The state of Texas has taken bold steps to secure its southern border and stem the flow of illegal immigrants across the Rio Grande. It has installed substantial physical barriers along its riverbank and ordered individuals attempting to wade ashore to turn around and return to Mexico. It has enacted legislation authorizing state police to apprehend and deport illegal immigrants. These steps have triggered a heated debate over the legal authority of a state to deal with immigration issues considered by many to be the exclusive responsibility of the federal government. 

In 2012, in Arizona v. United States, the U.S. Supreme Court ruled that it was unconstitutional for states to interfere with the federal enforcement of immigration laws. To prevail in the currently unfolding litigation, Texas must establish that its situation and applicable law are distinguishable from the Arizona case. Texas is attempting to do just this by highlighting the absence of federal immigration enforcement activities, and by emphasizing that the massive flow of unvetted illegal immigrants across the southern border presents a serious threat to national security that justifies state action under constitutional provisions that override immigration statutes. 

Texas defends its recent actions by pointing to provisions in the Constitution that obligate the federal government to protect the states from invasion, and that reserve to the states the right to defend themselves from invasion if the federal government fails to do so. Texas argues that, in light of the manifest determination of the federal government not to secure the border, the state has every right to take the steps it has. 

Thus, the key legal question to be resolved is whether Texas is in fact suffering an “invasion,” as that term is properly understood in light of the text and original meaning of the relevant constitutional provisions. Several things must be kept in mind when evaluating the arguments made by Texas.

From the first, the Founders saw that providing protection against external threats is a fundamental responsibility of government. As they stated in Article III of the Articles of Confederation: “The said States hereby severally enter into a firm league of friendship . . . for their common defense . . . against all . . . attacks made upon them . . . .” 

The Constitution reaffirmed this responsibility, stating in its Preamble that a fundamental purpose of the new federal government was to “provide for the common defense.” Article IV, Section 4 of the Constitution specifically obligates the federal government to “guarantee to every State in this Union . . . [that it] shall protect each of them against Invasion.” 

The Constitution delegates to the federal government a range of enumerated powers so that it can fulfill its responsibility to provide for the common defense and protect the states against invasion. But this delegation of authority is non-exclusive. As Hamilton explained in Federalist No. 32, “the convention aims only at a partial union . . . State governments would clearly retain all the rights of sovereignty which they before had, and which were not . . . EXCLUSIVELY delegated to the United States.”

Each state, as a government with rights of sovereignty, has retained the right to defend itself against invasion if and to the extent that is required for an effective defense. Article I, Section 10, Clause 3 makes this clear: “No state shall, without the consent of Congress . . . engage in war, unless actually invaded, or in such imminent Danger as will not admit of delay.” Thus, if the federal government fails to fulfill its Article IV, Section 4 responsibility to protect a state against invasion, that state has the retained sovereign right to defend itself. 

It is indisputable that the federal government has failed to secure the border along the Rio Grande and elsewhere. Critics of the actions taken by Texas admit this, but they argue that the movement of migrants across the border, even if their numbers are large and their disorderly entry is unauthorized, is essentially an economic phenomenon that simply cannot be characterized as an invasion. They argue that the Framers’ concern when drafting the Constitution was focused on cross-border incursions launched by the organized armies of foreign governments. 

In fact, the Framers were keenly aware that the country faced a wide variety of external threats, not all of them from foreign governments. As Hamilton put it in Federalist No. 25: “The territories of Britain, Spain, and of the Indian nations . . . encircle the union . . . .” 

The constitutional text of Article I, Section 10, Clause 3 was drawn directly from Article VI of the Articles of Confederation, under which no state could engage in war, “unless such State be actually invaded by enemies, or . . . [be threatened] by some nation of Indians . . . and the danger is . . . imminent . . . nor shall any State grant commissions to any ship or vessels of war . . . unless such State be infested by pirates . . . .”

Our constitutional history is clear. The textual terms “invasion” and “danger” encompass external threats posed by non-state irregular forces and lawless bands like Indians and pirates as well as those posed by hostile foreign governments. 

At least some of the critics of the actions taken by Texas concede that an attack by hostile non-state actors could qualify as an “invasion” for purposes of constitutional interpretation. This concession is appropriate. Our longest war, the War on Terror, has been waged against non-state actors. 

Presumably, these critics would agree that Texas has a right to defend itself against a hostile incursion by Al-Qaeda or other terrorists if the federal government had failed in its responsibility to do so. But terrorists don’t announce themselves before they attack, and the collapse of federal border enforcement has left the state with no means by which to identify and separate the serious security threats from the unvetted mass of migrants surging across the open southern border. 

The available data are not reassuring. According to the America First Policy Institute, at least 1.7 million known “gotaways” have come across the border during the Biden administration. More than 70,000 “Special Interest Aliens” with problematic travel patterns and points of origin have been apprehended, along with hundreds of known or suspected terrorists. FBI Director Wray has testified that “threats that come from the other side of the border are very much consuming FBI field offices.” Communist China’s key role in fueling the destructive fentanyl crisis is widely acknowledged. The Department of Homeland Security, on page 12 of its 2024 Homeland Threat Assessment, acknowledges that “Terrorists and criminal actors may exploit the elevated flow [across the border] . . . to enter the United States.” 

Texas is facing a life-and-death dilemma. It can defer to its critics and rely for protection on a federal government that has forsaken its responsibility to provide that protection, or it can resort to self-defense and argue that it is authorized by the Constitution to do so. Over the years, many historical figures, Abraham Lincoln and Justice Robert Jackson among them, have observed that the Constitution is not a suicide pact. 

Texas has acted to defend itself and will defend its actions in court. It may or may not prevail in litigation, but it has made a case that it deserves to.

Note from the Editor: The Federalist Society takes no positions on particular legal and public policy matters. Any expressions of opinion are those of the author. We welcome responses to the views presented here. To join the debate, please email us at [email protected].