When top Trump adviser Stephen Miller threatened on May 9 that the administration is “actively looking at” suspending habeas corpus in response to an “invasion” from undocumented immigrants, he was operating on a fringe legal theory that a right-wing faction has been working to legitimize for more than a decade.
“The Constitution is clear — and that of course is the supreme law of the land — that the privilege of the writ of habeas corpus can be suspended in a time of invasion,” Miller said earlier this month in response to a question about Trump’s threat to suspend habeas corpus, the legal right of a prisoner to challenge their detention. Days after Miller’s remarks, Homeland Security Secretary Kristi Noem issued the same warning when a member of a House panel asked her if the number of illegal border crossings meets the threshold for suspending the right. “I’m not a constitutional lawyer,” Noem said. “But I believe it does.”
Hard-liners have referred to immigrants as “invaders” as long as the U.S. has had immigration. By 2022, invasion rhetoric, which had previously been relegated to white nationalist circles, had become such a staple of Republican campaign ads that most of the public agreed an invasion of the U.S. via the southern border was underway.
Now, however, the claim that the U.S. is under invasion has become the legal linchpin of President Donald Trump’s sweeping anti-immigrant campaign.
The claim is Trump’s central justification for invoking the Alien Enemies Act to deport roughly 140 Venezuelans to CECOT, the Salvadoran megaprison, without due process. (The administration cited different legal authority for the remaining deportees.) The Trump administration contends they are members of a gang, Tren de Aragua, that Venezuelan President Nicolás Maduro is directing to infiltrate and operate in the United States. Lawyers and families of many of the deportees have presented evidence the prisoners are not even members of Tren de Aragua.
The contention is also the throughline of Trump’s day one executive order “Protecting the American People Against Invasion.” That document calls for the expansion of immigration removal proceedings without court hearings and for legal attacks against sanctuary jurisdictions, places that refuse to commit local resources to immigration enforcement.
So far, no court has bought the idea that the U.S. is truly under invasion, as defined by the Constitution or the Alien Enemies Act, on the handful of occasions the government has used the argument to justify supercharged immigration enforcement. Four federal judges, including one Trump appointee, have said the situation Trump describes fails to meet the definition of an invasion. Tren de Aragua “may well be engaged in narcotics trafficking, but that is a criminal matter, not an invasion or predatory incursion,” U.S. District Judge Alvin Hellerstein wrote. Indeed, Trump’s own intelligence agencies found that Maduro is not directing the gang. The Supreme Court has not ruled on the question but froze any more deportations without due process on May 16.
The Trump legal push has been in the works for years. After Trump left the White House, two of his loyalists, former Homeland Security official Ken Cuccinelli and his now-two-time budget chief Russell Vought, quietly built a consensus for the invasion legal theory among state Republican officials and ultimately helped persuade Texas to give it a test run in court.
Most legal scholars reject the idea that the wave of undocumented immigration fits the original definition of what an invasion is, but they worry nonetheless. When U.S. District Judge Stephanie L. Haines, a Trump appointee, issued a preliminary ruling earlier this month that allowed Trump to invoke the Alien Enemies Act, she did not label immigrants “invaders.” Instead, she proposed that Tren de Aragua was “the modern equivalent of a pirate or a robber.”
If the Supreme Court ultimately takes up the invasion question, a ruling like Haines’ offers a blueprint for sidestepping the issue while giving Trump what he wants, or for embracing the invasion theory wholesale, legal scholars said.
“All this really comes down to the issue of whether the United States Supreme Court is going to allow a president to behave essentially as an autocratic dictator if he’s prepared to make entirely fictitious factual declarations that trigger monarchical power,” said Frank Bowman, a legal historian and professor emeritus at the University of Missouri School of Law.
Under the Constitution, if the United States is invaded, Congress has the power to call up the militia and can allow the suspension of habeas corpus, the constitutional right that is the core of due process. The states, which are normally forbidden from unilaterally engaging in war, can do so according to the Constitution if they are “actually invaded.”
The Alien Enemies Act, an 18th century wartime law enacted during a naval conflict with France, also rests on the definition of an invasion. It allows the president to expel “aliens” during “any invasion or predatory incursion … by any foreign nation or government.” It has only ever been invoked three times, during the War of 1812 and World Wars I and II.
Habeas corpus has likewise been suspended only a handful of times in the Constitution’s nearly 240-year history, including during Reconstruction, to put down violent rebellions in the South by the Ku Klux Klan; in 1905, to suppress the Moro uprising against U.S. control of the Philippines; and in Hawaii after Pearl Harbor in order to place Japanese Americans under martial law. In each of these cases, the executive branch acted after receiving permission from Congress.
An exception was in 1861, when President Abraham Lincoln unilaterally suspended habeas corpus at the outbreak of the Civil War. This provoked a direct confrontation with Supreme Court Chief Justice Roger Taney, who ruled that only Congress was empowered to take such an extraordinary step. Congress later papered over the conflict by voting to give Lincoln the authority for the war’s duration.
Today, nearly every historian and constitutional scholar is in agreement that, when it comes to suspending habeas, Congress has the power to decide if the conditions are met.
“The Constitution does not vest this power in the President,” future Supreme Court Justice Amy Coney Barrett wrote in 2014. “Scholars and courts have overwhelmingly endorsed the position that, Lincoln’s unilateral suspensions of the writ notwithstanding, the Constitution gives Congress the exclusive authority to decide when the predicates specified by the Suspension Clause are satisfied.” Even then, the Constitution only allows Congress to act in extreme circumstances — “when in Cases of Rebellion or Invasion the public Safety may require it.”
Ilya Somin, a law professor at George Mason University who has closely followed these arguments, argues there is virtually no evidence that the drafters of the Constitution thought of an “invasion” as anything other than the kind of organized incursion that would traditionally spark a war.
“The original meaning of ‘invasion’ in the Constitution is actually what sort of the average normal person would think it means,” Somin said. “As James Madison put it, invasion is an operation of war. What Vladimir Putin did to Ukraine, that’s an invasion. What Hamas did to Israel, that’s an invasion. On the other hand, illegal migration, or drug smuggling, or ordinary crime — that’s not an invasion.”
In 1994, Florida Democratic Gov. Lawton Chiles Jr. filed the first modern-day lawsuit arguing otherwise. The Haitian and Cuban refugee crises had spawned a new wave of anti-immigration sentiment, and hard-liners accused the federal government of owing states billions for handling immigrants’ supposed crimes and welfare claims. Chiles, who died in 1998, took the concept one step further. He filed a $1.5 billion suit claiming the U.S. had violated the section of the Constitution stating the federal government “shall protect each [state] against Invasion.”
Federal courts slapped down his lawsuit — and a spate of copycatsuits from Arizona, California, New York and New Jersey — and the legal case for calling immigration an invasion died out.
In the late 2000s, a group of far-right voices began to revive this approach. Ken Cuccinelli was among the first and most strident. He was an early member of State Legislators for Legal Immigration, part of a powerful network of anti-immigration groups that pioneered efforts like ending birthright citizenship. The organization contended that immigrants were “foreign invaders” as described in the Constitution.
Cuccinelli evangelized for the theory as he rose from a state legislator to an official in Trump’s first Department of Homeland Security.
“Under war powers, there’s no due process,” Cuccinelli told Breitbart radio shortly before his appointment in the first Trump administration. “They can literally just line their National Guard up with, presumably with riot gear like they would if they had a civil disturbance, and turn people back at the border. … You just point them back across the river and let them swim for it.”
Cuccinelli got traction after Trump’s reelection loss. He joined a think tank Vought had founded as its immigration point man. During his time in the first Trump administration, Vought became frustrated that the president’s goals were frequently thwarted. He founded the Center for Renewing America, dedicated to a sweeping vision of remaking the government and society — what ultimately became Project 2025.
In remarks to a private audience at his think tank in 2023, Vought, who is now Trump’s budget chief and the intellectual force behind Trump’s unprecedented executive power grab, said he specifically championed the term “invasion” because it “unlocked” extraordinary presidential powers.
“One of the reasons why we were very, so insistent about coming up with the whole notion of the border being an ‘invasion’ because there were Constitutional authorities that were a part of being able to call it an invasion,” Vought said. Documented and ProPublica obtained videos of Vought’s speech last year. Vought and Cuccinelli did not respond to requests for comment.
In 2021 and 2022, Cucinelli, with Vought’s help, mounted press conferences and privately urged Gov. Doug Ducey of Arizona and Gov. Greg Abbott of Texas to proclaim that their states were being invaded.
After Arizona’s then-attorney general, Mark Brnovich, released a legal opinion in February 2022 proclaiming violent cartels had “actually invaded” and opened the door for Ducey to deploy the state’s National Guard, Vought bragged to his audience that he and Cuccinelli had personally provided draft language for the opinion. In a previous email to ProPublica, Brnovich acknowledged speaking to Cuccinelli but said his opinion was “drafted and written by hard working attorneys (including myself) in our office.”
Ducey never acted on the invasion theory. But Abbott was more receptive. He invoked the state’s war powers, citing the “actually invaded” clause, in a 2022 open letter to President Joe Biden. “Two years of inaction on your part now leave Texas with no choice,” he wrote. Andrew Mahaleris, a spokesperson for Abbott, said the governor “declared an invasion due to the Biden Administration’s repeated failures in upholding its constitutional duty to secure the border and defend states.”
Abbott ordered the banks of the Rio Grande river to be strung with razor wire and a shallow section to be obstructed by a 1,000-foot string of man-sized buoys and blades and signed a law, S.B. 4, giving state authorities the power to deport undocumented immigrants.
When the Justice Department sued, Abbott’s administration argued in legal briefs that its actions were justified in part because his state was under “invasion.” Twenty-three Republican attorneys general filed a brief in agreement.
“In both scope and effect, the wave of illegal migrants pouring across the border is like an invasion,” their brief read. “The Constitution’s text, the principle of sovereignty in the federal design, and the broader constitutional structure all support the conclusion that the States have a robust right to engage in self-defense. Contained within that right is presumptively acts to repel invasion.”
Texas’ invasion argument did not prevail. The 5th Circuit has blocked S.B. 4., and a lower court and a three-judge panel skewered Abbott’s constitutional argument in the buoy case. In 2024, the full 5th Circuit ruled under another law that Abbott was entitled to leave the floating barriers in place. It avoided ruling on Texas’ invasion claim altogether — but not without one judge dissenting. Trump appointee James Ho argued courts have no ability to second-guess executives about which threats rise to the level of an invasion and justify military action.
In his speech, Vought credited “the massive take-up rate” of the invasion legal theory to his and Cuccinelli’s behind-the-scenes efforts. Now the concept is being taken seriously by the president’s top advisers as they threaten to upend a core civil liberty.
“The definition of ‘invasion’ has broad implications for civil liberties — that’s pretty obvious,” Somin said. “They’re trying to use this as a tool to get around constitutional and other legal constraints on deportation and exclusion that would otherwise exist. But they also want to use it to undermine civil liberties” for U.S. citizens.
Molly Redden is covering legal affairs and how the second Trump administration is attempting to reshape the legal system. You can send her tips at molly.redden@propublica.org or via Signal at mollyredden.14.