What Is the Alien Enemies Act and How Could It Be Used?

By Ben Brasch / The Washington Post

12:27 JST, March 16, 2025

U.S. President Donald Trump is attempting to use a wartime presidential power that has gone unused for eight decades in an effort to fulfill his campaign promise to deport millions of immigrants.

Trump announced Saturday that he would begin using the Alien Enemies Act of 1798 to target Venezuelan migrants, citing the danger allegedly posed by the Venezuelan Tren de Aragua gang.

Hours later, a federal judge granted a request from civil rights groups to stop Trump from deporting Venezuelan migrants currently in custody under the act.

Here’s what to know as the legal battle over the law plays out.

What is the Alien Enemies Act of 1798?

The law lets the president skip the usual immigration court process to detain and deport anyone age 14 or older who is from or the citizen of a “hostile nation or government.” This can happen only if the United States has declared war against the hostile nation or, crucially, if the president feels there is any “invasion or predatory incursion” threatened or attempted against the United States.

The idea is that a person from another country would be loyal to their homeland and thus pose a threat if the United States were at war with that nation.

Only Congress can declare war, and Congress has not declared war against Venezuela. Trump has repeatedly framed the movement of immigrants who illegally enter the United States as an “invasion” and has cast immigrants as a violent threat, even though studies show they commit crimes at lower rates than citizens.

The Alien Enemies Act was part of a package of laws created when John Adams was president. Tension with France was high, and the two countries were on the brink of war, said Cody Nager, a historian of early American immigration and research fellow at the Hoover Institution think tank. Back then, if Congress was out of session, lawmakers couldn’t fly back or call in to vote to declare war. Allowing the president leeway to make a move before a war vote is held was designed to get around that.

It is one of four laws known collectively as the Alien and Sedition Acts – and, Nager said, the only one that wasn’t repealed or modified in 1801 or 1802, when Thomas Jefferson was president.

When has this been invoked before?

The Alien Enemies Act has been invoked three times, all when Congress had declared war: during the War of 1812, World War I and World War II.

During the world wars, the law targeted German, Austro-Hungarian, Japanese and Italian immigrants. After the 1941 attack on Pearl Harbor during World War II, a subsequent executive order was used to hold more than 100,000 people of Japanese descent, including many Americans, in incarceration camps. The Civil Liberties Act of 1988, passed by Congress and signed by President Ronald Reagan, apologized to Japanese Americans who were detained and provided reparations.

Politicians who seek to invoke the act to deal with migrants outside the context of war are wrong, said Katherine Yon Ebright, an expert on constitutional separation of powers at the Brennan Center.

“Their proposed reading of the law is at odds with centuries of legislative, presidential, and judicial practice, all of which confirm that the Alien Enemies Act is a wartime authority,” she wrote in an October report. “Invoking it in peacetime to bypass conventional immigration law would be a staggering abuse.”

How would Trump use it?

In his inaugural speech, Trump said he would invoke the act to deploy the “full and immense power of federal and state law enforcement” against foreign gangs and criminals in the United States.

“There’s no need to reach for these rather rarefied provisions,” said Robert Suro, who taught immigration policy at the University of Southern California for 17 years.

Suro said it isn’t clear why Trump would want to use the law to get rid of violent gang members in the United States, because there are so many avenues, such as Immigration and Customs Enforcement, to remove an immigrant breaking the law.

“If they aren’t committing crimes, then you got to reach for stuff like this,” he said.

Whether effective or not, a possibly intended side effect of this law, Suro said, is to scare people into leaving the country voluntarily.

“A large part of the known strategy is to get people scared, people who might not be in any way vulnerable to legal deportation but are going to be afraid,” he said.

Is this legal?

Yes, the president has the power to use the act against citizens or natives of a hostile nation, said Jean Reisz, a law professor at USC and co-director of the USC Immigration Clinic.

But she said this isn’t an easy way to conduct mass deportations because the act allows for people to ask federal courts for relief.

Reisz said an attorney could easily file a habeas corpus petition asking the courts to review whether a person is unjustly imprisoned. This was done in the case of the Venezuelan men sent to the U.S. base in Guantanamo Bay, Cuba, on Feb. 20.

“I think that this is not going to be a really quick thing, but it’s going to require attorneys to file these emergency orders maybe in the middle of the night,” she said.

She said figuring out whether someone is subject to the act requires judges to answer two questions: Is this person Venezuelan? And is the United States at war with Venezuela, or is Venezuela a hostile country trying to invade?

“Given that we’re not at war with anyone, it’s going to be more complicated,” she said.

If attorneys can prove that Venezuela is not on the same side as the gang members, that would make it difficult to deport people, she said.

Who could be affected?

There are a variety of immigration statuses one can have in the United States, including on a student visa or green card or the “Priority Worker and Persons of Extraordinary Ability” work visa. It could be up to the courts to take each of those into account if the immigrant is being subjected to the Alien Enemies Act, said Stephen Vladeck, a Georgetown law professor who has written about the statute.

He said equating someone who has entered the country illegally for personal reasons to being part of an incursion from a foreign nation isn’t correct.

“It’s supposed to be more than a coincidence that the people being arrested, detained and deported are from a particular country,” he said. “ … The notion that they’re invading in the classical armed conflict sense is laughable on its face.”

What rights protect immigrants?

Even when the law was used in the past, Vladeck said, “there’s a rich history during prior declared wars of federal courts looking carefully” at the cases of foreigners facing deportation.

“It’s hard to imagine federal courts being more deferential today than they were at the outset of World War II,” Vladeck said.

To Vladeck, using the law to enact mass deportations will only further gum up the immigration legal system that officials have tried for years to streamline.

“When the only hook that the government is relying upon is citizenship, that seems far afield from what Congress could ever have thought it was authorizing,” he said. “I could understand why politically and colloquially that might be an attractive position, but, in law, words are supposed to matter.”