distinguished SS922(g)(8) from the School Zones Act in Lopez on the basis that this statute contains "a jurisdictional element explicitly requiring a nexus between the possession of firearms and interstate commerce." The court affirmed that this provision constitutes a valid exercise of Congress's power to regulate activity under the second and third categories identified under the Lopez framework. However, the jurisdictional hook--"in or affecting commerce"--relating to possession under SS922(g), may not be "a talisman that wards off constitutional challenges." One reason a jurisdictional hook is employed is to make facial constitutional challenges unlikely or impossible, "and to direct litigation toward the statutory question of whether, in the particular case, the regulated conduct possesses the requisite connection to interstate commerce." Notwithstanding the jurisdictional hook that distinguishes it from the School Zones Act in Lopez , an argument could be made that a felon-in-possession statute does not fall within any of the categories identified in Lopez . The U.S. Court of Appeals for the Tenth Circuit (Tenth Circuit) examined this issue in United States v. Patton , within the context of another federal statute similar to the felon-in-possession statute. In Patton , the court analyzed whether Congress had authority to prohibit the intrastate possession by a felon of a bulletproof vest, in the absence of any commercial transaction or evidence of a connection to commercial activity other than the fact that, prior to the defendant's lawful purchase, the vest had been sold across a state line. The Tenth Circuit concluded that such a provision did not fit within any of the three categories of Lopez , as clarified and affirmed by Raich , but the court nonetheless upheld the provision under a pre- Lopez precedent from the Supreme Court. After dismissing the three categories of commerce, the Tenth Circuit turned to the Supreme Court decision Scarborough v. United States , which had analyzed the pre-Gun Control Act felon-in-possession statute. Because "in or affecting commerce" applies to the word "possess," the government, in cases of pure possession, must prove that possession of a firearm has some nexus to commerce in order to validly regulate the activity. Thus, in Scarborough the Court had to determine what proof is necessary for the government to satisfy the nexus between possession and interstate commerce. The court rejected the argument that possession of the gun have some "contemporaneous connection with commerce at the time of the offense." Instead, the Court concluded that the sensible reading, supported by the legislative history, demonstrated that "Congress intended no more than a minimal nexus requirement," which may be satisfied by proving that the firearm possessed had, at some time, traveled in interstate commerce. Applying the principles from Scarborough, the Tenth Circuit in Patton upheld the constitutional validity of the body armor statute as applied to the defendant's intrastate possession, because the item, at some point, had moved across state lines and therefore such activity could be regulated under Congress's commerce power. As discussed above, a firearms possession statute, like SS922(g), may be considered a proper exercise of Congress's commerce authority under the Lopez categories. However, a reviewing court that conducts a thorough analysis of SS922(g), like the Tenth Circuit in Patton did with similar regulation, could find that mere intrastate possession of a firearm, or any firearms accessory, does not fit under any of the three Lopez categories. If so, Scarborough , which appears to have been left intact by Lopez , seems to be the controlling precedent under which the federal firearms possession statute may be enforced against prohibited intrastate possessors. One court has noted that "nothing in Lopez suggests that the 'minimal nexus' test should be changed." Notably, while courts have continued to follow Scarborough , they have also expressed doubts about its continuing validity. For example, in upholding the validity of SS922(g), the United States Court of Appeals for the Fifth Circuit opined: If the matter were res nova, one might well wonder how it could rationally be concluded that mere possession of a firearm in any meaningful way concerns interstate commerce simply because the firearm had, perhaps decades previously before the charged possessor was even born, fortuitously traveled in interstate commerce. It is also difficult to understand how a statute construed never to require any but such a per se nexus could "ensure, through case-by-case inquiry, that the firearm possession in question affects interstate commerce." [citation omitted] Several federal courts of appeals have noted the tension between Scarborough and the three-category approach later adopted by the Supreme Court. Should the Supreme Court revisit the potential doctrinal inconsistency between Lopez and Scarborough , it is conceivable that regulation of intrastate possession of a firearm or any other firearms accessory may be found to be beyond the reach of Congress. Alternatively, if the jurisdictional hook were interpreted so that the intrastate possession must have some contemporaneous connection with interstate commerce- e.g., the defendant is engaging in commerce at the time of the offense or possessing the gun at an interstate facility, then it would not be beyond Congress's commerce power to regulate some intrastate possession. The consequence of such an interpretation, however, would be that a subset of individuals would not be captured under Congress's commerce power (e.g., those who fall within a prohibited possessor category but who only maintain a firearm at home and never carry or possess it elsewhere). Another option could be to bring the wording of the current felon-in-possession statute in line with SS922(o), which lacks a jurisdictional hook. In such case, to the extent that the Supreme Court would agree with the Ninth Circuit's application of Raich in its Stewart II decision, a felon-in-possession statute without a jurisdictional hook could constitutionally apply to intrastate possession, and would appear to remove the burden on the government to satisfy the nexus requirement between possession and interstate commerce. Section 922(d)(1) of title 18 of the U.S. Code makes it unlawful for any person to dispose or transfer a firearm to another individual knowing or having reasonable cause to believe that such person is under indictment for, or has been convicted in any court of, a crime punishable by more than one years' imprisonment. Individuals who have been convicted under this provision for making unlawful transfers intrastate have contended that Congress exceeded its authority under the Commerce Clause by enacting this provision. Such challenges have proven unsuccessful. For instance, the U.S. Court of Appeals for the Sixth Circuit (Sixth Circuit) in United States v. Rose held that this contention "lacks merit inasmuch as the Supreme Court precedent leaves no doubt regarding the constitutionality of SS922(d)(1)." The Sixth Circuit analyzed this provision under the third Lopez category--the substantially affects doctrine--and concluded that the Raich analysis leads to the conclusion that SS922(d)(1) is proper use of Congress's commerce power. The Sixth Circuit stated that guns, similar to marijuana, are a "fungible commodity" for which there is an established interstate market and that the provision at issue is a part of the larger regulatory framework. The court concluded that the relevant "legislative history supports the logical connection between the intrastate sale and disposition of firearms and interstate market in firearms." As part of the regulatory framework for ensuring that firearms are not transferred to those persons deemed to be prohibited under federal law, Congress passed the Brady Handgun Violence Prevention Act of 1993 (Brady Act), which requires federal firearms licensees (FFLs) to conduct a background check on prospective firearms purchasers through the National Instant Criminal Background Check System (NICS). However, prior to the establishment of NICS, the Brady Act's interim provisions required the chief law enforcement officers within a state to conduct a background check on a prospective firearms purchaser within five business days. This portion of the act was invalidated on Tenth Amendment grounds in Printz v. United States under the theory that Congress was without authority to order or "commandeer" state executive branch officials. The holding in Printz indicates that although the Tenth Amendment limits the way in which Congress can implement background checks, it is not beyond its commerce power to require such checks as part of transferring a firearm. Under the current scheme, FFLs are required to conduct a background check through NICS before transferring a firearm to any non-FFL, including those who reside within the state in which the FFL is located. Currently, Congress is considering legislation that would impose a background check on transactions between non-FFLs that occur within a state. Just as Congress's authority to regulate intrastate transfers has been challenged, one might question whether Congress has the authority to require, or impose a requirement, that FFLs or non-FFLs conduct a background check on intrastate firearms transactions. Based on the Court's holdings in Lopez and Raich , discussed above, it seems that requiring a background check on intrastate firearms transactions is unlike regulating simple possession of firearms in a school zone. Although the act of conducting a background check may not be itself "commercial," it is a condition on the commercial transfer of a firearm. Therefore, if such a measure were enacted, it seems that there would be a substantial basis upon which a court could regard it as a provision supporting the larger regulatory scheme--the Gun Control Act--that Congress enacted to "keep firearms out of the hands of those not legally entitled to possess them because of age, criminal background, or incompetency, and to assist law enforcement authorities in the states and their subdivisions in combating the increasing prevalence of crime in the United States." Congress has broad authority pursuant to the Commerce Clause to enact laws in areas that may overlap with traditional state jurisdiction. As such, Congress has passed complex statutory provisions that regulate the possession, receipt, transfer, and manufacture of firearms and ammunition. Notwithstanding this broad authority, Congress may not exceed other constitutional provisions or doctrines, such as the Tenth or Second Amendments to the U.S. Constitution. Thus, Congress may not pass legislation that infringes on the right guaranteed by the Second Amendment, nor may it pass legislation that orders state legislatures or its officials to implement and perform a federal law or program. Outside these types of limitations, exercise of Congress's commerce power appears to be proper as long as the regulated activity or conduct falls within one of the three categories established by the Supreme Court in United States v. Lopez , that is, (1) the channels of interstate commerce; (2) the instrumentalities of interstate commerce, including persons and things; and (3) activities that substantially affect interstate commerce. As explored in this report, courts have been confronted with the question of whether federal laws can be applied to intrastate possession and intrastate transfers of firearms, or whether such application exceeds the authority of Congress under its commerce power. Generally, the courts have upheld such laws under these as-applied challenges. With respect to intrastate possession, there remains noticeable tension between the Commerce Clause analysis set forth in Lopez and the pre- Lopez Supreme Court precedent that is still relied on by lower courts to uphold regulations on the possession of firearms. It is unclear how Congress's authority to regulate firearms possession would be affected should the Supreme Court resolve any perceived doctrinal inconsistency. Furthermore, the Supreme Court's analysis in Gonzales v. Raich has also buttressed the reasoning by which lower courts have concluded that Congress's authority to regulate firearms extends to intrastate manufacture and intrastate transfers and, as such, states cannot exempt themselves from federal regulation.

Summary:
Congress has broad authority pursuant to the Commerce Clause to enact laws in areas that may overlap with traditional state jurisdiction. As such, Congress has passed complex statutory provisions that regulate the possession, receipt, transfer, and manufacture of firearms and ammunition. Generally, courts have upheld the validity of firearms laws pursuant to Congress's commerce power. However, courts have been confronted with the question of whether federal laws can be applied to intrastate possession and intrastate transfers of firearms, or whether such application exceeds the authority of Congress. This report explores these cases and how courts have analyzed these as-applied challenges under the Supreme Court's Commerce Clause jurisprudence primarily set forth in United States v. Lopez.