Emer de Vattel’s “Law of Nations,” a leading 18th century treatise on the subject.

The text of the Constitution strikingly does not explicitly give Congress any general authority to enact immigration restrictions. Conventional efforts to find that authority in the Naturalization Clause, the Commerce Clause, and supposedly “inherent” powers of sovereignty run into serious problems. Nor is such authority implied by the the Migration or Importation Clause.

In a recent op ed in The Hill, legal scholar Rob Natelson argues that federal power over immigration can instead be derived from Congress’ power to “define and punish . . . Offenses against the Law of Nations”:

“The law of nations” was the usual 18th-century term for international law. It included standards of conduct among nations. But it also encompassed some rules within national boundaries. A power to “define and punish” an “offense against the law of nations” included protecting foreign ambassadors against interference, protecting safe-conduct passes — and restricting immigration.

Why have so many writers — including some constitutional law professors — missed this? One reason is that 18th-century legal terms and categories were different from those we use today. For example, a modern law book might feature a heading for “immigration law.” But in William Blackstone’s “Commentaries,” the English book that served as America’s most popular legal treatise, there was no such heading.

Instead, Blackstone addressed the topic in his chapter on the British king’s prerogative powers. When discussing safe-conduct passes, Blackstone observed that without them “by the law of nations no member of one society has a right to intrude into another … [I]t is left in the power of all states, to take such measures about the admission of strangers, as they deem convenient.”

The law of nations argument is creative. But it ultimately fares no better than more conventional rationales for a general federal power over immigration.

Eighteenth century understandings of the law of nations did indeed assume that each state has the authority to restrict the entry of aliens, largely as it sees fit. But the fact that international law recognized the exclusion of aliens as a power of sovereign states does not mean that a violation of a national law restricting migration is thereby a violation of the law of nations. Blackstone and the other eighteenth century writers cited by Natelson make the former claim, but not the latter.

In the eighteenth century, and even today, international law recognizes exclusive state authority to make laws on a wide variety of subjects. That does not mean that any violation of national laws on those issues becomes a violation of international law. For example, states generally have exclusive authority over domestic violent crime. Yet that does not make every act of rape and murder a violation of international law, even if committed by an alien on the state’s territory. If an American commits a violent crime on Mexican soil or vice versa, there is no violation of international law. The same point applies to border crossing by peaceful migrants. It too sometimes violates national law, but does not thereby violate any international law. Congress’ power to punish offenses against the law of nations is a power to punish acts that themselves violate international law, not a power to regulate any activity whose control international law leaves to the discretion of individual nations. Otherwise, Congress would have the power to ban virtually any activity that a state government could forbid. After all, nearly all the latter also are issues left to the discretion of individual states under 18th century international law. That, of course, would destroy any meaningful constitutional limits on federal power..

Natelson quotes Emmer de Vattel, a prominent 18th century authority on international law, who wrote that in “Switzerland and the neighboring countries … the law of nations … did not permit a state to receive the subjects of another state into the number of its citizens.” Significantly, however, this passage does not address migration, but grants of citizenship. And it does not claim that the receiving state has an international law right to exclude migrant, but rather that the sending state has a right to prevent its subjects from pledging their allegiance to a foreign power. The claim here is that rulers have a monopoly over their subjects’ allegiance, which the latter are forbidden to change without the ruler’s consent. This was disputable even in the 18th century. Many states, including Great Britain took in refugees from other nations (e.g. – Huguenot Protestants fleeing persecution in France) and granted them citizenship without the consent of their original rulers. Vattel himself wrote that this was not a general principle of international law, but rather a “vicious custom [that] had no other foundation than the slavery to which the people [of that area] were then reduced. A prince, a lord, ranked his subjects under the head of his private property: he calculated their number, as he did that of his flocks; and, to the disgrace of human nature, this strange abuse is not yet every where eradicated.”

The idea of an international law right of rulers to keep their subjects from becoming citizens of other states is even more dubious today, when international human rights law explicitly recognizes a right of emigration, which undercuts the previously traditional notion of a sovereign’s monopoly power over its citizens. In any event, here as elsewhere, power over grants of citizenship is separable from power over migration.

A slightly different variant of the law of nations argument is that the Define and Punish Clause gives Congress the power to forbid any acts that a foreign nation has an international law obligation to prevent, such as the use of its territory to launch attacks against a neighbor. But in the eighteenth century, and even today, states have no international law obligation to prevent the peaceful migration of their citizens to foreign nations that might wish to exclude them. For example, no serious commentator contends that Mexico’s failure to prevent migration by its citizens to the United States is a breach of its international law obligations, even if the migrants violate US immigration law.

Finally, one could argue that the Define and Punish Clause gives Congress broad power to define almost anything it wants as an offense against the law of nations. But such a power would undermine the overall scheme of enumerated powers and make many of Congress’ other listed powers superfluous.

For the moment, the relationship between the Define and Punish Clause and immigration law has only limited real-world significance. Since the Chinese Exclusion Cases of the 1880s, the Supreme Court has held that Congress has inherent power to restrict migration, despite the fact that it cannot be found in any specific provision of the Constitution. Living constitutionalists can embrace this theory (whose origins were heavily influenced by late-19th century racism and xenophobia) without much concern about whether it fits the text or the original meaning of the Constitution. But the lack of any textual basis for congressional power over immigration should bother originalists and textualists. In time, it might help lead courts to pare back the pernicious “plenary power” doctrine, which holds not only that Congress has virtually unlimited authority over immigration, but that it is not even subject to most of the individual rights constraints that restrict other exercises of federal power.

NOTE: Some of the material in this post is adapted from an academic article I am working on, about federal power over immigration.

UPDATE: A post at the Hot Air blog responds to this post, but does not seriously engage with the argument about the law of nations. Instead, it makes the absurd claim that my position would prevent the federal government from keeping out invading armies. Pretty obviously, invading armies are not migrants, and Congress’ and the President’s power to wage war give them authority to block their entry. Peaceful migrants are a different matter.
Most of the rest of the post is taken up with claiming that the Migration or Importation Clause implies a general federal power over migration. I addressed such claims in detail here, and I think fair-minded readers will see that the Hot Air blog has failed to meaningfully counter the extensive evidence against that position.

UPDATE #2: Rob Natelson responds to this post here. I am glad to see that we agree in rejecting the more traditional (and more widely believed) constitutional justifications for a general federal power over immigration.

On the issue of the law of nations, Natelson’s thoughtful post cites a variety of passages from various 18th century writers. But, as he anticipates, I can deal with them by simply pointing out that they, like the ones already discussed above, merely show that the 18th century law of nations left immigration policy to individual sovereigns, not that violations of national immigration laws amount to violations of international law. For most of the passages he cites, this is pretty obviously true.

A couple, however, are more ambiguous. For example, he quotes Blackstone as writing that “by the law of nations no member of one society has a right to intrude into another.” But this does not claim that the law of nations forbids such “intrusion,” merely that it does not affirmatively grant a right to engage in it. The full passage in which this sentence occurs clearly indicates that Blackstone intended merely to indicate the absence of an affirmative right: “Upon exactly the same reason [as the granting of letters of marque and reprisal to privateers] stands the prerogative of granting safe-conducts, without which by the law of nations no member of one society has a right to intrude into another.” Blackstone was merely indicating that the grant of a “safe-conduct” creates an international law right where none existed before.

Natelson quotes Vattel to the effect that “We should not only refrain from usurping the territory of others; we should also respect it, and abstain from every act contrary to the rights of the sovereign: for a foreign nation can claim no right in it.” But nowhere does Vattel claim that these principles are mandated by international law, as opposed to morality or prudence. To the contrary, both in the 18th century and today, people often engaged in “acts contrary” to the “rights” of sovereigns that were not considered violations of international law.

He also quotes Vattel’s statement that “[f]inally, there is another case where the nation in general is guilty of the crimes of its members. That is when by its manners and by the maxims of its government it accustoms and authorizes its citizens . . . to make inroads into neighboring countries.” Similarly, he quotes Vattel’s statement that “If a sovereign, who might keep his subjects within the rules of justice and peace, suffers them to injure a foreign nation either in its body or its members, he does no less injury to that nation, than if he injured it himself.” I think theses passages refer to direct encouragement and support of illegal activity by the government, rather than merely failing to prevent individual citizens from engaging in it. In the same passage as the second quote noted by Natelson, Vattel emphasizes that “[w]e ought not then to say in general, that we have received an injury from a nation, because we have received it from one of its members.” At least as a general rule, he concludes we should only do so if ” if a nation or its chief approves and ratifies the act of the individual.”

Even if Vattel meant the broader view, it certainly was not the case that 18th century international law was generally understood as holding sovereigns responsible for every incident where one of their subjects entered another nation in violation of its laws. Such a rule would have made every unauthorized border crossing a potential international crisis.

Natelson continues to rely on Vattel’s quote about granting citizenship to foreigners (discussed above). I stand on the arguments already made on this score. In particular, Natelson has no answer to the point that Vattel did not claim that this was general principle of the law of nations, but merely a custom adhered to by Swiss rulers, and possibly some of their neighbors (one Vattel considered to be outdated by his time).

Finally, I would add this last point: Both 18th century writers and modern ones recognize that the content of international law can change over time. For example, 18th century international law allowed sovereigns to ban emigration, as well as immigration, but today the former is forbidden by international human rights law. Even if unauthorized border crossing was considered a violation of the law of nations then, it certainly is not today. The Define and Punish Clause does not give Congress the power to forbid anything that might have been banned by the law of nations at some time in the past, but merely that which actually is illegal under it today. Otherwise, we end up with the absurd result that the Clause would authorize Congress to ban activities that are perfectly legal under the law of nations as it now exists, or even actually required by it.