Introduction

The federal government is a creature of the Constitution. It enjoys no authority that cannot be traced back to the Constitution. This is as true of Congress as of the other branches. Although the Constitution grants Congress extensive legislative powers, it vests Congress with explicit authority to enact criminal law in only three places. Article I, Section 8, clause 6 states that "Congress shall have Power ... To provide for the Punishment of counterfeiting the Securities and current Coin of the United States." A few lines later, the Constitution gives Congress authority over three additional classes of crime, when it declares that "Congress shall have Power ... To define and punish Piracies and Felonies committed on the high Seas, and Offenses against the Law of Nations." Finally, the Constitution defines the crime of treason, but empowers Congress to set its punishment.
A casual reader might conclude that Congress may enact no other class of criminal statutes. After all, the Tenth Amendment denies Congress any authority that the Constitution does not grant it. Upon closer examination, however, it becomes clear that the Constitution elsewhere gives Congress, the President, and the federal courts sweeping powers. Moreover, the authority it places in the hands of Congress includes an implementing power, that is, the authority to enact laws necessary and proper to the implementation of those other powers—authority that by implication includes the authority to enact reasonably related criminal laws.
Nevertheless, Congress's criminal law enacting powers are not boundless. Some limitations reside with the grant of authority. Article III, for example, allows Congress to set the punishment for treason, but denies it permission to punish treason with corruption of the blood. The Constitution mentions other limitations in areas apart from its grants of authority, like the prohibition on ex post facto laws or abridgement of freedom of speech. The third class of limitations is more difficult to discern. Whether understood as contextual, or structural, or implicit in the Tenth Amendment, they are the limitations of federalism, the limitations that flow from the fact the Constitution emerged as a compact between the sovereign it created and the sovereigns that created it.
What follows is a discussion of selected recent cases that illustrate the scope and boundaries of Congress's power to enact criminal laws under the Constitution's necessary and proper, commerce, high seas, law of nations, spending, and military clauses.

	Necessary and Proper Clause

The Congress shall have Power ... To make all Laws which shall be necessary and proper for carrying into Execution the foregoing Powers, all other Powers vested by this Constitution in the Government of the United State, or in any Department or Officer there.
"[T]he Necessary and Proper Clause makes clear that the Constitution's grants of specific federal legislative authority are accompanied by broad power to enact laws that are 'convenient or useful' or 'conductive' to the authority's 'beneficial exercise.'" The phrase "necessary and proper" does not demand absolute necessity. It is enough that a statute is rationally related to the constitutional power it seeks to "carry into execution."
The Supreme Court's Comstock decision offered an expansive view of the Necessary and Proper Clause, with caveats. Two Sex Offender Registration and Notification Act (SORNA) cases, Kebodeaux and Elk Shoulder , treat the caveats and thus the scope of the Clause very differently. Two other recent appellate decisions, Bond and Belfast , raise questions of the Tenth Amendment limits, if any, on congressional authority under the Clause. The Supreme Court has granted certiorari in Bond and Kebodeaux . 

		United States v. Comstock

The Supreme Court in Comstock stated that a statute that relies on the Necessary and Proper Clause need not always be but one step removed from the constitutional power it brings to life. Comstock and his fellow petitioners challenged the constitutional underpinning of 18 U.S.C. 4248. Section 4248 authorizes federal courts to order the civil commitment of federal inmates whose release is imminent on the grounds that the prisoners are mentally ill and sexually dangerous.
The Court did not rule upon whether Section 4248 was a necessary and proper means of carrying into execution the Commerce Clause pursuant to which the statute of Comstock's conviction had been enacted. Instead of reference to the Commerce Clause, it began with the observation that, other than in the case of piracy and other constitutionally identified crimes, the enactment of criminal statutes generally occurs by operation of the Necessary and Proper Clause. It then identified the links in the chain that began with the constitutional authority to enact criminal laws and ended with Section 4248. Section 4248, it held, "is a 'necessary and proper' means of exercising the federal authority that permits Congress to create federal criminal laws, to punish their violation, to imprison violators, to provide appropriately for those imprisoned, and to maintain the security of those who are not imprisoned but who may be affected by the federal imprisonment of others." 
The Comstock Court confirmed, however, that a statute cannot be "proper" if it is constitutionally prohibited or inconsistent with the letter or spirit of the Constitution. The Court listed five considerations upon which its decision was predicated. Although it did not say so, the implication is that without the five, the Court might have found Section 4248 inconsistent with the spirit of federalism that permeates the Constitution. The five were
(1) the breadth of the Necessary and Proper Clause, (2) the long history of federal involvement in arena [of the mental health of federal prisoners], (3) the sound reasons for the statute's enactment in light of the Government's custodial interest in safeguarding the public from dangers posed by those in federal custody; (4) the statute's accommodation of state interests [e.g., the statute demands that federal custody of the committed inmate be surrendered when the appropriate state expresses a willingness to assume responsibility], and (5) the statute's narrow scope.

		SORNA Cases

The United States Court of Appeals for the Fifth Circuit and the United States Court of Appeals for the Ninth Circuit read the Comstock five considerations differently. The Fifth Circuit, sitting en banc in United States v. K ebodeaux , applied the considerations and found the Necessary and Proper Clause insufficient to support the application of the Sex Offender Registration and Notification Act (SORNA) to a fully discharged federal sex offender. The Ninth Circuit, in United States v. Elk Shoulder , applied the same considerations and came to opposite conclusions in the case of a federal sex offender still under supervised release. 
While a 21-year-old soldier, Kebodeaux was court martialed for engaging in consensual sex with a 15-year-old. Some years after his release and discharge, Congress enacted SORNA, which required federal sex offenders to register with state authorities and to maintain the currency of their registrations. Shortly thereafter, the Attorney General exercised his statutory authority to impose the obligation upon those who had been convicted of federal offenses prior to SORNA's passage. Then, Kebodeaux moved from El Paso to San Antonio within the state of Texas without reporting his relocation to state authorities. He was convicted under 18 U.S.C. 2250(a) for the failure.
Elk Shoulder was convicted of sexually abusing a six-year-old within the territorial jurisdiction of the United States in violation of 18 U.S.C. 2241(c). He had been released from prison, but was on supervised release when SORNA was enacted. He moved from place to place in Montana, but never registered and was subsequently convicted under 18 U.S.C. 2250(a) for the failure. 
Both Circuits agreed that the Comstock decision provides the proper mode of analysis for challenges grounded in the Necessary and Proper Clause. Their respective views of the Comstock considerations differ dramatically thereafter. First, the Fifth Circuit conceded that the Necessary and Proper Clause vests Congress with broad authority. The Ninth Circuit went a step further and concluded that "SORNA was rationally related to an enumerated power" (the power to enact legislation governing activities within the territorial jurisdiction of the United States). 
Second, the Comstock Court noted that the civil commitment statute at issue was "a modest addition to a set of federal prison-related mental-health statutes that have existed for many decades." The Ninth Circuit stated that in like manner SORNA was a modest addition to the federal parole, probation, and supervised release laws that date back to 1910. SORNA and those provisions both deal with the post-incarceration supervision. The Fifth Circuit found SORNA historically novel. It found the probation-supervised release analogy wanting because, unlike SORNA, both probation and supervised release are part of the punishment for the original federal offense crime. Although failure to comply is a crime, SORNA's registration demands are not considered punitive. Moreover, SORNA did not exist until long after Kebodeaux had served his sentence.
In its third consideration, the Comstock Court highlighted the sound policy reasons for the statute's enactment (protection of the public from those in federal custody). In the mind of the Ninth Circuit, the Comstock statute authorized civil commitment to protect the public from federal sex offenders, while SORNA required registration to protect the public from federal sex offenders. Both were reasonably adapted to a legitimate end. The Fifth Circuit disagreed. It believed that custodial responsibility for those soon to be released differs from custodial responsibility for those released long ago. The difference prevented the Fifth Circuit from classifying SORNA's application to Kebodeaux as reasonably related to a constitutional power.
The Fourth Comstock consideration is the accommodation of state interest. The Comstock statute allowed the appropriate state to assume jurisdiction over soon-be-released prisoners whom federal authorities would otherwise subject to federal civil commitment. The Ninth Circuit found at least equivalent accommodation in SORNA. It does not supplant the state systems. Its criminal penalties only apply with respect to state sex offenders who travel in interstate commerce or to federal sex offenders. Its encouragement of state acceptance of federal standards is modest. The Fifth Circuit, on the other hand, viewed SORNA as less accommodating than the Comstock statute. Unlike the Comstock statute, SORNA gives state authorities no option to substitute state discretion for that of federal authorities. 
Finally, the Comstock Court observed that the regulatory scheme under consideration was neither too remote from the enumerated power upon which it relied nor too sweeping in scope. The same could be said of SORNA, the Ninth Circuit asserted. Again, the Fifth Circuit took a different view: the government's rationale in defense of SORNA—that federal conviction vests Congress with boundless, timeless legislative authority over the individual—"is anything but narrow." 
The Fifth Circuit concluded that SORNA, as applied to Kebodeaux, failed to satisfy the Comstock considerations and consequently exceeded Congress's authority under the Necessary and Proper Clause. The Ninth Circuit, writing after the Fifth Circuit's opinion had been announced, explicitly disagreed with it: "Because we reject the Fifth Circuit's conclusion that Congress cannot 'reassert jurisdiction over someone it had long ago unconditionally released from custody,' a proposition for which the Fifth Circuit provided no support, we disagree with its analysis of the Comstock considerations, which is based almost exclusively on that conclusion."

		United States v. Bond

The Bond decision addressed the question of whether structural, federalism concerns limit congressional authority under the Necessary and Proper Clause to enact treaty implementing legislation. Mrs. Bond sought revenge against her husband's paramour by coating the woman's car door handles and door knobs with toxic chemicals. Mrs. Bond was convicted of using a chemical weapon in violation of the Chemical Weapons Implementation Act. She argued on appeal that either the statute did not apply to her conduct or that Congress lacked the constitutional authority to enact legislation that swept into federal court a local "run of the mill" assault case, like her own. The Third Circuit Court of Appeals initially held that Mrs. Bond had no standing to challenge her conviction on federalism grounds, maintaining that only a state could object to intrusion upon its sovereign prerogatives. The Supreme Court reversed. Mrs. Bond may claim the benefits of federalism, since it "secures to citizens the liberties that derive from the diffusion of sovereign power."
When the case returned to the Third Circuit for a decision on the merits, the court was faced with the question of the extent to which principles of federalism limit congressional authority under the Necessary and Proper Clause to implement a United States treaty. The Supreme Court appeared to have provided the answer in Missouri v. Holland . There, in the face of a federalism objection, the Court declared that "[i]f the treaty is valid there can be no dispute about the validity of the statute under Article I, Section 8, as a necessary and proper means to execute the powers of the Government." 
In theory, a treaty may be invalid in three ways. First, it may exceed the authority granted in the Treaty Power. Second, it may exceed an express limitation that appears elsewhere in the Constitution. Finally, it may exceed an implicit constitutional limitation. As to the first, the Holland Court considered the Migratory Bird Treaty subject matter properly attributed to the Treaty Power: it constituted a matter of national concern that could "be protected only by national action in concert with that of another power." Second, the Migratory Bird Treaty "[did] not contravene any prohibitory words to be found in the Constitution." Therefore, "[t]he only question [was] whether [the Migratory Bird Treaty was] forbidden by some invisible radiation from the general terms of the Tenth Amendment."
The Holland Court answered this last question by comparing the strength of the competing state and federal claims. Missouri's claim rested on a "slender reed. Wild birds are not in possession of anyone; and possession is the beginning of ownership. The whole foundation of the State's rights is the presence within [its] jurisdiction of birds that yesterday had not arrived; tomorrow may be in another State and in a week a thousand miles away."
The federal interest, on the other hand, was substantial:
Here a national interest of very nearly the first magnitude is involved. It can be protected only by national action in concert with that of another power. The subject-matter is only transitorily within the State and has no permanent habitat therein. But for the treaty and the statute there soon might be no birds for any powers to deal with. We see nothing in the Constitution that compels the Government to sit by while a food supply is cut off and the protectors of our forests and our crops are destroyed. It is not sufficient to rely upon the States. The reliance is vain, and were it otherwise, the question is whether the United States is forbidden to act. We are of [the] opinion that the treaty and statute must be upheld. 
In the Third Circuit upon return, Mrs. Bond conceded the validity of the Chemical Weapons Convention. She argued instead that the Constitution imposes explicit and implicit limits on congressional authority under the Necessary and Proper Clause. "The problem with [Mrs.] Bond's attack," in the eyes of the Third Circuit, was "that, with practically no qualifying language in Holland to turn to" the court was "bound to take at face value the Supreme Court's statement that '[i]f the treaty is valid there can be no dispute about the validity of the statute ... as a necessary and proper means to execute the powers of the Government.'" Nor was the court convinced that the implementing statute "disrupts the balance of power between the federal government and the states," the argument at the heart of Mrs. Bond's challenge.
The court was not unsympathetic to Mrs. Bond's contention that her case did not belong in federal court: Mrs. "Bond's prosecution seems a questionable exercise of prosecutorial discretion, [The decision to use the Act—a statute designed to implement a chemical weapons treaty—to deal with a jilted spouse's revenge on her rival is, to be polite, a puzzling use of the federal government's power], and indeed appears to justify her assertion that this case 'trivializes the concept of chemical weapons.'" A concurring member of the panel was even more critical and expressed the hope that the Supreme Court would accept the case for review. The Court has done so.

		United States v. Belfast

The Belfast decision addressed the question of whether due process limits Congress's treaty implementing authority. The United States District Court for the Southern District of Florida convicted Belfast of overseas violations of the Torture Act, a statute enacted to implement the Convention Against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment (CAT). Belfast argued that the Torture Act exceeded congressional authority under the Treaty Power and Necessary and Proper Clauses, because it outlawed conspiracy when the Convention did not mention and because the statute included a more sweeping definition of torture. On appeal, the Eleventh Circuit Court of Appeals concluded that "[a]pplying the [Necessary and Proper Clause's] rational relationship test in this case, we are satisfied that the Torture Act is a valid exercise of congressional power under the Necessary and Proper Clause, because the Torture Act tracks the provisions of CAT in all material respects." 
Since the violations occurred overseas, the threat to state law enforcement interests was minimal and posed no restriction on congressional authority. Nevertheless, the Constitution confines congressional authority both explicitly and implicitly for the protection of the people of the United States. 
Belfast asserted that the absence of CAT ratification by the nation where the torture occurred denied him the notice of its application to him which due process required. The court was unconvinced. It reminded him that "[t]he Supreme Court made clear long ago that an absent United States citizen is nonetheless 'personally bound to take notice of the laws [of the United States] that are applicable to him and to obey them.'" The issue of structural limitations did not arise. 

	Commerce Clause

The Congress shall have Power ... To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes. 

		Interstate Commerce

The classic statement of Congress's legislative power under the Interstate Commerce Clause appears in United States v. Lopez , United States v. Morrison , and Gonzales v. Raich . There the Court points out that the Clause grants Congress authority to enact three classes of statutes. "First, Congress may regulate the use of the channels of interstate commerce," as it has done when it outlawed the interstate transportation of stolen property or the interstate transportation of kidnap victims. "Second, Congress is empowered to regulate and protect the instrumentalities of interstate commerce, or persons or things in interstate commerce, even though the treat may come only from intrastate activities," as it has done when it outlawed the destruction of aircraft or the theft of property from interstate shipment. "Finally, Congress' commerce authority includes the power to regulate those activities having a substantial relation to interstate commerce," as it has done when it outlaws cultivation and possession of controlled substances.
In New York v. United States , the Court noted that Congress could not rely on the Commerce Clause to commandeer the legislative and regulatory processes of the states in order to enforce a federal program for the disposal of radioactive waste. This is no less true when a statute offers the states a choice of two unpalatable alternatives—federal commandeering or taking title to radioactive waste. The Court explained in Printz v. United States that by the same token, Congress could claim no Commerce Clause or Necessary and Proper Clause authority to compel state law enforcement officials to conduct background checks on prospective handgun purchasers as part of a federal regulatory program.
Moreover, the Court held in Lopez that the Commerce Clause did not empower Congress to enact statutes that outlawed possession of a firearm in a school yard and in Morrison that it does not permit creation of a federal cause of action for the victims of violent, gender-based animus. The Clause does not enable any such attempt to regulate activities without a more immediate relation to commerce, particularly if the activities are markedly local. This is not to deny, as the Court acknowledged in Raich , that Congress may regulate intrastate activity such as the cultivation and possession of marijuana that has a substantial impact on a class of interstate commercial activity such as the interstate and international traffic in marijuana. 
Seven National Federation of Independent Business justices found the Patient Protection and Affordable Care Act's individual mandate more than the Interstate Commerce Clause empowers. The Kebodeaux court found the outer reaches of the Sex Offender Registration and Notification Act (SORNA) beyond Congress's power under the Interstate Commerce Clause as well as the Necessary and Proper Clause. 

			National Federation of Independent Business v. Sebelius

A confluence of views, rather than a holding, in National Federa tion of Independent Business v. Sebelius , appears to identify a previously unannounced limitation on the congressional power under the Interstate Commerce Clause: the Clause does not empower Congress to penalize the failure to engage in commerce.
The question involved the so-called individual mandate feature of the Patient Protection and Affordable Care Act. The individual mandate, with some exceptions, requires healthy individuals, who might otherwise forgo purchasing health insurance, to obtain insurance or to pay a penalty. The provision is designed to compensate insurers for their required coverage of certain unhealthy individuals. Although a majority of the Court found that the mandate is the valid exercise of Congress's constitutional taxing power, seven Justices—three members of the majority and four dissenters—stated that the Commerce Clause afforded insufficient constitutional authority for its enactment. Chief Justice Roberts, joined by Justices Breyer and Kagan, observed that the power to regulate commerce does not include the power to require individuals to engage in commerce. The four dissenters struck much the same cord when they noted: "The Individual Mandate in the Act commands that every individual shall ... ensure that the individual ... is covered under minimum essential coverage. If this provision 'regulates' anything, it is the failure to maintain minimum essential coverage.... But that failure—that abstention from commerce—is not 'Commerce.' To be sure, purchasing insurance is 'Commerce'; but one does not regulate commerce that does not exist by compelling its existence." However, the dissenters' opinion was grounded also on the principle that "Whatever may be the conceptual limits upon the Commerce Clause ... [it] cannot be such as will enable the Federal Government to regulate all private conduct...."
The case did not involve enactment of a criminal statute. However, the scope of the Commerce Clause defines the scope of congressional authority to enact implementing criminal legislation.

			United States v. Kebodeaux

Having concluded that application of SORNA in the case before it exceeded Congress's Necessary and Proper powers, the Fifth Circuit in Kebodeaux also rejected the suggestion that SORNA, as applied, might be considered a valid exercise of Congress's Commerce Clause powers under the "channels of commerce," the "instrumentalities of commerce," or the "substantial effect on commerce" prong of the Clause. It held that "Congress lacks the constitutional authority under the 'channels of interstate commerce' to require fully discharged former federal sex offenders to register whenever they relocate within a state, because it risks the use of interstate travel by sex offenders; nor under the protecting the instrumentalities of interstate commerce because sex offenders may pose a risk to interstate traffic if they travel interstate." The Fifth Circuit concluded that the justifications were too sweeping and too intrusive upon state criminal law prerogatives. As for the substantial impact on commerce prong, the Fifth Circuit thought SORNA, as applied, looked too much like the regulation of non-economic activity in Lopez and Morrison and too little like the regulation of "quintessentially economic activity" in Raich . 

		Foreign Commerce

A disagreement has recently developed in the lower federal appellate courts over whether the Lopez Interstate Commerce Clause standards relating to commercial channels, instrumentalities, and effects apply with equal force to the Foreign Commerce Clause. A few years ago, the Ninth Circuit stated that congressional authority under the Foreign Commerce Clause could be defined without reference to the Lopez standards. More recently, the Third Circuit expressly questioned that approach. In between, the Second Circuit sidestepped the question with a statutory construction that avoided the constitutional issues, a construction Congress may have had in mind when it expanded a related proscription in reauthorization of the Violence Against Women Act. 

			United States v. Clark

Clark, an American expatriate, lived in Cambodia but about once a year returned to the United States for family and business reasons. Clark was convicted under 18 U.S.C. 2423(c) for traveling in foreign commerce and engaging in commercial sexual activity with children under the age of 18 in Cambodia. Clark appealed, arguing among other things, that his conduct rested beyond the outer limits of the Foreign Commerce Clause. The Ninth Circuit held that "[t]he combination of Clark's travel in foreign commerce and his conduct of an illicit commercial sex act in Cambodia shortly thereafter puts the statute squarely within Congress's Foreign Commerce Clause authority. In reaching this conclusion, we view the Foreign Commerce Clause independently from its domestic brethren." A dissenting member of the panel objected that the Foreign Commerce Clause should not be read to permit Congress to regulate all commercial activities once an individual has engaged in international travel.

			United States v. Weingarten

Weingarten, another American expatriate, sexually abused his daughter for years. He was eventually convicted for transportation of a child with intent to engage in unlawful sexual activity in violation of 18 U.S.C. 2423(a) and for travel in foreign commerce with the intent to engage in unlawful sexual activity with a child in violation of 18 U.S.C. 2423(b). A flight between Belgium and Israel formed the basis of one of the foreign commerce counts. On appeal, Weingarten argued alternatively that (1) travel between two foreign countries without a nexus to the United States could not meet the statutory requirement of "travel in foreign commerce," or (2) if the statute purported to do so, it exceeded congressional authority under the Foreign Commerce Clause.
The Second Circuit opted to construe the statute so that it did not apply to travel between foreign countries with no nexus to the United States. Constitutional avoidance, however, seems to have played a role in the court's election. 

			United States v. Pendleton

Pendleton flew from New York to Germany where he sexually assaulted a child. He was convicted of traveling in foreign commerce and engaging in unlawful sexual activity with a child in violation of 18 U.S.C. 2423(c). He challenged the constitutional authority of Congress to rely on the Foreign Commerce Clause to enact a statute that punishes noncommercial overseas sexual activity.
The Third Circuit disagreed. Although it declined the government's invitation to endorse the Ninth Circuit's Clark decision, it found it need not resolve the issue. The facts before it satisfied Lopez's "channels of commerce," making it unnecessary to decide whether the Foreign Commerce Clause reaches areas not covered by the Interstate Commerce Clause's channels, instrumentalities, and affects standards. Congress enjoys constitutional authority to prevent the use of the channels of commerce for purposes of illicit sex tourism, the Third Circuit held. 

			VAWA Reauthorization

The Violence Against Women Reauthorization Act of 2013 amends Section 2423(c) to permit prosecution of American expatriates who engage in unlawful sexual conduct overseas without the need to establish travel in foreign commerce: "Any United States citizen or alien admitted for permanent residence who travels in foreign commerce or resides either temporarily or permanently in foreign country , and engages in any illicit sexual conduct with another person shall be fined under this title or imprisoned not more than 30 years, or both."

	Article I, Section 8, Clause 10

The Congress shall have Power ... To define and punish Piracies and Felonies committed on the high Seas, and Offenses against the Law of Nations.
Clause 10 is said to contain three distinct components: one for piracy, one for felonies committed upon the high seas, and one for offenses against the law of nations. The Bellaizac-Hurtado court's understanding of the Law of Nations Clause leaves Congress with little discretion to "define and punish." The Dire court's construction of the piracy statute leaves the scope of the Piracy Clause somewhat uncertain. On the other hand, once due process concerns are resolved, Congress seems to be thought to enjoy much greater legislative latitude under the High Seas Clause, as evidenced by cases decided under the Maritime Drug Law Enforcement Act (MDLEA) and the Drug Trafficking Vessel Interdiction Act (DTVIA), 

		Law of Nations

			United States v. Bellaizac-Hurtado

Panamanian authorities arrested Bellaizac-Hurtado and his co-defendants after they abandoned in Panamanian waters an unflagged vessel containing 760 kilograms of cocaine. A federal grand jury subsequently indicted them under the Maritime Drug Law Enforcement Act (MDLEA) for possession of cocaine, with intent to distribute, aboard a vessel subject to United States jurisdiction. They pleaded guilty, but reserved the right to appeal the questions of congressional power to authorize their convictions under the Piracy, High Seas, and Law of Nations Clause. The court determined that congressional authority under the Law of Nations Clause did not extend to a prohibition of drug trafficking within the territorial waters of another nation. 
The court's analysis began with the proposition that Congress's authority to "define and punish ... Offenses against the Law of Nations" does not include the authority to define what constitutes an offense under the law of nations. "Whether the offense as defined is an offense against the law of nations depends on the thing done, not on any declaration to that effect by congress." It then decided that an offense must be contrary to customary international law in order to constitute an offense against the law of nations. Customary international law, the court said, is that law which is generally and consistently practiced by nations throughout the world out of a sense of legal obligation. 
Drug trafficking, the offense at issue, was not recognized as contrary to customary international law when the Law of Nations Clause was drafted nor has since acquired that status, the court stated. Although most nations have endorsed treaties obligating them to suppress drug trafficking, the court cited evidence that the practice in many nations belies any assertion that they feel compelled to do so out of a sense of legal obligation. 
The Bellaizac-Hurtado court had little Supreme Court jurisprudence upon which to build. Although not relevant for the court's analysis, the only Supreme Court decision directly on point suggests that Congress's power under the Law of Nations Clause may be slightly more robust in other contexts: "The law of nations requires every national government to use 'due diligence' to prevent a wrong being done within its own dominion to another nation with which it is at peace, or to the people thereof." 

		High Seas

The High Seas Clauses cases primarily arise out of the Maritime Drug Law Enforcement Act (MDLEA) and more recently out of the Drug Trafficking Vessel Interdiction Act (DTVIA). Early on, the lower federal appellate courts concluded that Congress's power "to define and punish Piracies and Felonies committed on the High Seas, and Offences against the Law of Nations" vested it with authority to enact MDLEA. Some also recognized a due process limitation on the courts' ability to try and punish MDLEA defendants. The DTVIA cases continue this line of reasoning.

			The DTVIA Cases

				United States v. Ibarguen-Mosquera

Ibarguen-Mosquera was convicted of operating an unflagged, semi-submersible vessel in international waters in violation of the Drug Trafficking Vessel Interdiction Act (DTVIA). He argued unsuccessfully that DTVIA exceeded congressional authority under Article I, Section 8, and violated due process.
The court dispensed with the first contention quickly by pointing to Congress's authority under the High Seas Clause. Its sole remaining concern was any due process limitation on Congress's ability to reach foreign nationals traveling outside U.S. territorial waters. The lower federal appellate courts generally conclude that the demands of due process have been satisfied, if the assertion of jurisdiction is consistent with international law. For this, the court cited its precedents and those of some of the other circuits which have consistently held that unflagged, stateless vessels enjoy no right to freely travel the high seas. 

				United States v. Saac

Saac was likewise convicted under DTVIA, and he too challenged its constitutionality. The court referred to the High Seas Clause and noted that the Clause did not explicitly confine its scope to either U.S. territorial waters or U.S. citizens. The court disposed of the due process argument with the observation that the DTVIA is consistent with the due process satisfying principles of international law that allow a country to enact laws against universally condemned misconduct (e.g., drug trafficking), and against threats to its national security (e.g., smuggling).

			United States v. Cardales-Luna

Cardales-Luna was convicted under MDLEA after U.S. Coast Guard officials interdicted his Bolivian-registered vessel on the high seas and discovered that it contained 400 kilograms of cocaine. Bolivian authorities consented to the application of MDLEA aboard the vessel, thereby satisfying MDLEA's "vessel within the jurisdiction of the United States" requirement. The court did not address the issue of Congress's legislative authority, since neither Cardales-Luna nor the government raised the issue.
A dissenting member of the panel, however, would have done so. Judge Torruella contended that "the application to MDLEA to Appellant [constitutes an] ultra vires extension of [Congress'] Article I legislative powers to foreign territory, as applied to persons and/or activities that have no nexus with the United States." Moreover, he suggested that "the question of Congress exceeding its Article I power under the facts of this [MDLEA] case is structural in nature and [therefore] cannot be waived by the individual concerned or the nation of which he is a citizen or on whose vessel he is apprehended."
In the course of his analysis, Judge Torruella examined and rejected several possible sources of congressional authority. He found power under the Piracy, High Seas, and Law of Nations Clause wanting because he understood the Clause confined to piracy, slave trading, and offenses contrary to customary international law. Implementation of the maritime jurisdiction of the federal courts demands an American vessel. Implementation of the Treaty Clause requires a treaty. The Foreign Commerce Clause demands a "demonstrable and direct nexus to the United States." 

		Piracy

			United States v. Dire

Dire was convicted of piracy under 18 U.S.C. 1651 following his participation in an armed attack on a U.S. Navy frigate that he believed to be a merchant ship. The Fourth Circuit acknowledged that Congress has the constitutional authority to define and punish piracy. Section 1651 outlaws piracy "as defined by the law of nations." This, the court concluded, means piracy as understood by customary international law at the time of the offense.

	Spending Clause

The Congress shall have Power To lay and collect Taxes ... to provide ... for the general Welfare of the United States.
The Supreme Court has said in the past that Congress's exercise of the Spending Clause is subject to certain limitations: "[F]irst[,] ... the exercise of the spending power must be in pursuit of 'the general welfare.' ... Second, ... if Congress desires to condition the States' receipt of federal funds, it must do so unambiguously enabling the States to exercise their choice knowingly, cognizant of the consequences of their participation. Third, ... conditions on federal grants might be illegitimate if they are unrelated to the federal interest in particular national projects or programs.... Finally, ... other constitutional provisions may provide an independent bar to the conditional grant of federal funds." National Federation brings home the point that Congress may not use its spending power to coerce state participation in a federal program.

		National Federation of Independent Business v. Sebelius

The Patient Protection and Affordable Care Act purported to condition the continued receipt of federal Medicaid funds upon a state's participation in an expanded Medicaid program. Seven Justices of the Court—three from the majority and four dissenters—felt that was more than the Spending Clause conveys. Coercion doomed the effort. Congress may employ the power of the purse to encourage the states to participate in a federal program; it may not use it to compel them to do so. The dissenters pointed out that "'the legitimacy of Congress' power to legislate under the spending power ... rests on whether the State voluntarily and knowing accepts' [a condition].... Congress effectively engages in [] impermissible compulsion when state participation in a federal spending program is coerced, so that the States' choice whether to enact or administer a federal regulatory program is rendered illusory." 
Chief Justice Roberts, in the portion of his opinion joined by Justices Breyer and Kagan, made the same point. Neither he nor the dissenters found it necessary to mark precisely where persuasion becomes coercion. Wherever the line, the Medicaid expansion was beyond it.
Again, National Federation did not involve a criminal statute, but the scope of the power defines the scope of power to enact criminal laws in its implementation.

	Military Clauses

The Congress shall have Power ... To declare War ... To raise and support Armies ... To provide and maintain a Navy; To make Rules for the Government and Regulation of the land and naval Forces ... To provide for organizing, arming, and disciplining the Militia....

		United States v. Brehm

Brehm, a foreign national and Department of Defense (DOD) contractor, assaulted another foreign DOD contractor at Kandahar Airfield in Afghanistan. He was brought to the United States and convicted of assault resulting in serious bodily injury under the Military Extraterritorial Jurisdiction Act (MEJA). Brehm argued that the Constitution gave Congress no authority to outlaw altercations between foreign nationals outside the United States and that due process precluded any effort to do so. The Fourth Circuit concluded that the Military Clauses supplemented by the Necessary and Proper Clause supplies all the constitutional authority required. As for due process limitations, the circumstances and the nature of his conduct afforded Brehm fair notice that his dangerous assault exposed him to prosecution.

Summary:
The powers of Congress begin and end with the Constitution. The Constitution vests Congress with explicit authority to enact criminal laws relating to counterfeiting, piracy, crimes on the high seas, offenses against the law of nations, and treason. It grants Congress other broad powers, such as the power to regulate interstate commerce. The Constitution's Necessary and Proper Clause allows Congress to enact criminal laws when reasonably related to the regulation of commerce or to one of the other constitutionally enumerated powers. The Constitution also imposes limits on the powers of Congress, however. It places those limits in the terms it uses in its grants of authority, in explicit prohibitions, and in the Tenth Amendment reminder of the restrictions implicit in the federal union. Recently, the Supreme Court and the lower federal appellate courts have supplied several examples of the scope and limits of congressional authority.
In the case of the Commerce Clause, seven Justices of the Supreme Court endorsed separate opinions in National Federation explaining that the power to regulate interstate commerce does not include the power to require participation in commerce. The Fifth Circuit held in Kebodeaux that the Commerce Clause does not embody the power to outlaw purely intrastate movement with only an attenuated nexus to commercial activity. As for foreign commerce, the circuits disagree on whether Congress's regulatory authority is subject to the same constraints that apply to its powers over domestic commerce. The Ninth Circuit (Clark) believes it is not. The Third Circuit (Pendleton) disagrees. (The Violence Against Women Reauthorization Act, P.L. 113-4 (S. 47), eliminates the need to prove a foreign commerce element in the law that gave rise to the circuit split.)
In the realm of the Necessary and Proper Clause, the Eleventh Circuit in Belfast observed that Congress may pass criminal legislation in order to implement a treaty obligation, and the Third Circuit in Bond held that it may do so without regard to federalism concerns. Moreover, the Ninth Circuit Court of Appeals concluded in Elk Shoulder that Congress may outlaw the unregistered movement within a state of a federally convicted sex offender who is on supervised release. The Fifth Circuit held in Kebodeaux, however, that the Clause does not permit enactment of a statute that outlaws such movement after the offender has been fully discharged. Although they did not join in a single opinion, seven Justices in National Federation concluded that Congress's power under the Spending Clause may not be used to compel the states to accept expansion of a federal regulatory regime or to face draconian economic consequences. The case did not involve criminal penalties, but a limit on Congress's Spending Clause power is a limit on its authority to enact implementing necessary and proper criminal legislation.
Article I, Section 8, clause 10 grants Congress the power "to define and punish Piracies and Felonies committed on the high Seas, and Offenses against the Law of Nations." Federal appellate courts have looked to customary international law for explanations of the power over offenses against the law of nations (Bellaizac-Hurtado) and piracy (Dire). The High Seas cases (Saac and Ibarguen-Mosquera) continue to acknowledge congressional authority to outlaw drug trafficking in international waters subject only to an elusive due process limitation. The Constitution's Military Clauses permit Congress to criminalize overseas assaults by Defense Department foreign contractors (Brehm), but do not permit it to punish an individual's conduct based solely on his status as a former member of the Armed Forces even when supplemented by the Necessary and Proper Clause (Kebodeaux).