Whether the federal government has the power to regulate immigration is an exceptionally important question. In City of Richmond v. J.A. Croson Co., Justice Scalia proposed that “racial discrimination against any group finds a more ready expression at the state and local than at the federal level”; if true, immigration policy is the glaring exception. Throughout American history, immigration law has been the location of perhaps the most egregious forms of discrimination by the federal government. From racial restrictions on naturalization in effect from 1790 to 1952, to laws excluding immigrants on the basis of race, gender, religion, political beliefs, and sexual orientation, to extra-judicial expulsion of U.S. citizens and others on the basis of race, U.S. immigration policy has often been inhumane and dishonorable. I am among those who believe that contemporary immigration policy remains driven by invidious considerations.
But there is no Brown v. Board of Education of immigration law, breaking with the past and announcing a new jurisprudence. Instead, to a significant degree, discrimination has been tolerated by courts based on the shifting, inconsistent, and vague explanations of executive and congressional power Professor Somin described. The courts have said that “Over no conceivable subject is the legislative power of Congress more complete than it is over the admission of aliens,” and therefore that “in the exercise of its broad power over immigration and naturalization, Congress regularly makes rules that would be unacceptable if applied to citizens.”
Notwithstanding its recognition of the federal government’s limited powers, the Supreme Court has made no rigorous, consistent effort to explain precisely where immigration authority comes from or how far it extends. Professor Somin is absolutely right that once that power—if any—is identified, it will become necessary to determine the extent to which that power is subject to the Bill of Rights and other constitutional restraint, and therefore which provisions of the Immigration and Nationality Act are unconstitutional.
Professor Somin also persuasively argues that the most promising source of textual authority, the Migration Clause, is insufficient. The unavoidable historical context is that this was a disguised reference to the slave trade, not to immigration in general. In addition, there is little question that the form of human trafficking practiced at the time, odious as it was, constituted commerce subject to federal regulation. If voluntary immigration also constitutes commerce, this clause becomes unnecessary to give Congress power to regulate it. If on the other hand voluntary immigration does not constitute commerce, then this clause, which, again, deals with commerce, might well be inapposite.
The question in my mind becomes whether the congressional power to “regulate Commerce with foreign Nations, and among the several States, and with the Indian tribes” authorizes regulation of immigration. My tentative answer is that a Commerce Clause justification has not yet been disproven. Professor Somin points out that the Clause
merely gave Congress the power to restrict interstate trade and other commercial transactions, not to forbid movement as such. The Commerce Clause also gives Congress the power to regulate interstate as well as international commerce. The Constitution literally uses the same phrase to cover both, giving Congress the power to “regulate Commerce with foreign Nations, and among the several States.” Yet few if any eighteenth and nineteenth century jurists would have argued that Congress therefore had the power to forbid Americans from moving from one state to another.
First, a practical problem. If immigration is not federally regulated, it is either subject to state regulation, which implies border checkpoints for all (as, say, Arizona exercises its right to keep out immigrants that California has decided to admit) or no regulation whatsoever, an eyebrow-raising prospect.
More fundamentally, the law offers a way out of the dilemma: “Commerce” definitionally might include migration across the border of a state or of the United States, but U.S. citizens might have the right to cross state borders without federal (or state) restriction based on other provisions of the Constitution. Although Chief Justice Roger Taney is best remembered for being wrong, he was correct when he wrote that every citizen of the United States, “from the most remote States or Territories” is entitled to access to federal courts and offices in every state,
And the various provisions in the Constitution of the United States—such, for example, as the right to sue in a federal court sitting in another State, the right to pursue and reclaim one who has escaped from service, the equal privileges and immunities secured to citizens of other States, and the provision that vessels bound to or from one State to another shall not be obliged to enter and clear or pay duties—all prove that it intended to secure the freest intercourse between the citizens of the different States.
Of course, rights granted by the Constitution to citizens are not necessarily enjoyed by noncitizens; that citizens may travel freely between the states does not mean that unnaturalized immigrants also have that liberty in the face of a federal prohibition.
The ultimate issue is whether immigration is commerce. I do not claim comprehensive knowledge of the historical sources. However, venerable precedents certainly leave room for treatment of immigration as commerce. In Gibbons v. Ogden, an 1824 case, Chief Justice Marshall for a majority determined that the business of transportation of passengers by vessel was commerce. It would be drawing a very fine line to hold that the federal government can regulate the business of transporting noncitizens by, say, imposing a $100,000 head tax, but not go so far as to forbid the actual entry of noncitizens.
In 1837, Justice Barbour for the Court held that New York could require ship masters to file passenger lists with local authorities, the Commerce Clause notwithstanding. Precedents limiting state regulation of interstate goods were inapplicable because “the goods are the subject of commerce, the persons are not.” But in 1849, when the question was the power of states to tax immigrants from other countries, the Court, 5-4, concluded regulation of immigrants as such was commerce reserved to the national government. Asking for information was one thing; taxing, which could result in exclusion, was another matter.
In sum, I would like to hear more from Professor Somin about why the Commerce Clause is an insufficient basis for federal regulation, and why specification of the Commerce Clause as the main source would be an insufficient foundation for beginning the project of subjecting federal immigration authority to ordinary constitutional limitation.
 See Gibbons v. Ogden, 22 U.S. 1, 206-07 (1824) (Marshall C.J.) (reserved state right in the Migration Clause “constitutes an exception to the power of Congress to regulate commerce”); id. at 216-17. But see Smith v. Turner, 48 U.S. 283, 453 (1849) (McKinley J., concurring) (arguing that Migration Clause applies both to slaves and other classes of migrants).
 Smith v. Turner, 48 U.S. 283, 492 (1849) (Taney C.J., dissenting). Similarly, Professor Barnett identifies several constitutional provisions which “deny Congress the same degree of regulatory power over domestic commerce that it has over commerce with foreign nations.” Randy E. Barnett, The Original Meaning of the Commerce Clause, 68 U. Chi. L. Rev. 101, 144 (2001).
 Cf. Nancy Morawetz, The Invisible Border: Restrictions on Short-Term Travel by Noncitizens, 21 Geo. Immigr. L.J. 201, 205 (2007) (“Restrictions on travel exist for noncitizens across situation and status.”)
 Gibbons v. Ogden, 22 U.S. 1, 215-16 (1824) (Marshall C.J.) (“A coasting vessel employed in the transportation of passengers, is as much a portion of the American marine, as one employed in the transportation of a cargo; and no reason is perceived why such vessel should be withdrawn from the regulating power of that government, which has been thought best fitted for the purpose generally.”)
 City of New York v. Miln, 36 U.S. 102, 136 (1837).
 There were eight opinions. Justice Wayne’s concurring opinion proposed:
I think the court means now to decide,—
1. That the acts of New York and Massachusetts imposing a tax upon passengers, either foreigners or citizens, coming into the ports in those States, either in foreign vessels or vessels of the United States, from foreign nations or from ports in the United States, are unconstitutional and void, being in their nature regulations of commerce contrary to the grant in the Constitution to Congress of the power to regulate commerce with foreign nations and among the several States.
Smith v. Turner, 48 U.S. 283, 412 (1849) (Wayne J., concurring).