Whatever federal politicians may feel about immigration policy or the migrant caravan, their constitutional duty is clear: They must prevent the caravan from entering the United States by whatever means necessary.
The caravan consists of 90-95 percent men, not the women and children featured in the mainstream media. The organizers’ strategy apparently is the same as that employed by Germanic migrants into the later Roman Empire — to overwhelm the border by force of numbers.
Like caravan participants today, the migrants forcing their way across the Roman borders had varying reasons for their behavior. Some merely wanted a better life. Others harbored more sinister motives. But whatever the individual reasons, the result was destruction of the western Roman state.
Many of the American Founders were students of Roman history. That may have contributed to their decision to insert the Guarantee Clause (Article IV, Section 4) into the Constitution. The Guarantee Clause provides that “The United States shall guarantee to every State in this Union a Republican Form of Government, and shall protect each of them against Invasion; and on Application of the [state] Legislature, or of the Executive (when the Legislature cannot be convened) against domestic Violence.”
We can argue about whether the caravan is an “invasion” as we use the word today. But sources contemporaneous with the Constitution tell us what the Founders meant by the term. Nathan Bailey’s 1783 English dictionary defined “invasion” as “a descent upon a country, an [sic] usurpation, or encroachment.” Similarly, Thomas Sheridan’s 1789 dictionary and the 1785 edition of Samuel Johnson’s dictionary defined “invasion” as “Hostile entrance upon the rights or possessions of another, hostile encroachments.”
These and other lexicographers agreed that an “invasion” did not have to be military in nature or be comprised of active-duty soldiers.
In other words, the caravan is an “invasion” within the meaning of the Constitution’s Guarantee Clause.
Moreover, that clause does not merely empower federal officials to repel an “invasion.” It commands them to do so. And unlike the case of domestic violence, the federal duty to repel an “invasion” is immediate and unconditional.
In one respect the Guarantee Clause is unique in the Constitution. Many other provisions grant power or impose obligations on specific branches or officers — that is, on Congress or on the courts or on federal or state officials. But the Guarantee Clause, by contrast, imposes obligations on “the United States.” It is directed to all officers and divisions of the federal government. Because of the way the Constitution uses language, the Guarantee Clause may even bind state and local officials.
As practical matter, of course, the obligation of first response falls on the president. The Constitution specifies that “The President shall be Commander in Chief of the Army and Navy of the United States … He … shall take Care that the Laws be faithfully executed.”
The president’s duty to repel invasion — like the duty of other officials — is absolute. It is not optional or conditional. The president takes a specific oath to “faithfully execute the Office of President of the United States, and … preserve, protect and defend the Constitution of the United States.”
But while the obligation of first response lies with the president, this does not let Congress off the hook. As the general legislature of “the United States,” Congress also has a constitutional obligation to work to repel an “invasion.” Congress must appropriate required funds. It must enact necessary laws. It must not drag its feet or obstruct defense efforts. To the extent congressional measures are efforts to stall or impede response against an invasion, those measures violate the Guarantee Clause. They are unconstitutional. The same is true of obstructive actions by other federal officials and may be true of obstructive efforts by state and local officials.
We can debate and negotiate immigration policy, including the reasons behind the caravan. But the Constitution is clear: Protecting the border comes first, and that obligation is unconditional, undebatable, and non-negotiable.
Robert G. Natelson was a law professor for 25 years teaching constitutional law, constitutional history and related courses. He is currently senior fellow in Constitutional Jurisprudence at the Independence Institute in Denver. He has published extensively on the Constitution, including the Guarantee Clause, and is the author of The Original Constitution: What It Actually Said and Meant.