This essay first appeared in the June 4, 2021 Epoch Times.

Early in the Biden administration, the president tapped Vice President Kamala Harris as his “point person” to address illegal immigration at the southern border.

By all accounts, Harris is refusing to carry out the job.

When inaugurated, every president takes an oath to “preserve, protect, and defend the Constitution of the United States.” Similarly, the vice president swears “to support and defend the Constitution.” So it’s fair to consult the Constitution to assess these two officers’ performance.

Let’s begin with a very basic question: Does the Constitution give the federal government authority to regulate immigration?

You might think it would have to. Controlling borders is a basic element of sovereignty. Nations must do so to survive. When the Roman Empire—to cite a prominent historical example—lost control of its borders, it soon ceased to exist.

The Constitution’s enumerations (lists) of federal powers do not include the word “immigration” or “borders.” But the Constitution does feature a clause (Article I, Section 9, Clause 1) that creates an exception to a presumed federal power over immigration. It provides that before the year 1808, Congress could not forbid (1) importation of slaves or (2) immigration of free persons.

When you see an exception in a legal document, it tells you the document contains a general rule to which the exception applies. By way of illustration, the pre-1808 ban on laws prohibiting the slave trade was an exception to Congress’s power to “regulate Commerce … with foreign Nations.” (The slave trade was considered a particularly disgusting form of “Commerce.”)

But for years, commentators argued over the source, if any, of the federal government’s authority over voluntary immigration.

Some hypothesized that Congress received this authority from the Commerce Power. The defect in that hypothesis is that when the Constitution was written, the term “regulate Commerce” did not include (pdf) governance of land travel for non-mercantile purposes.

Others thought the federal government had unmentioned “inherent sovereign authority” to regulate immigration. But the explicit wording of the Tenth Amendment refutes this: It says the feds have no powers the Constitution doesn’t enumerate. Indeed, a principal reason for the Tenth Amendment was to forestall claims of “inherent sovereign authority.”

Finally, some libertarians and open-borders advocates denied that Congress had any general authority to regulate voluntary immigration at all. By this reasoning, the pre-1808 immigration exception must have been a mere drafting error—an exception without anything to except to. As I observed in a previous essay, however, the Constitution’s framers were deft and highly experienced legal draftsmen, not prone to such rookie mistakes.

As often happens, all this uncertainty arose from modern ignorance of 18th-century law.

Several years ago I investigated whether the Constitution granted the federal government control over immigration. The answer was easy to find: It was in law books well known to the Constitution’s framers, and sometimes mentioned by participants in the constitutional debates of 1787–1790. I reported my findings in a book for the lay market and in weblog essays for legal scholars. Here’s what I learned:

The Constitution gives Congress power to regulate immigration in the document’s Define and Punish Clause (Article I, Section 8, Clause 10). The relevant words are—

“The Congress shall have Power … To define and punish … Offenses against the Law of Nations.”

“The Law of Nations” was the usual 18th century term for international law. Border control was part of the law of nations. For example, if one country allowed its people to cross the border into an unwilling country, that violated the law of nations. The same body of law specifically empowered individual countries to decide who could immigrate or emigrate, and under what conditions.

Thus, by empowering Congress “to define and punish … Offenses against the Law of Nations,” the Constitution gave Congress the ability to enact statutes regulating immigration. Of course, Congress has done exactly that.

Next question: If President Joe Biden deems an immigration law unwise, may he refuse to enforce it? The constitutional answer is “Absolutely not!”

Long before the American Founding, some English kings tried to assert the prerogative of “suspending” duly-enacted laws. The English rejected this claim in their Bill of Rights (1689). Our Founders anticipated that a rogue president might make the same claim. So Americans rejected it in the Constitution.

The Constitution provides that the president “shall take Care that the Laws be faithfully executed” (Article II, Section 3). The “take Care” phrase comes from 17th- and 18th-century legal documents that command agents to perform certain actions.

In other words, the Constitution tells us that President Biden—and Vice President Harris, if given authority—must enforce the immigration laws. Certainly they have some prosecutorial discretion. But if they fail to take strong action to secure the borders, they flout both the Constitution and their oaths of office.

Another part of the document reinforces that message. The Constitution’s Guarantee Clause (Article IV, Section 4) says in part:

“The United States shall guarantee to every State in this Union a Republican Form of Government, and shall protect each of them against Invasion …”

In this provision, “The United States” means the U.S. government. The Guarantee Clause requires the government—necessarily including the president as chief executive officer—to protect all states against “Invasion.”

Like the Take Care Clause, this is a mandate, not an option.

What is an “Invasion?” The term does not include disorganized civilians sneaking across the border, acting on their own and for their own reasons. Calling that an “invasion” would be silly—as silly as calling an unorganized, unarmed incursion into the U.S. Capitol an “insurrection.”

However, much illegal immigration over the southern border consists of caravans and third-party human smuggling. That activity is well planned and well financed. Whether it qualifies as an invasion under the modern use of the word is a matter for argument. But there can be no doubt that it qualifies as an “Invasion” as the Constitution uses the word.

Dictionaries in circulation during the 18th century defined “invasion” in ways that clearly include caravans and organized trans-border human smuggling. For example, a dictionary published just four years before the Constitution was written defined “invasion” as “a descent upon a country, an [sic] usurpation, or encroachment.”

In summary:

• The Constitution empowers Congress to pass laws regulating immigration.
• Congress has done so.
• The Constitution’s Take Care Clause requires the president—and his agents, including the vice president if the president gives her authority—to enforce those laws.
• In addition, the Constitution’s Guarantee Clause requires the president to guard the country from significant organized illegal border crossing; and
• Any president (or vice president, if authorized) who fails to carry out these responsibilities is violating the Constitution and his or her solemn oaths of office.