Republican politicians have embraced immigration as a potent political issue. In addition to making conventional arguments that the Biden administration’s border policies are bad and should move voters in the upcoming election to reject both President Joe Biden and Democrats generally, certain Republican state officials and members of Congress have taken to characterizing the increased flow of undocumented migrants as an “invasion” and to claiming that administration policies violate Article IV of the U.S. Constitution which provides that, “The United States shall … protect each [state] against invasion.”

Texas Governor Greg Abbot has used this “invasion” claim to justify open defiance of federal supremacy over control of the national border. And some Republicans pushing impeachment of Homeland Security Secretary Alejandro Mayorkas have alleged that he violated the Constitution by failing to protect the states against the supposed immigrant “invasion” (although the most recent iteration of proposed articles of impeachment against Mayorkas does not rely on the constitutional “invasion” claim, instead claiming that Mayorkas “refused to comply” with federal immigration law, among other arguments).

The causes of and solutions for the current migration surge are fairly debatable. However, the claim that a large increase in the number of would-be migrants gaining entry at the southern border constitutes an “invasion” under Article IV is constitutional nonsense. It cannot be sustained by any reasonable reading of the text of the Constitution, the original understanding of the Constitution, or subsequent interpretations of the Constitution by courts or constitutional scholars.

“Invasion,” Insurrection, and Other Violent Threats at the Time of the U.S. Founding

Both the 1777 Articles of Confederation and the U.S. Constitution, composed ten years later, were not only frameworks of civil government but also, and critically, set out the terms of a military alliance between previously sovereign states confronted by external (and occasionally internal) military threats.

In 1777, the colonies which had the previous year declared themselves “Free and Independent States,” were perilously engaged in a shooting war against their former colonial overlord, Great Britain. Although by the time of the Philadelphia Constitutional Convention of 1787 independence had technically been won, the new United States were surrounded by territory occupied or claimed by acquisitive European imperial powers – British Canada on the north and Spain’s vast possessions to the south and west, with the French threatening reassertion of their prior claims to Louisiana and the Mississippi Valley. Moreover, U.S. coastwise and trans-Atlantic sea trade was vulnerable to vastly larger European navies. In addition, the newly independent states and their outlying western settlements warred intermittently with Native American tribes justifiably hostile to increasing European encroachment into their tribal territories.

The founding generation was also worried about two other kinds of military threat – armed insurrection against state governments from within or, strange though it may seem to us now, invasions of one state by another state or confederation of states. Accordingly, they wanted to ensure that the military resources of the entire union could be employed to suppress local insurrection or interstate aggression.

At the Constitutional Convention, multiple Framers repeatedly expressed the view that the Articles of Confederation required replacement because they provided the national government insufficient powers to defend the nation or individual states militarily against “foreign invasion” or domestic insurrections.

For example, at the outset of the Convention, Virginia Governor Edmund Randolph criticized the so-called New Jersey Plan for a new constitution by maintaining that its strong legislature and weak executive would yield military weakness. He said:

Originally, our Confederation was founded on the weakness of each state to repel a foreign enemy; and we have found that the powers granted to Congress are insufficient. The body of Congress is ineffectual to carry the great objects of safety and protection into execution. What would their powers be over the commander of the military, but for the virtue of the commander? . . . [Congress are] too numerous for an executive; nor can any additional powers be sufficient to enable them to protect us against foreign invasion. (emphasis added).

Randolph immediately went on to observe that, “Congress was intended to be a body to preserve peace among the states; and, in the rebellion of Massachusetts [Shay’s Rebellion of 1786-87], it was found that they were not authorized to use the troops of the Confederation to quell it.”

Later in the Convention, Massachusetts delegate Rufus King observed of the constitution under construction: “What are the great objects of the Genl. System? 1. difence agst. foreign invasion. 2. agst. internal sedition.” (emphasis added).

Throughout the Constitutional Convention and the state ratification debates that followed, delegates and commentators used the term “invasion” over and over. With a handful of exceptions where “invasion” is used metaphorically, as when referring to an “invasion of rights,” the word invariably refers to a hostile armed incursion into or against the territory of the states or the nation, an incursion that must be met with a military response.

For example, at the Convention, Alexander Hamilton disparaged continental examples of loose federal systems by saying:

Let us examine the federal institution of Germany. It was instituted upon the laudable principle of securing the independency of the several states of which it was composed, and to protect them against foreign invasion. Has it answered these good intentions? Do we not see that their councils are weak and distracted, and that it cannot prevent the wars and confusions which the respective electors carry on against each other? (emphasis added).

The Framers’ fundamental objective of creating a national government strong enough to repel foreign military incursions and armed domestic insurrections is manifest in the clauses that speak of “invasion” in the Constitution they drafted.

Uses of “Invasion” in the Text of the Constitution

The word “invasion” or “invaded” appears in four clauses of the U.S. Constitution, all of which relate to the military alliance aspect of the Constitution, or what we might now call its national security architecture. Whether considered individually or collectively, these four usages plainly refer to a hostile armed incursion into or against U.S. territory. Indeed, they cannot reasonably be understood any other way.

Article IV, Sec. 4:

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 Legislature, or of the Executive (when the Legislature cannot be convened) against domestic Violence.

Article IV contains the basic security guarantee that provided a primary inducement for the states to join in a constitutional union with strong national powers – the guarantee of mutual defense against both “invasion” from without, and upon special request, against “domestic violence,” i.e., insurrection or violent civil disturbances, from within.

In Madison’s discussion of Article IV in Federalist 44, he emphasizes that states require “protection against invasion” by both “foreign hostility” and potentially even aggressive fellow states of the union. Throughout Federalist 44, he speaks of both invasion and insurrectionary “domestic violence” as “bloody” events involving “military talents and experience” and “an appeal to the sword.”

Article I, Sec. 8:

The Congress shall have Power … To provide for calling forth the Militia to execute the Laws of the Union, suppress Insurrections and repel Invasions.

This clause prescribes the mode of military organization that the Founders – who opposed the maintenance of a national standing army – imagined would be employed to defend the nation and individual states against internal insurrections and foreign invasions: the power of the congress to call state militias into national service. Although the militia system has long since been superseded by a huge standing army (and navy and air force), not to speak of a vast military-industrial apparatus, that does not change the plain meaning of “invasions” in this clause – hostile armed incursions into or against U.S. territory that must be repelled with military force.

Article I, Section 10, cl. 3:

No State shall, without the Consent of Congress, lay any Duty of Tonnage, keep Troops, or Ships of War in time of Peace, enter into any Agreement or Compact with another State, or with a foreign Power, or engage in War, unless actually invaded, or in such imminent Danger as will not admit of delay.

Section 10 of Article I reserves to the national government exclusively the conduct of foreign policy. It also prohibits states from maintaining regular armies and navies in time of peace, and absolutely bars them from “engag[ing] in War, unless actually invaded, or in such imminent danger as will not admit of delay.”

In other words, the constitutional response to “invasion” is “war.” Section 10, when read together with the provision of Article I, Section 8, that grants Congress the power “to declare war,” confers the responsibility for national defense – for making war – on the national government. The Constitution leaves only one narrow exception for emergencies in which states can “engage in War” if they are “actually invaded” or under imminent threat of invasion or a “Danger” so great that it would merit war in response. Even then, the plain implication of the opening requirement of consent of Congress together with the concluding exception for dangers that “will not admit of delay” is that even a state “actually invaded” cannot make war on its own indefinitely, but must appeal to Congress as soon as possible for its consent and support.

Article I, Sec. 9, cl. 2:

The Privilege of the Writ of Habeas Corpus shall not be suspended, unless when in Cases of Rebellion or Invasion the public Safety may require it.

Article I, Section 9, concerns the basic Anglo-American right of habeas corpus – that is, the right to demand that a court determine whether there is a legal basis for criminal arrest and detention of every person. Section 9 decrees that this right can only be suspended in cases of “Rebellion or Invasion.” This special exception for rebellion and invasion recognizes that in times of actual armed conflict, normal legal protections may have to be suspended.

Post-Convention Discussion of “Invasion” as Used in the Constitution

In the Virginia ratifying convention, James Madison responded to criticism of the Constitution’s grant to the national government of the power to call state militia into national service by saying:

If insurrections should arise, or invasions should take place, the people ought unquestionably to be employed to suppress and repel them, rather than a standing army. The best way to do these things, was to put the militia on a good and sure footing. (Emphasis added).

Madison quite naturally thinks of invasions as well as insurrections as military events requiring an armed military response. Similarly, when Luther Martin, a delegate to the federal convention, later wrote of his concerns about the draft constitution to the Maryland convention, he noted that the power to “suppress insurrections and repel invasions” necessarily involves “calling forth the militia” and thus subjecting Maryland citizens “to military law.”

The Rhode Island convention ratified the constitution, with the proviso that its delegates to the first Congress should propose a series of amendments, the sixth of which provided, “That no person shall be compelled to do military duty otherwise than by voluntary enlistment, except in cases of general invasion.” (Emphasis added).

At no point in the Constitutional Convention or any of the state ratification debates does anyone, except when speaking metaphorically, employ “invasion” to describe a non-violent, non-military event. (For an excellent survey of the customary usages of “invasion” or “invade” during the founding era, supporting the conclusion that “invasion” meant “physical ingress into a state (entry) and the intent by the invader to act as an enemy to that state (enmity),” see this reportby Joshua Treviño of the conservative Texas Policy Foundation.)

More to the present point, absolutely no one at the Constitutional Convention or the state ratification debates used the word to connote the peaceful movement of immigrants (lawful or otherwise) from one country to another.

Post Founding-era debates on uses of “invasion” in the Constitution

“Invasion” in Article IV: Curiously, the question of whether an influx of migrants could count as an “invasion” actually arose within a decade of the ratification of the Constitution. In 1798, the Federalists in control of Congress passed the now-infamous set of statutes we know as the “Alien and Sedition Acts.” One of these, known colloquially as the “Alien Friends Act,” gave the President unilateral authority to expel any alien “he shall judge dangerous to the peace and safety of the United States.” Supporters of this legislation claimed that it was authorized by Article IV’s invasion clause. But, as law professor Ilya Somin has pointed out in a series of excellent posts rebutting the contention that peaceful immigration can be termed a constitutional “invasion,” James Madison rejected such claims in his Report of 1800, declaring unequivocally: “Invasion is an operation of war. To protect against invasion is an exercise of the power of war.”

“Invasion” in the Suspension Clause: There has been an immense amount of debate about the precise scope of the Suspension Clause. For example, does it implicitly create a right of habeas corpus independent of any statutory enactment? And whatever may be the scope of the right, who possesses the suspension power, Congress or the President? But there is no doubt that the suspension power is triggered only “in Cases of Rebellion or Invasion.”

As law professor Neal Katyal and then-judge-now-Justice Amy Coney Barrett noted in their article on the Suspension Clause:

The writ of habeas corpus has been suspended four times since the Constitution was ratified: throughout the entire country during the Civil War; in eleven South Carolina counties overrun by the Ku Klux Klan during Reconstruction; in two provinces of the Philippines during a 1905 insurrection; and in Hawaii after the bombing of Pearl Harbor.

Three of these suspensions responded to armed internal rebellions. Lincoln’s suspension of the writ during the Civil War is well known. The Reconstruction incident is not, but it illustrates perfectly how the Suspension Clause is restricted to armed violence. In response to rise of the KKK in the formerly Confederate south and its campaign of organized violence against Black freedmen and white Unionists, including assaults, intimidation, and murder, Congress passed a series of laws, including the Third Force Act of 1871 authorizing President Grant to suspend habeas corpus. Particularly violent outbreaks in South Carolina led Grant on Oct. 17, 1871, to declare eleven counties in “rebellion” against the United States.

The third historical suspension of habeas corpus was prompted by the rebellion and three-year guerrilla war conducted by Filipinos against U.S. rule of what was then, by treaty with Spain, a U.S. possession.

The fourth suspension resulted from a devastating military strike by a foreign power on a U.S. territory, one that led to an immediate formal declaration of war against Japan.

In sum, over two centuries of precedent demonstrate that suspension of habeas corpus is constitutionally authorized only in response to organized, armed violence, whether a “rebellion” from within or an “invasion” from without. Thus, the word “invasion” as used in the Suspension Clause has the same meaning as in Article IV – it refers to a hostile armed incursion into or against the territory of the United States.

Court Decisions on the Meaning of “Invasion”

The courts have rarely addressed the meaning of “invasion” for constitutional purposes. However, the few decisions we have affirm that a large influx of legal or illegal aliens into a state does not constitute an “invasion” under Article IV and that the term invasion connotes armed hostility or military invasion.

In the 1990s, multiple states raised Article IV invasion claims, primarily for the purpose of compelling the federal government to reduce immigrant flows or provide additional funds to states to pay for the strain on state resources caused by large numbers of migrants. The uniform response of the courts was to find that such claims present a non-justiciable political question, see e.g., the Eleventh Circuit’s decision in Chiles v. United States.

But at least three courts went further to hold in the alternative that, as the Second Circuit put it in Padavan v. United States, “In order for a state to be afforded the protections of the Invasion Clause, it must be exposed to armed hostility from another political entity, such as another state or foreign country that is intending to overthrow the state’s government.” See also, the Ninth Circuit’s opinion in California v. United States (“California ignores the conclusion set forth by our Founders. In The Federalist No. 43, James Madison referred to the Invasion Clause as affording protection in situations wherein a state is exposed to armed hostility from another political entity.”); and the Third Circuit’s decision in New Jersey v. United States (New Jersey “offers no support whatsoever for application of the Invasion Clause to this case or for its reading of the term “invasion” to mean anything other than a military invasion”).

Non-Immigration Arguments for Existence of an “Invasion”

In an implicit concession that the mere passage into the country of a large number of peaceful immigrants cannot make a constitutional “invasion,” some Republicans have tried to base their claim on even more specious grounds. These include the contention that Biden administration immigration policy is the cause of the (genuinely alarming) rise of fentanyl abuse over the past few years, and that the administration has allowed drug cartels to gain “control of the border.”

I have addressed the obvious fallacy in the claim about fentanyl elsewhere. In a nutshell, it is ridiculous to assert that changes in policy regarding the admission of immigrants, whether by parole or otherwise, will materially affect the ability of foreign drug traffickers to import whatever quantities of a fungible, easily concealable, immensely profitable substance that the internal U.S. market demands. Aggressive interdiction did not, and does not, materially affect the domestic availability of cocaine, heroin, or methamphetamine. Nor can it have more than marginal effects on the availability of fentanyl.

Conversely, the claim that drug cartels “control the southern border” is mere sensationalist bombast. Do drug cartels succeed in importing large quantities of illegal drugs across U.S. borders? Yes. They have done so for decades. They will doubtless continue to do so as long as demand exists and profits can be made. Have drug smuggling operations also branched out into smuggling undocumented humans into the United States. Very possibly. But attributing human smuggling to “cartels” is to do no more than give a different, and darker sounding, name to “coyotes” who have long smuggled people from Mexico into the United States. But cartels do not “control” the border of the United States. No cartel mans official points of entry or the long spaces between. No cartel decides who and what is lawfully admitted into the country. Indeed, cartels are obliged to smuggle drugs (and some cases people) secretly precisely because they do not “control” the border.

At all events, an increase in the ever-fluctuating quantity of illegal drugs reaching the United States is not even arguably an “invasion” for constitutional purposes.

Searching desperately for some instance of physical penetration of U.S. territory by hostile, violent foreigners, some Republicans even claim that Biden immigration policy must be allowing “terrorists” into the county. Indeed, this is one of the claims in the current draft of the Mayorkas impeachment resolution. Their “evidence” is the fact that during the Biden administration, border authorities have encountered a larger number of persons listed on the “Terrorist Watch List” than was true during the Trump years. The fact that the dread watch list has now become so indiscriminate that it includes two million names goes unmentioned. As does the possibility that under Biden, border authorities are simply more vigilant that those under Trump. More importantly, Republicans cite no instance of an actual terrorist entering the country, still less a case of a terrorist who has slipped across the border and performed a terrorist act. As a justification for a declaration of a constitutional “invasion,” the “terrorist” canard is beneath serious consideration.

The Real Dangers in Declaring High Immigration Levels or Increased Drug Consumption an “Invasion”

Leaving aside the conclusive evidence from text, original understanding, historical precedent, and judicial interpretation that an “invasion” under Article IV requires a hostile armed incursion into or against the territory of the United States, as well as the complete absence of evidence that events at the southern border constitute such an invasion, perhaps the most compelling reason to reject Republican claims of invasion is the absurd, but deeply dangerous, practical implications that would flow from conceding the point.

First, as other commentators, including several of a notably conservative bent, have observed, if Texas is currently being “actually invaded,” then under Article I, Section 10, Texas can, at least arguably, “engage in war” to stop the “invasion.” What this would mean in practice is hard to foresee. But presumably it would permit the use of armed force against persons attempting to cross into the United States, and equally consequentially, a counter-invasion by Texas National Guard or police forces into Mexico to attack, with military weapons, anyone involved in facilitating illegal migration or any form of drug smuggling.

Even contemplating such events seems melodramatic, but multiple Republican politicians, including former President Trump, have publicly called for the use of the military inside Mexico to combat drug trafficking and human smuggling. While in past eras one could safely discount this kind of talk as mere self-aggrandizing bluster, it is not at all clear that a Republican governor like Texas’s Abbott (who is already blatantly challenging federal authority over the national border) might not sponsor some incursion to curry favor with the extreme right wing upon which he depends politically and thus increase his national profile. And should Trump be re-elected, a declaration of a supposed “invasion” from Mexico would provide an excuse to attack without congressional approval.

Second, and perhaps more terrifying, is the possibility that a declaration of “invasion” could be used to justify suspension of habeas corpus under Article I, Section 9. One can too easily imagine a re-elected and vengeful Trump citing the precedent of Abraham Lincoln to unilaterally suspend habeas for the duration of the immigrant / drug trafficker “invasion” of the United States. Because the supposed “invasion” would have no obvious geographic limit, the suspension could be employed to authorize a regime of warrantless and unreviewable detentions of anyone anywhere within the country suspected of being illegally present in the United States, anyone suspected of drug trafficking, and indeed anyone alleged to be aiding or even sympathizing with alien immigrants or drug sellers.

One certainly hopes, and anxiously assumes, that the Supreme Court would overturn such an effort to suspend habeas corpus. But the assumptions of a lifetime, and indeed of many lifetimes past, about what this Court might do, not to speak of whether a restored President Trump would abide by the Court’s orders if contrary to his whims, seem now very much in doubt.


The bottom line is that nothing now occurring at the U.S. southern border remotely amounts to an “invasion” as that term is used in any portion of the Constitution. However, the claim by a distressing number of Republicans in federal and state government that there is such an “invasion” is profoundly dangerous. Some Republicans in the House have used it to promote a grotesque misuse of the Constitution’s vital impeachment mechanism. Other Republicans are using it to justify actions by state governments that test the fabric of the Union.

For the sake of the country, this nonsense should stop.

IMAGE: U.S. Border Patrol agents patrol the bed of the Rio Grand in front of where the U.S. Customs and Boarder Protection is housing underage people caught illegally entering the United States at the Tornillo Port of Entry in Guadalupe Bravos, nearby Ciudad Juarez, state of Chihuahua, Mexico on June 19, 2018. (Photo by Brendan Smialowski / AFP via Getty Images)