A federal judge has ordered an immediate hold on efforts by President Donald Trump to quickly deport Venezuelan nationals under rarely used wartime powers intended to resist a foreign invasion — and demanded the return of planes already headed to Central America.

U.S. District Judge James Boasberg on Saturday ordered the Trump administration to immediately halt efforts to remove those Venezuelan migrants until he has more time to consider whether Trump’s use of the Alien Enemies Act was illegal.

The lawsuit, brought on behalf of five named Venezuelan immigrants, was provisionally turned into a class action — meaning it serves as a block on deportation of all non-citizens in U.S. custody who are subject to Trump’s proclamation invoking the rarely-used law.

“Any plane containing these folks that is going to take off or is in the air needs to be returned to the United States however that is accomplished,” Boasberg announced. “Make sure it’s complied with immediately.”

Two aircraft believed to be carrying Venezuelan deportees took off from an airport in Harlingen, Texas, during a break in a video hearing Boasberg conducted Saturday for the lawsuit filed by immigrant-rights advocates. According to flight tracking databases, one plane was bound for San Salvador, El Salvador, and the other for Comayagua, Honduras, and they were in the air nearing their destinations as Boasberg issued his order.

Boasberg said there are serious legal questions about Trump’s rationale for invoking the 1798 law — used only three times in American history — by labeling the criminal gang Tren de Aragua the equivalent of a foreign government.

The temporary restraining order granted by Boasberg will expire in 14 days, which he said would be enough time to litigate the legality of Trump’s order. He set a further hearing on the merits of the case for late next week.

“Today was a horrific day in the history of the nation, when the President publicized that he was seeking to invoke extraordinary wartime powers in the absence of a war or invasion and claiming virtually unlimited authority to remove people from the country. But, tonight the rule of law prevailed,” said Skye Perryman, president and CEO of Democracy Forward, a national legal organization.

Trump’s proclamation — which was released by the White House Saturday afternoon but signed Friday — relies on the Alien Enemies Act of 1798, which is meant to quickly remove foreigners during wartime or invasion, and comes hours after a preemptive order from a federal judge barred the five Venezuelan nationals from being deported immediately. It’s the latest sweeping executive action from the White House designed to speed up Trump’s efforts to deport millions of undocumented immigrants from the country. The Justice Department argued that the president could unilaterally determine who poses a significant risk to the United States given his inherent authority as president over national security.

“I find and declare that TdA is perpetrating, attempting, and threatening an invasion or predatory incursion against the territory of the United States,” Trump wrote in his declaration.

The order directed Attorney General Pam Bondi to sign a letter within 60 days declaring this U.S. policy, and for the letter to be sent to every judge, including the justices on the Supreme Court, as well as the governor of every state.

Every immigrant that meets the description outlined in the order “are subject to immediate apprehension, detention, and removal.” It is not clear how many members of Tren de Aragua are currently in the United States — or how the government will make such designations.

Trump repeatedly suggested during his campaign he may turn to the Alien Enemies Act to aid his mass deportation plans, a promise he reiterated on Inauguration Day. The president said on Jan. 20 that he would use the wartime law to “direct our government to use the full and immense power of federal and state law enforcement to eliminate the presence of all foreign gangs and criminal networks bringing devastating crime to U.S. soil, including our cities and inner cities.” He also moved last month to designate eight Latin American cartels, including Tren de Aragua, as foreign terrorist organizations.

“We’ll be reading a lot of stories tomorrow about what we’ve done with them,” Trump said at the Justice Department on Friday, speaking about Tren De Aragua. “You’ll be very impressed, and you feel a lot safer, because they are a vicious group.”

Hours before the president’s proclamation was published online, Boasberg issued an urgent ruling blocking the deportations of the five named plaintiffs in the suit. He cited “exigent circumstances” and scheduled a hearing on the issue for later in the afternoon.

The lawsuit, filed by Democracy Forward and the ACLU, emphasizes that the Alien Enemies Act has only been invoked during wartime — the War of 1812, World War I and World War II. The initial order by Boasberg was issued with unusual urgency, before the Trump administration had a chance to respond.

The administration quickly appealed both of Boasberg’s orders to the D.C. Circuit Court of Appeals.

In a motion seeking an emergency stay of his first order, the Justice Department said the argument over the use of the Alien Enemies Act was hypothetical and “fundamentally a political question to be resolved by the President.” At the time of that filing, Trump had already signed the Alien Enemies Act proclamation, but it had not yet been released by the White House.

Immigrant-rights advocates said Trump’s order could subject “countless Venezuelans” to “imminent risk of deportation without any hearing or meaningful review.”

The centuries-old law allows the government to arrest, detain and deport undocumented migrants over the age of 14 who come from countries threatening an “invasion or predatory incursion” of the United States.

Those targeted under the wartime law would be swiftly deported and would not be allowed to have an asylum interview or an immigration court hearing. They would instead be detained and deported with little due process.

“There is so much urgency here, and so much harm at stake,” said ACLU attorney Lee Gelernt, who is representing the Venezuelan nationals, at a Saturday hearing. “The government appears to be moving planes very rapidly, our understanding is that planes are going right now.”

Flight tracking databases showed several flights scheduled to depart from Valley International Airport in Harlingen on planes operated by a company that contracts with Immigration & Customs Enforcement to do deportation flights.

Video posted online Saturday showed a bus departing the El Valle detention center in Raymondville, Texas, accompanied by law enforcement vehicles. Immigration lawyer Jaime Diez said he recorded the images of immigrants from being transferred for deportation under high security just after 2 p.m. Central Time Saturday.

“There was a helicopter following them,” Diez said. “There was a lot of activity going down there …. here was a showing of force to make sure nothing happened.”

Earlier Saturday, Diez won an order from a federal judge in Brownsville, Texas, barring the deportation of Venezuelan Daniel Zacarias Matos. According to a court filing, Zacarias Matos was told Friday he was being taken to the airport to be deported “due to an order from the President,” but the flight didn’t take off because “it did not pass an inspection.”